EPA-650/2-74-037-Q
May 1974
Environmental Protection Technology Series
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EPA-650/2-74-037-0
DISPOSAL OF BY-PRODUCTS
FROM NON-REGENERABLE FLUE GAS
DESULFURIZATION SYSTEMS:
INITIAL REPORT
by
J . Rossoff and R. C. Rossi
The Aerospace Corporation
Urban Programs Division
2350 £1 Segundo Boulevard
El Segundo, California 90009
Contract No. 68-02-1010
ROAP No. 21ACX-AD
Program Element No. 1AB013
EPA Project Officer: Julian W. Jones
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
May 1974
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This report has been reviewed by the Environmental Protection Agency
and approved for publication. Approval does not signify that the
contents necessarily reflect, the views and policies of the Agency,
nor does mention.of trade names or commercial products constitute
endorsement or recommendation for use.
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ACKNOWLEDGMENTS
Appreciation is acknowledged for the guidance and assistance
provided by Mr. Richard D. Stern, Chief of the Regenerable Processes
Section, Control Systems Laboratory who was the EPA Project
Officer during the period covered by this report.
The following technical personnel of The Aerospace Corpora-
tion made valuable contributions to the study performed under this
contract.
L. J. Bornstein R. H. Jones
F. D. Hess W. K. Stuckey
/
C
Ronald C. Rossi, Acting Head
Materials Analysis Department
Materials Sciences Laboratory
Jerome Rosso!
^Director
Office of Pollution and Monitoring
Approved by:
Sru lura, Associate Group
Director
Environmental Programs Group
Directorate
Joseph Meltzer, Group D|peTctor
Environmental Programs Group
Directorate
in
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FOREWORD
This initial report, prepared by The Aerospace Corporation
for the Environmental Protection Agency, Control Systems Laboratory,
Research Triangle Park, North Carolina, presents the results of the
first year's work on a study to characterize power plant sludges from
nonregenerable flue gas desulfurization processes and to assess and
identify methods of sludge disposal that are economically feasible and
environmentally sound. At this time all tasks have proceeded through
the initial stage of completion and all are continuing into the second
year of the current contract.
The study results are given in the Highlights, which briefly
present all significant study findings. Section 1 of the body summarizes
the total study effort for the first year, and Section 9 describes program
status and plans. The other sections present detailed discussions of
all work performed, and provide all related data. These discussions
cover: (a) the test data and analyses of laboratory characterizations,
physical property determinations, and toxicity assessments of selected
sludges; (b) technical and economic surveys and assessments of dis-
posal methods including both ponding of untreated sludges and landfill-
ing of chemically treated (fixed) sludges; and (c) reviews of related
criteria for water quality and solid waste disposal. The appendices
include a listing of companies and individuals contacted for data ac-
quisition, and all backup information relative to the study.
Work completed through November 1973 is reported.
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ABSTRACT
This report describes the initial phase of a study: to
identify potential environmental problems that may be associated with
sludge disposal from non-regenerable power plant flue gas desulfur-
ization systems; to assess potential methods for sludge disposal; to
assess technologies and attendant economics for eliminating or
minimizing potential environmental problems related to sludge dis-
posal; and to make recommendations for sludge disposal. It includes
the following results: laboratory chemical and physical analyses of
limestone sludges from two plants, one burning eastern coal and the
other, western; a review of power plant sludge production and disposal
plans; a survey of pond lining techniques and economics; technical and
economic surveys of sludge chemical fixation processes which treat
the sludge to produce a suitable landfill material; and a review of
water quality and solid waste management regulations.
The report, which discusses the first year's progress
on a continuing study, documents the work completed through
November 1973.
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HIGHLIGHTS
A previous EPA study conducted by The Aerospace
Corporation and subsequent EPA and Aerospace studies showed that
the near-term projected market for structural products and applica-
tions that could use sulfur sludges as an ingredient would consume
only a minor portion of the forecast total sludge production. There-
fore, emphasis in this study is directed toward disposal rather than
commercial applications. Specifically, this study is being conducted
to: (a) identify potential environmental problems that may be associ-
ated with sludge disposal from nonregenerable (throwaway) power plant
flue gas desulfurization systems, (b) assess disposal methods for
sludges including technologies and attendant economics for the elimina-
tion or minimization of potential environmental problems related to
sludge disposal, and (c) make recommendations for sludge disposal.
This study does not evaluate the products of regenerable desulfuriza-
tion systems.
The initial study phase has been completed and accom-
plished the following: (a) laboratory chemical and physical
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characterization of limestone sludges from two plants; (b) reviews of
power plant sludge production, disposal programs, and plans; (c)
surveys of pond lining techniques and economics; (d) technical and
economic surveys of chemical fixation processes that condition the
sludge to prevent leaching problems at disposal sites by decreasing
the permeability and/or solubility of the sludge; (e) reviews of water
quality and solid waste management regulations; and (f) consultations
with individuals in industry, research, education, and governmental
agencies.
As a result of chemical and physical characterization
of selected limestone sludges (sludges from two plants were analyzed
--one burned eastern and one burned western coal), the Aerospace
analyses identified the presence of trace heavy metals in soluble
phases and found significant quantities of dissolved solids, primarily
sulfates. In addition, quantitative data were produced that define
the large amount of water retention in sludges. Sludge characteristics
vary considerably depending on material properties and system appli-
cations (e.g., coal chemistry including sulfur content, reactant and
system water chemistry, scrubber operating conditions, ash content,
and sludge pH). Indications are that raw sulfur sludge disposal in
ponds or landfills of the type used for fly ash disposal may pose an
environmental problem if they are discharged to streams or allowed
to seep through soils to ground water. Also, it appears that raw
sludge disposal sites will be unusable as structural or nonstructural
landfill unless chemically or physically treated because of the water
retention property of the sludges.
Preliminary assessments based on industrial and
government programs to develop environmentally sound sludge dis-
posal methods have shown that several technologies exist that may allow
disposal without causing water pollution as defined by state water quality
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standards or federal drinking water standards; some should produce
reclaimable disposal sites. Chemical fixation appears to be the most
technically advanced environmentally sound disposal method. Another
promising technology, the use of lined ponds, may prevent water
pollution for a limited time; however, additional study will be required
to ensure permanent protection against water pollution and to permit
land reclamation, if desired. The total capabilities of these and the
other methods and their attendant costs are to be determined.
Study highlights are presented in this section. These
findings may change or be refined during this year's study because of
the following: expansion of the technology associated with sludge
production and the many facets of sludge disposal, continuation of the
current study including analyses of samples from other sources, and
assessment of additional disposal technologies. These potential
changes or refinements of the study findings should result in firm
definitions of sludge assessments and disposal techniques and econom-
ics that, when properly related, should be generally applicable to the
power industry.
Highlights of the current study findings are as follows:
1. Ponding Without Environmental Protection
Sludge disposal in a pond without providing envi-
ronmental protection (such as chemical fixation, impervious liners,
or the equivalent) against seepage to water supplies constitutes a
potential water quality hazard. The degree of hazard characteristic of
each site varies depending on the weather, topography, soil charac-
teristics, and proximity of ground and surface waters to the disposal
site. In addition, there exist a significant number of other disposal
variables (e.g., chemical constituents of the sludge and the condition
of sludge disposal) that may impact the potential hazard posed by such
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a sludge pond. The potential problems attendant with these conditions
are to be determined.
2. Water Quality and Solid Waste Disposal Standards
Currently no water quality or solid waste manage-
ment standards specifically apply to power plant sludge disposal per
se. However, state water quality standards that are approved by the
Federal Environmental Protection Agency, are generally applied by
state regulatory authorities to the regulation of sludge disposal. This
is effected by referring to, or repeating directly, the limitations im-
posed by the United States Public Health Service (USPHS) Drinking Water
Standards - 1962. The use of drinking water standards as a criteria
to judge the potential impact of sludges on water quality may be conser-
vative in many cases because a significant reduction of undesirable
constituents in the sludge liquors may be obtained through the attenua-
tion capacity of soils (ion exchange). The ion exchange effect applies
whether or not dilution effects are considered. The degree of con-
servatism that may exist depends on the chemistry of the materials
involved and the disposal site characteristics mentioned in Highlight
No. 1.
The state standards will be modified by require-
ments of the Federal Water Pollution Control Act Amendments of
1972 that control all waters including ground waters of the United
States and that call for new water quality regulations relative to specif-
ic industries, including the power industry. Since it was not known
what the new standards will be, assessments were made of the potential
sludge disposal hazards with respect to the available water quality stan-
dards as specifically applied to drinking water supplies. Based on the
characteristics of sludges analyzed or reviewed in relation to these
Xll
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drinking water standards, it is believed at this time that the direct
discharge of sludges or any portion thereof to surface waters will not
be allowed. Because of a lack of adequate data on the filtering effect
of soils on sludge liquors, it is further believed that measures will be
required to prevent sludge liquors from leaching through the soil to
ground and surface waters.
3. Physical Properties of Sludges
Sludges produced by scrubbing flue gases from
eastern and western coals showed variations in physical properties de-
pending principally on the sulfate/sulfite chemistry and the ash content.
Typically, sludges tend to retain large quantities of water and are diffi-
cult to dewater. They shrink when dried, return to their original wet
volume when rewetted, and can be compacted only when dried below a
saturation value unique to each sludge. Sludge permeability is rela-
tively similar to that of soils; it ranges from silty sands to sandy
-3 -5
clays (10 to 10 cm/sec). However, in contrast to soils that will
freely drain, percolation of waters through sludge will only occur when
a hydraulic head exists over the liquor saturated solids. Based on the
analysis of a limestone/eastern coal sludge, it is indicated that the
sludge will support personnel when the solids content is greater than
65 percent, will support motorized equipment when solids are greater
than 70 percent, and can be pumped when solids are less than 60
percent.
4. Dissolved Solids
The sludges produced by flue gas desulfurization
from power plants contain a wide variety of soluble elements. The
soluble contents of the sludge liquors are typically 2 percent, but can
exceed 10 percent. The soluble ions that constitute the total dissolved
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solids are predominately calcium, magnesium, sodium, sulfate, and
chloride that exist in concentrations individually or totally in excess
of the concentrations allowed in most drinking water standards.
5. Sources of Trace Elements
Coal was found to be the primary source of trace
elements in the sludge liquors, but contributions of specific trace
elements are also made by limestone and make-up water. Some of
these elements (e.g., beryllium, chromium, copper, and lead) enter
the system by the collection of fly ash in the scrubber; other elements
(e.g., chlorine, cadmium, mercury, and zinc) are scrubbed from the
flue gas in the gaseous state. Arsenic, boron, and selenium are
suspected to enter the scrubbing system as fine and ultrafine particul-
ates that are normally too fine to be collected in electrostatic precipi-
tators, but are collected in part by the scrubber.
6. Potential Toxicity
Based on the USPHS Drinking Water Standards,
several trace metals found in the untreated scrubber liquors are pre-
sent in excessive concentrations; however, it is not definite from the
data obtained so far whether or not a real hazard exists. Because of
its relative toxicity, mercury is considered to present the greatest
potential problem. Other trace metals found in scrubber liquors,
such as arsenic, selenium, and lead are present in excessive concen-
trations based on drinking water standards, but at a given concentra-
tion they are less of a problem than mercury. Other constituents
(e.g. boron and chloride) not normally considered hazardous to hu-
mans in concentrations found in the sludge liquors could be harmful
to plant life.
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7. Reduction of Toxicity Potential
The toxicity potential of sludge liquors can be
reduced through scrubber system chemical additions and operating
alternatives to produce a more alkaline liquor having a low oxidation
potential. Other methods of detoxification might include chemical
conditioning of the sludge or water treatment of the liquor. The re-
lative cost effectiveness of these methods must be evaluated.
8. Conditioning for Environmentally Sound Disposal
Chemical fixation is the most technically advanced
of the several methods available for conditioning sludge to reduce its
potential for creating an environmental problem. By reducing the
permeability and/or solubility of the sludge, it appears to effectively
restrict the loss of soluble components through leaching, and provide
a material suitable for landfill and in some cases for structural fill.
In addition, sludge drying, sintering, or mixing with nonchemical
additives such as soil may produce environmentally acceptable results.
However, additional evaluation of these techniques is necessary to
determine long-term stability for pollution prevention.
9. Pond Lining
A survey of pond liners, based on industrial ex-
perience with ponding of chemical and mining sludges and with cooling
system waters, indicates that raw sludges probably can be adequately
contained for the operating life of the scrubber system. Many polyvinyl
chloride liners used in water retainment ponds are still operable after
20 years of service. Manufacturers of other types of flexible liner
materials are currently guaranteeing their products for a service life
of 20 to 25 years. Nonflexible liners (e.g., clay) are reported to have
a service life beyond 25 years. However, the effects of the chemical
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and physical properties of scrubber sludges on the sealing qualities of
pond lining materials over long periods of time need to be determined.
Although the existing technology can control seepage from operational
lined ponds, practical methods need to be determined to control see-
page from a lined pond that has exceeded its operational service life
or to reclaim the pond for land usage.
10. Disposal Costs
The cost of wet sludge (50 percent solids) disposal
by chemical fixation has been estimated based on quotations made by
industry. Reasonable costs (excluding major development impacts)
vary from $1.50 per wet ton by chemical processors to $7.25 per
wet ton by one power plant operator. The costs are affected by many
variables such as: sludge characteristics and chemistry including
water and ash content; transport distances; land values, ownership,
and residual value; type of capitalization; and type of chemical fixa-
tion. Because of these variables, a wide range of costs is to be
expected for disposal by chemical fixation. Except for unusual condi-
tions, it appears that fixation disposal costs for typical cases should
range between $2.50 to $5.00 per ton of wet sludge. As an example of
disposal costs in terms of power produced, fixation at $5.00 per wet
ton (including ash) will be approximately 1. 1 mills per kWh.
Estimates were also made of the cost of disposal
in lined ponds. Variations in disposal costs are caused by factors such
as: type of liner; pond configuration; transport distance; land cost,
ownership, and residual value; type of financing; and time-scaling
of pond construction (e.g. , build a portion now and the remaining
portion(s) later). Preliminary estimates indicate that ponding dis-
posal will cost approximately half that of disposal by chemical fixation.
However, some undetermined costs will be incurred to account for
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leachate protection after the pond is retired, and to dewater the pond
if the land is to be reclaimed; whereas, chemical fixation is intended
to provide permanent environmental protection. Some additional
costing will be required for both disposal methods when the dumpsite
is filled; this is to account for soil cover and/or seeding.
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CONTENTS
ACKNOW LEDGMENTS
2.
:WORD
RACT
LIGHTS
INTRODUCTION AND SUMMARY
1 . 1 Introduction
1 . 2 Summary
1.2. 1 Chemical Characterization and
Crystalline Phase Determination . . .
1.2.2 Sources of Trace Metals of
Interest
1.2.3 Toxicity Assessment
1. 2.4 Detoxification Alternatives
1.2.5 Physical Properties
1.2.6 Raw Sludge and Ash Disposal
Without Controls
1.2.7 Lined Pond Disposal
1.2.8 Sludge Fixation Disposal
1.2.9 Disposal Cost Estimates
1.2. 10 Water Quality and Solid Waste
Disposal Criteria
References
CHEMICAL CHARACTERIZATION AND
CRYSTALLINE PHASE DETERMINATION
2. 1 Sludge Sampling
2.2 Analytical Equipment and Procedures
2.3 Analytical Results
2.4 Analyses and Evaluations
. . v
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ix
1-1
. . 1-1
1-6
1-6
1-9
1-11
1-12
1-13
1-16
1-17
1-21
1-24
1-28
1-35
2-1
2-1
2-2
2-8
2-8
XIX
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CONTENTS (Continued)
2.5 Solubility Appraisal of Potentially
Toxic Elements 2-20
2.6 Source of Potentially Toxic Elements 2-26
2.7 Test Status and Plans 2-28
References 2-30
3. TOXICITY DETERMINATION 3-1
3. 1 Introduction 3-1
3.2 Toxicity Assessment 3-3
3.3 Analyses and Evaluation 3-4
3.4 Status and Plans 3-6
4. DETOXIFICATION POTENTIAL 4-1
4. 1 Toxic Conditions Considered 4-1
4.2 Potential Detoxification Methods 4-2
4.3 Assessment of Potential Detoxification 4-2
4.4 Status and Plans 4-3
5. PHYSICAL PROPERTIES DETERMINATION 5-1
5. 1 Identification and Description of
Samples 5-1
5.2 Physical Property Measurements 5-2
5.3 Analysis and Evaluation 5-22
5.4 Status and Plans 5-26
6. DETERMINATION OF ENVIRONMENTALLY
SOUND DISPOSAL METHODS 6-1
6. 1 Statement of Problem 6-1
6. 2 Potential Disposal Methods 6-5
6.3 Industrial and Government Programs 6-7
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CONTENTS (Continued)
6.4 Raw Sludge and Ash Disposal
Without Pollution Controls 6-15
6.5 Lined Ponds 6-24
6.6 Sludge Conditioning 6-43
References 6-52
7. ENVIRONMENTALLY SOUND DISPOSAL
COST DETERMINATION 7-1
7. 1 Pond Lining and Disposal Cost
Estimates 7-1
7.2 Sludge Conditioning and Disposal Cost
Estimates 7-20
7.3 Cost Comparisons -- Ponding and
Fixation 7-26
References 7-31
8. WATER QUALITY AND SOLID WASTE
DISPOSAL CRITERIA 8-1
8. 1 Summary 8-1
8.2 Regulations 8-7
References 8-16
9. PROGRAM STATUS AND PLANS 9-1
9. 1 Introduction 9-1
9.2 Status and Plans 9-1
APPENDICES
A. COMPANY/AGENCY VISITS OR
COMMUNICATIONS A-l
B. LABORATORY CHEMICAL ANALYSES
ANALYTICAL RESULTS B-l
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CONTENTS (Continued)
C. POND LININGS AND POND CONSTRUCTION
CHARACTERISTICS AND DESIGN FEATURES C-l
D. POTENTIAL COMMERCIAL UTILIZATION OF
SULFUR DIOXIDE SLUDGES D-l
E. COMMENTS ON SELECTED POWER PLANT
SLUDGE DISPOSAL PROGRAMS E-l
F. TOXIC EFFECTS OF TRACE ELEMENTS F-l
G. GLOSSARY G-l
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FIGURES
1-1. Sludge Bulk Densities 1_15
1-2. Installed Liner Costs 1-20
1-3. Sludge Disposal Costs -- Ponding 1-27
2-1. Process Flow Diagram for TCA System at
the Shawnee Power Station 2-6
2-2. Process Flow Diagram for Mohave Station
Limestone Scrubber Pilot Plant 2-7
2-3. Interim Status of Data Development -- Level
of Heavy Metals at Each Sample Point of the
Shawnee Power Station 2-10
2-4. Interim Status of Data Development -- Level
of Heavy Metals at Each Sample Point of the
Mohave Power Station 2-12
5-1. Shawnee Sludge Bulk Densities 5-5
5-2. Mohave Sludge Bulk Densities 5-6
5-3. Viscosity of Shawnee Sludges 5-10
5-4. Viscosity of Mohave Sludges 5-12
5-5. Sludge Compaction Strength 5-15
5-6. Drainability of Shawnee Sludge 5-20
6-1. Typical Pond Features -- Flexible
Liner System 6-27
6-2. Pond with Underdrainage 6-28
6-3. Potash Evaporation Pond Features --
Texasgulf, Inc 6-29
7-1. Relative Costs of Flexible Liners 7-4
xxi 11
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FIGURES (Continued)
7-2. Initial Investment, Total Pond Cost 7-14
7-3. Capital Investment for 3-year Capacity
Pond -- Example for 20-mil-thick PVC
Liner 7-16
7-4. Sludge Disposal Costs -- Ponding 7-19
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TABLES
1-1. Representative Trace Element Analysis 1-8
1-2. Pond Liner Material Characteristics 1-19
1-3. Comparison of Trace Element Analyses
Between Raw Sludge and Leachate from
that Sludge After Chemical Conditioning
by Fixation 1-22
1-4. Sludge Fixation Costing Estimates 1-25
1-5. Disposal Cost Comparisons -- Sludge
Including Ash; 50 Percent Solids 1-29
1-6. Excerpts from United States Public Health
Service Drinking Water Standards - 1962 1-31
1-7. Summary Sludge Liquor Metal Analysis
Compared to Water Quality Criteria 1-34
2-1. Sludge Samples Acquisition, Shawnee
Power Station, 1 February 1973 2-3
2-2. Sludge Samples Acquisition, Shawnee
Power Station, 11 July 1973 2-4
2-3. Sludge Samples Acquisition, Mohave
Power Station, 30 March 1973 2-5
2-4. Relative Solubilities in Weakly Alkaline
and Reducing Solutions 2-22
6-1. Planned and Operating Flue Gas Desulfuriza-
tion (FGD) Units on U.S. Power Plants as of
September 1973 -- Limestone Scrubbing
System 6-9
6-2. Planned and Operating Flue Gas Desulfuriza-
tion (FGD) Units on U.S. Power Plants as of
September 1973 -- Lime Scrubbing System 6-10
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TABLES (Continued)
6-3. Planned and Operating Flue Gas Desulfuriza-
tion (FGD) Units on U.S. Power Plants as of
September 1973 -- Limestone or Lime
Scrubbing System Not Selected 6-11
6-4. Planned and Operating Flue Gas Desulfuriza-
tion (FGD) Units on U.S. Power Plants as of
September 1973 -- Magnesium Oxide
Scrubbing System 6-12
6-5. Planned and Operating Flue Gas Desulfuriza-
tion (FGD) Units on U.S. Power Plants as of
September 1973 -- Other Sulfur Dioxide
Control Systems 6-13
6-6. Planned and Operating Flue Gas Desulfuriza-
tion (FGD) Units on U.S. Power Plants as of
September 1973 -- Process not Selected 6-14
6-7. Ohio Power, Muskingham River Plant Ash
Pond Discharge 6-17
6-8. Pond Liner Material Characteristics 6-33
6-9. Potential Techniques for Monitoring Liquid
Seepage from Ponded Areas 6-34
6-10. Comparison of Trace Elements Analyses
Between Raw Sludge and Leachate from
That Sludge After Chemical Conditioning
by Fixation 6-44
7-1. Sludge Produced as a Function of Power ^
Plant Age and Operating Hours 7-2
7-2. Flexible Liner Cost Data Midpoint Price
Range Value -- Installed 7-5
7-3. Nonflexible Liner Cost Data -- Installed 7-6
7-4. Liner Material Comparisons 7-12
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TABLES (Continued)
7-5. Pond Initial Investment Costs 7-15
7-6. Average Disposal Costs -- 30 Year 7-18
7-7. Sludge Disposal Cost During First Year 7-21
7-8. Sludge Fixation Cost Estimates 7-25
7-9. Disposal Cost Comparisons -- Sludge
Including Ash; 50 Percent Solids 7-29
8-1. Examples of Variations in State Water
Quality Standards 8-3
8-2. Excerpts from United States Public Health
Service Drinking Water Standards - 1962 8-4
8-3. Analysis of Samples Taken from Limestone
Scrubber at TVA Shawnee Station,
Paducah, Kentucky, 11 July 1973 8-6
8-4. Selected State Water Quality Criteria 8-10
XXVll
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SECTION 1
INTRODUCTION AND SUMMARY
1. 1 INTRODUCTION
1.1.1 Background
The removal of sulfur dioxide (SO2) from stack gases
in compliance with provisions of the Clean Air Act and local regula-
tions will require that the electric power industry use special equip-
ment on many existing and new boilers that burn sulfur-bearing fossil
fuels. Currently, the preferred method of SO2 removal (generally
referred to as lime or limestone scrubbing) employs the scrubbing of
the stack gas with a slurry of water and an alkaline earth additive,
principally lime or limestone. This solution reacts with the SO2 and
produces sulfates and sulfites of calcium and magnesium that are
drained from the scrubber. There is no regeneration of the reactants
in these systems. If ash collection devices are used upstream of the
scrubber, the amount of fly ash entrained in the slurry and collected
with the scrubber reaction products will depend on the efficiency of the
collection devices.
A previous study of sludges made by The Aerospace
Corporation for the Environmental Protection Agency (EPA) and other
1-1
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EPA investigations identified the existence of dissolved trace heavy
metals (e.g., arsenic, magnesium, zinc) and high concentrations of
soluble components (e.g., chlorides, sulfates, carbonates) in the
scrubber effluent. From these studies it appeared as if it may not be
acceptable to either discharge the system waters (liquors) and sludges
to water supplies or to allow their percolation through the soil to
ground waters.
The SO2 scrubbing systems that are in use or planned
are designed so that the liquors are not directly discharged to water-
courses, but are recirculated to avoid water pollution. In this
operating mode, called closed loop operation, water leaves the sys-
tem only by evaporation in the scrubber and by association with
disposed sludge. The concern of this study, therefore, is for the
characterization of the disposed material and for its environmentally
sound disposal. Methods generally considered for ultimate disposal
are landfilling and ponding. In both methods, the environmental
considerations are for water quality and the potential reuse of the
large acreage that will be required to contain the sludge. However,
both methods present problems: raw sludge has the potential of
leaching potentially undesirable constituents into water supplies
from landfills and ponds; raw sludge retains water and, therefore,
may not provide strength adequate to allow reuse of the land. Tech-
nologies have been developed to provide disposal techniques that
will solve these problems; however, none of the technologies have
been demonstrated on a large scale over a long period. The more
significant of the technologies that are to be assessed in this study
are: (a) chemical fixation processes that reduce the solubility and/
or permeability of the sludge to minimize or eliminate leachability
problems and that produce a material suitable for landfill, (b) pond
management including the use of linings that provide impermeable
bases, and (c) drying, compacting and covering, or using inert
additives to provide the benefits mentioned in (a).
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A previous Aerospace Corporation study for the
EPA, and other EPA studies strongly indicated that commercial
sludge utilization as predicted today indicate that only a small
portion of the quantities to be produced will be consumed. Based
on that assessment, a characterization and disposal study program
was defined by the EPA for The Aerospace Corporation that would
consist of laboratory characterization, technical and economic
surveys, analyses, assessments, and recommendations.
1.1.2 Objectives
The study objectives are to:
a. Perform chemical characterization and crystalline
phase and physical property determinations of
selected sludges.
b. Perform toxicity determination of selected sludges
and assess methods of detoxification.
c. Evaluate and assess environmentally sound disposal
methods, technology, and costs.
d. Relate sludge disposal to water and solid waste
environmental regulations.
1.1.3 Study Approach
The study objectives are to be met by: (a) charac-
terizing, as appropriate, the sludges, coals, make-up water, fly ash,
and chemically conditioned sludges from specified sources by
chemical and physical analyses; (b) surveying technical and economic
data, as appropriate, pertaining to sludge production, qualities,
and disposal; (c) performing evaluations of all data determined in
(a) and (b); (d) reviewing appropriate water quality standards and
solid waste management regulations, and correlating this study's
technical evaluations with limitations imposed by these regulations;
and (e) identifying environmentally sound disposal techniques on the
basis of technical and economic evaluations.
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1.1.4 Acquisition of Relevant Data
The first year of this study has been completed.
Laboratory analyses have been conducted on two lime stone/eastern
coal sludge samples obtained from the TVA Shawnee Power Station
in Paducah, Kentucky, and one limestone/western coal sample from
the Mohave Station in Clark County, Nevada, provided by the
Southern California Edison Company. Additionally, preliminary
reviews have been made of disposal techniques at the following
power companies: Northern States Power Company, Sherbourne
County Station, Minneapolis, Minnesota; Commonwealth Edison,
Will County Station, Joliet, Illinois; Louisville Gas and Electric
Company, Paddy's Run Station, Louisville, Kentucky; and Duquesne
Light Company, Phillips Station, Pittsburgh, Pennsylvania.
Contacts have been made with several other power stations, EPA
regional offices, and EPA National Environmental Research Centers
(NERC) at Research Triangle Park, North Carolina; Cincinnati,
Ohio; and Corvallis, Oregon. Preliminary reviews have been made
of fixation techniques at Chemfix, Division of Environmental Sci-
ences, Inc., Pittsburgh, Pennsylvania; Dravo Corporation, Pitts-
burgh, Pennsylvania; and International Utilities Conversion
Systems, Inc., Philadelphia, Pennslyvania. A survey has been
made of ponding techniques, and contacts have been made with
various ponding contractors, suppliers, and users. Consultation and
advice have been obtained from Dr. J.E. McKee, Professor of
Environmental Engineering, California Institute of Technology.
Discussions have been held with soil sciences personnel from the
University of Arizona and the Illinois State Geological Survey, both
of whom are supporting the EPA Solid and Hazardous Waste Research
Laboratory at Cincinnati, and with sanitation engineers from munic-
ipalities and the University of California at Riverside. Federal and
1-4
-------
State water quality and solid waste management regulations have
been reviewed, as appropriate.
Because of the varied and changing nature of the
sludge disposal problem and current technological advancements
in industry, all tasks will continue into the second year and
samples will be analyzed from other stations to include additional
types of sludges.
1.1.5 Organization of This Report
Section 1 summarizes the study findings and provides
brief discussions and appropriate tables and figures to support
those findings.
Section 2 describes the analytical equipment and
procedures used to perform the chemical characterization and
crystalline phase determination of sludge samples from two power
plants. It also includes the analyses and evaluations of the
elements selected because of their potential toxicity, an appraisal
of the solubility of these elements, a discussion of the primary
sources of trace elements found in the scrubber sludge, and a
brief statement about test status and plans.
Sections 3 and 4 discuss toxicity determination and
detoxification potential, respectively.
Section 5 describes the measurements made to
determine the sludge's physical properties and its physical behavior
as applied to disposal. The results are analyzed and evaluated to
determine those properties most useful in developing engineering
design criteria for sludge disposal technology.
Section 6 contains the analyses of potential disposal
methods: raw sludge disposal without environmental protection,
lined disposal ponds, and sludge conditioning. The status of
1-5
-------
industrial and government sludge disposal development and
demonstration programs is also assessed.
Section 7 provides pond lining and disposal cost esti-
mates, sludge conditioning and disposal cost estimates, and ponding
and fixation cost comparisons. Water quality and solid waste disposal
criteria are discussed in Section 8, Preliminary estimates are made
of the effect of these criteria on sludge disposal. Program status and
plans are briefly described in Section 9.
Supporting data in the appendices include the identifica-
tion of data sources, laboratory analysis data sheets, pond construc-
tion details, potential commercial utilization of sludges, power plant
disposal program descriptions, and some comments about the poten-
tial toxic effects of trace elements.
Throughout this report, analytical data are given in
units of parts per million (ppm) or parts per billion (ppb). For sim-
plicity of usage, the equivalences of these units are considered to be
as follows:
State
Liquids
Solids
ppm
mg/liter
mg/kg
ppb
Hg/liter
M-g/kg
1.2 SUMMARY
1.2.1 Chemical Characterization and Crystalline
Phase Determination
Three separate sets of samples were obtained that rep-
resent the input and output constituents of the Turbulent Contact Ab-
sorber (TCA) test scrubber at the Shawnee Power Station in Paducah,
Kentucky. These sludge samples were produced by scrubbing flue gas
from eastern coal with limestone. One set of sludge samples was ob-
tained from the TCA prototype scrubber at the Mohave Power Station,
1-6
-------
Clark County, Nevada; it is a sludge produced by scrubbing flue gas
from western coal with limestone.
Sample analyses were performed by emission spectro-
scopy, spark source mass spectroscopy, atomic absorption spectro-
photometry, and ion microprobe mass analysis. Standard techniques
were used for each type of analysis, and concentration values were
determined by comparison with standards prepared for each element.
A representative trace element analysis of Shawnee
Power Station sludge liquors is given in Table 1-1. Concentrations
of the trace metals were determined at various sampling stations in
each system in both the solids and liquid portions of the scrubber
systems (the potential environmental impact of these trace metals is
discussed in Sections 1.2.3, 1.2.4, and 1.2.10).
In addition to these metals, relatively high concentra-
tions of boron and chloride ions were observed in the sludge liquors.
Although these elements do not pose a problem as great as the trace
metals mentioned, their high solubilities create a potential water qual-
ity condition that is not readily abated by current water treatment
practices. Another potential nontoxic problem arises from the oxygen
demand of the sulfite phase that further affects the potential water qual-
ity impact of supernatant or leachate liquors. This chemical oxygen
demand tends to obviate the direct discharge of sludge to streams in
some cases even in the absence of any water quality effects due to
trace elements.
A major potential water quality problem created by
uncontrolled sludge disposal arises from the solubility of the various
trace elements in the sludge. The measured concentration of these
elements in the liquor provides, in a qualitative sense, a measure
of the relative availability of these elements to the environment. A
more quantitative evaluation must take into consideration other
1-7
-------
Table 1-1. REPRESENTATIVE TRACE ELEMENT ANALYSIS
TVA Shawnee Power Station; TCA Limestone Sludge
(parts /million)a
Trace element
Arsenic (As)
Beryllium (Be)
Cadmium (Cd)
Chromium (Cr)
(total)
Copper (Cu)
Lead (Pb)
Mercury (Hg)
Selenium (Se)
Zinc (Zn)
Scrubber system input
Make-up water
<0. 02
0.001
<0.0005
<0. 001
0.01
<0. 005
<0.01
<0.01
<0.2
Limestone
5
3
0.5
10
3
1
1
2
10
Fly ash
20
5
3
15
15
3
4
5
100
System output
(clarifier underflow)
Liquid
0. 2
0.01
0.005
0.05
0.05
0. 1
0. 06
0.3
0. 5
Solids
15
4
3
15
10
1
2
4
50
I
00
Equivalent to mg/liter
-------
factors that take into account the complexity of the chemistry in the
scrubber circuit. Nevertheless, analysis of these data indicate that
those metals with the greatest observed solubility are also those whose
more stable compounds are carbonates or hydroxides. These data
suggest that in a limestone scrubber system, the concentration of
carbonate ions may be inadequate (and the concentration of hydroxide
ions is inadequate) to effectively reduce the concentration of these
metals. Chemical treatment that alleviates this inadequacy is dis-
cussed in Paragraph 1.2.4. In a lime scrubber system the concen-
trations of carbonate and hydroxide ions would be greater, and it is
expected that they would be more effective in reducing the concentra-
tion of trace elements in the liquors.
1.2.2 Sources of Trace Metals of Interest
From the various chemical analyses conducted in this
study, determinations were made of the source or sources of each ele-
ment and the chemical or physical state in which they might be expected
in the sludge.
Arsenic in the sludge originates primarily in coals and
can be found both as the inorganic sulfides and as the organic compo-
nents in the coal. During combustion, compounds of arsenic are con-
verted to oxides and carried in the flue gas to the scrubber where a
mixture of three arsenious acid complexes are formed, the amount
of each depending on the pH. Reaction of these acids with calcium
probably produces the most insoluble compound.
The beryllium occurs in both eastern and western coals.
Beryllium forms both an insoluble hydroxide and sulfate, and it can be
in the sludge probably in either of these forms.
Cadmium usually appears in coals in association with
zinc as the sulfide mineral phase. During combustion, cadmium may
sublime as the element or as the oxide also in association with zinc.
Much of the cadmium is suspected to escape the system in the flue
1-9
-------
gas, but if entrained in the scrubber, several insoluble cadmium
compounds can form.
Chromium enters the scrubber system from the coal,
probably in association with iron as the oxide. It forms an insoluble
hydroxide, and this is probably the form in which it is found in the
sludge.
Copper originates in coal primarily as the inorganic
sulfide phase. It would enter the scrubber as the oxide and would be
immobilized as the hydroxide in the sludge.
Mercury is typically found in eastern coals at levels
somewhat higher than in western coals. Recent studies suggest that
about half of the mercury is organic, the other half is presumed to
be a sulfide. Mercury is either sublimed as the metal or as the sul-
fide, some of which is removed from the flue gas in the scrubber.
Few mercury compounds, except the mercurous chloride, are insol-
uble; this compound may be unstable at points of high oxidation poten-
tial. Limestone and make-up water can also contribute some mer-
cury to the scrubber system.
Lead originates in coals as the sulfide and enters the
scrubber as the oxide. The lead compounds in the scrubber liquor
are all slightly soluble; the sulfate being the most insoluble and prob-
ably the compound in which lead is found in the sludge.
Selenium chemically reacts similar to arsenic and
probably appears in the scrubber much like arsenic. Selenites of
calcium and magnesium are the most insoluble phases and may be
the form in which selenium is precipitated from the liquor.
Zinc is also found in coals. The oxide is the product
of combustion and enters the system either adsorbed onto the particu-
lates or as a sublimed specie. It reacts with hydroxide and carbonate
ions to form insoluble compounds.
1-10
-------
1.2.3 Toxicity Assessment
The determination of heavy element toxicity is
dependent upon the physiological effects of each element on the
natural function of the human body. Many elements existing in nature
in trace quantities are essential to man's life or health. Of the
potentially toxic elements identified in this study, only cadmium,
lead, and mercury have no known biological function and can act
synergistically with other substances to increase toxicity. Once in
the body; their toxic effects are cumulative and are harmful to the
degree that the dosages and resultant concentrations can approach a
lethal threshold. Even those trace elements having proven biological
functions, when ingested at high concentrations, can produce disease
either by their cumulative effect or by inhibition of natural functions.
The primary potential health hazards that may exist
from, power plant sludge arise from the solubility of arsenic and
mercury. Lead and selenium may also be the source of problems
under certain environmental conditions.
Although not found at high concentration in coals, mer-
cury poses the most serious problem because of its relative toxicity.
Arsenic and selenium are both recognized as micronutrients in the
human body; however, their observed availability in the analyzed
sludge liquors surpasses standards for human capacitance. Lead is
like mercury; it serves no useful purpose in the body.
It is not yet possible to determine whether stack-gas
sludge poses a health problem; however, attention is directed to those
potentially toxic elements mentioned, all of which were measured in
concentrations that exceed Public Health Drinking Water Standards.
1-11
-------
For this reason, it appears that sludge disposal should be managed
such that liquor, leachate, or runoff from a sludge disposal site will
not directly intermingle with drinking water supplies.
1.2.4 Detoxification Alternatives
The potential capability for detoxification of a sludge
is a function of the element or group of elements that pose a potential
toxic hazard. The elements identified in the limestone system as
having the capability most likely to create a toxic hazard are arsenic
and mercury, and possibly lead and selenium. Since the potential
toxic hazard from a sludge will originate primarily from the sludge
liquors, leachate, or runoff, detoxification methods must consider
conversion of the potentially toxic components from the liquid phase
to a solid, or by concentration in a smaller liquid volume that can
then be disposed of by other means.
The most technically advanced sludge detoxification
method is the chemical fixation process that coverts sludge from
a highly water-retentive material to one that has properties suitable
for landfill or structural fill. In this conversion process, soluble
components are reported to be chemically combined, and thereby
restricted in their availability to the environment.
The concentrations of the most soluble of the poten-
tially toxic elements in the limestone scrubber liquors may be reduced
by a chemical treatment or system modifications that increase pH
and/or retard oxidation within the scrubber system.
Among the more feasible detoxification schemes is a
water treatment of a liquor side stream in which chemical precipita-
tion (lime softening) may precede a secondary water treatment method.
Among the possible secondary treatments are: reverse osmosis,
flash distillation, electrodialysis, and ion exchange. For any of these
1-12
-------
secondary treatment techniques to be effective, a reduction in total
dissolved solids must precede their use. These processes are
relatively costly; they might be considered cost effective in only
rare circumstances. However, since some of these water treatment
techniques will also reduce the chloride concentration in scrubber
liquors, savings will be realized by their use in corrosion avoidance
of major hardware.
A brine of very high dissolved solids content is a by-
product in some of these water treatment processes. This brine
can be disposed of by chemical fixation processes or by evaporation.
The relative costs of these various processes have
not yet been determined.
1.2.5 Physical Properties
Physical properties were determined from the Shawnee
and Mohave sludges to provide a more complete characterization of
their behavior as related to limitations or restrictions on sludge
disposal, handling, and transportation techniques. In each case, the
sludge was in the state in which it would be normally disposed of
without further processing.
Although these two sludges were the products of scrub-
bing flue gas from eastern and western coals, their behavior was not
a consequence of the coal's geological origin, but rather a conse-
quence of the phase constituents in the sludge. The Mohave sludge
is low in fly ash and very high in sulfate content; whereas the
Shawnee sludge has about a 40 percent fly ash content and a 20 per-
cent sulfate content. Most behavioral differences between the two
sludges can be attributed to the difference in the content of the plate-
like sulfite particles.
1-13
-------
Many of these sludge's physical properties were found
to be strongly dependent on water content; it affects their behavior
either while being handled for disposal or after being placed in a dis-
posal site. For the two sludges, equivalent water content did not pro-
duce equivalent behavior as revealed in the dewatering results (Fig-
ure 1-1). The results are directly attributable to sulfite content and
can be summarized as:
Percent solids
Condition Shawnee Mohave
No drainage 45) ,_
Drain freely 52 J
Centrifugation 55 75
Vacuum-assisted filtration 65 80
If disposed of within a pond, the Mohave sludge will
settle, or if mechanically dewatered, is expected to attain a solids
content great enough to support personnel and should require very
little additional air drying to support equipment. In contrast, the
Shawnee sludge is not expected to settle or mechanically dewater
sufficiently for support of personnel. In either case, sludge support
strength for personnel will not be attained until a solids content
greater than 65 percent is reached; equipment support will require
greater than 70 percent solids. Ponded sludge that has dried will
return to its original wet volume when rewetted.
The drainability of the Shawnee or Mohave sludge is
similar to that of natural soils. The coarseness of the sulfate par-
ticles in the Mohave sludge provides a drainability similar to that of
soils with a high sand content; whereas the Shawnee sludge is more
typical of silty clay soils because of the high sulfite content.
1-14
-------
1.0
20 40 60 80
SOLIDS CONTENT, wei^it percent
100
1.0
20 40 60 80 100
SOLIDS CONTENT, wei^it percent
Figure 1-1. Sludge bulk densities
-------
Neither sludge was found to develop strength during
settling by pozzolanic reaction or other means. The compaction
strength developed during drying or dewatering did not change with
time. Without specific chemical additions, the sludges did not
develop resistance to subsequent leaching.
Based upon viscosity tests, it was determined that
either sludge can be easily pumped at low solids content. As solids
content increases, the viscosity of the Shawnee sludge increases
regularly and could place an increased demand on the pump; its
pumpability appears limited to about 60 percent solids. For the
Mohave sludge, viscosity does not vary much with an increase in
solids content until a value of about 60 percent is reached; then the
viscosity rises rapidly to a point that pump overloading and transfer
pipe plugging are possible.
The sludge corrosiveness appears to be pH dependent,
and no accelerated growth was observed except when a galvanic
reaction was allowed to proceed as a consequence of an oxygen gra-
dient between supernatant liquors and sludge solids. This condition
could cause serious corrosion problems if the sludge were trans-
ported or stored in steel containers.
The physical property test results indicate that a
sludge containing high sulfate content has properties, primarily
dewatering behavior, that are desirable for disposal.
1.2.6 Raw Sludge and Ash Disposal Without Controls
The power industry has several alternative methods
available for disposal of fly ash and sulfur sludge. Presently fly ash
lagoon disposal is contributing to the dissolved solids content of
receiving waters. A majority of the nation's power plants are located
1-16
-------
along the banks of major watercourses and the contribution from each
plant is measured in tons per year. The disposal of ash with sludge
reduces the environmental pollution load by eliminating the discharge
of waste water from the fly ash lagoon, and containing it within a
closed-loop scrubber operation that recirculates the liquor and con-
trols the disposal of separated solids.
If sludge is disposed of in a separate pond, elemental
constituents carried in the flue gas (primarily mercury, cadmium,
zinc, arsenic, and possibly selenium) will be scrubbed from the flue
gas and attain a level of solubility in the pond liquors. By disposing
of the fly ash with the sludge, elements that were found soluble in fly
ash lagoons are additionally available to the scrubber liquors. Although
simultaneous disposal eliminates the continuous disposal of fly ash
lagoon waste waters to watercourses, the additional contribution of fly
ash constituents to these liquors increases the potential environmental
hazard created by the sludge.
Whether sludge and fly ash are disposed of simulta-
neously, a potential environmental hazard will exist. Sludge disposal
without control requires consideration of many conditions that may
contribute to seepage to ground waters or discharge to watercourses:
the soil (sand/clay content), the disposal site's geological and hydro-
logical location, weather, and disposal site management. Other con-
siderations that may affect the potential impact of sludge intrusion into
waters include: the coal's chemical content, scrubber type, and sor-
bent. Even when sludge disposal sites are being controlled (e.g. , by
pond linings or chemical fixation), their effectiveness must be deter-
mined for long periods.
1.2.7 Lined Pond Disposal
Technical reviews were made to evaluate the potential
use of fifteen different flexible and nonflexible materials for lining flue
gas desulfurization raw sludge disposal ponds. The flexible liners
1-17
-------
consist of 10- to 30-mil thick materials such as polyethylene,
polyvinyl chloride, Hypalon, and butyl rubber. Nonflexible liners
include asphalt, cement products, and pozzolans in 3- to 6-in. thick-
nesses, and clay with thicknesses varying from several inches to
several feet. The liner provides a physical barrier to prevent any
seepage of liquors from the disposal ponds into ground or surface
waters. Table 1-2 lists the liners considered, thicknesses normally
employed, permeability rates, and life expectancy. Figure 1-2 pre-
sents the installed costs for the lining materials (disposal costs are
discussed in Section 1.2.9).
Although ponding is currently a proven technique for
large-scale, low-cost evaporation operations and for waste disposal,
the predicted useful life of a potential sludge pond liner still needs
to be defined. It is directly dependent upon the aging characteristics
of the liner material and its chemical interaction, if any, with the
sludge or supporting soil. Flexible liners are generally guaranteed
for 20 to 25 years. The life expectancy of nonflexible liners is esti-
mated to be even greater. However, long-term service data appli-
cable to sulfur sludge containment do not exist for either type of
liner.
The techniques currently available to monitor pond
seepage range from backfilling with sand/gravel to permit the seepage
to be piped to an observation well, to using electromechanical soil-
moisture measuring devices.
Because practical methods to dewater a raw sludge
pond have not as yet been developed, the technologies have not been
adequately defined to control leaching from a lined pond after its
service life. Therefore, the potential for pond reclamation for future
land usage and the considerations necessary for permanent environ-
mental control must be determined.
1-18
-------
Table 1-2. POND LINER MATERIAL CHARACTERISTICS
Material
Flexible
Polyethylene
Polyvinyl chloride
Hypalon
Chlorinated
polyethylene
Petromat fabric
Butyl rubber
EPDM rubber
Polyester fiberglass
Nonflexible
Soil cement
Concrete
Clay
Asphalt concrete
Gunite
Pozzolan stabilized base
Thickness,3
mil
10
10 - 20
30
30
-
30
30
65
.
.
-
-
.
-
in.
-
-
-
.
1/16 - 1/8
-
-
-
6
6
Up to 18
6
3
2 - 6
Permeability,
cm/sec
d
d
d
d
d
d
d
d
About 10"6
About 10'8
10'5 to 10"8
d
d
10"5 to 10"7
Life expec-
tancy, yr
20
20
20 +
20 +
20 +
20
20
20 +
20 +
50+8
50 +8
50+S
20+8
50+8
Dirt
cover"
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
Average installed
cost, $/sq yd
0.70
1. 10 - 1. 50
3. 25
3.25
2. 00
2. 80
4. 00
4. 75
1. 00
3. 75 - 4. 75
1.00 - 6.00
4.00
6. 30
3.85
Notes
e,f
e,f
e,h
e
e,f
aCommonly used
Protection from ultraviolet rays
cSee Section 7. 1
Superior to clay
Affected by wet/dry and hot/cold cycles
Subject to 3 u If ate attack
^Industrial estimates not obtained
Possible breakdown due to ion exchange
To convert
from
sq yd
mil
in.
to
sq m
cm
cm
Multiply
by
0.8361
0. 00254
2. 54
-------
ts)
o
o-
8 3
TO CONVERT:
FROM
sq yd
mil
in.
_ ft
^
1
.
I
~ T JL
n PVC p'
. X 10 mi!2(
PE
10 mil
TO
sq m
cm
cm
m
r
I SOIL
MULTIPLY BY
0. 8361
0.00254
2.54
0.3048
CP
30
(
<
f CEMENT
L6 'zt
/C
) mil
f H
BUTYL
RUBBER
> 30 mil
reTRCMAT
GUNITE
3 in.
T 5
r T 1 POLYESTER T
5111 T A T S'mB61-^ 1
EPDM CONCRETE 1
I 30 mil 6 in- ASPHALT
; g 6 in.
1
HYPALON
30 mil
I
1
POZZOLAN
6 in.
CLAY
UP TO
18 in.
LINERS AND THICKNESS
Figure 1-2. Installed liner costs
-------
1.2.8 Sludge Fixation Disposal
Several sludge conditioning methods are available to
reduce the sludge's potential as an environmental problem. Chemical
fixation is the most advanced method, but other techniques such as
sludge drying, sintering, and blending with nonchemical additives
may be equally effective. However, none of these other techniques
has been extensively developed.
The chemical fixation of power plant sludges produces a
material suitable for landfill and a material in which soluble trace ele-
ments are chemically bound such that their availability to subsequent
leaching is minimal or nonexistent. Chemical fixation converts a typi-
cally thixotropic sludge into a material that resembles either concrete,
clay, or soil, depending on the particular commercial processing used.
These materials are reportedly made suitable for landfill or structural
fill depending on the process used. In addition, a chemically fixed
sludge offers certain cost and convenience advantages for transport-
ing by truck, rail, or barge.
An additional property of sludge chemical fixation gained
by some methods is the conversion of the sludge to a material having
very low permeability. By combining the reduction of soluble compo-
nents with the reduction of permeability gained by chemical fixation, a
total reduction of potentially toxic elements available to the environ-
ment of 10,000 times or more may be realized.
An example of the degree of reduction attainable in the
soluble trace elements is illustrated by the results from a leaching
experiment conducted in September 1973 on a chemically fixed sludge.
Table 1-3 presents experimental data comparing the concentrations of
the trace elements in leachate from the fixed sludge against the origi-
nal TVA Shawnee Power Plant raw limestone sludge. Further work is
under way to refine the values of the concentration of constituents in
the leachate and to relate those values to corresponding values that
1-21
-------
Table 1-3. COMPARISON OF TRACE ELEMENT ANALYSES
BETWEEN RAW SLUDGE AND LEACHATE
FROM THAT SLUDGE AFTER CHEMICAL
CONDITIONING BY FIXATION (REF. 1-1)
(parts/million)
Constituents
Arsenic (As)
Cadmium (Cd)
Chlorides
Chromium (Cr) (total)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Mercury (Hg)
Nickel (Ni)
Zinc (Zn)
Phenol (C6H5OH)
Cyanide (CN~)
Sulfate (SO~)
TVA Shawnee
TCA limestone
raw sludge
2.2
0.30
2000
2.8
1.5
120
26
<0. 10
3.5
16
<0.25
<0. 10
> 10, 000
Leachate water from
conditioned sludge
<0. 10
<0. 10
64.0
<0.25
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
400
1-22
-------
define concentrations in the sludge leachate that has not been
chemically fixed.
An alternative method of sludge conditioning for disposal
might employ drying of the sludge so that a solid waste material is dis-
posed of. A major difficulty with dried sludge disposal is based on the
capacity of sludge to reabsorb water; thus, disposal by fill and bank
techniques may be necessary. In this case, and depending upon both
the physical effects and the potential for polluting the environment, an
impervious clay cover may be necessary to prevent reabsorption of
rain water and the dissolution of trace elements into leachate or run-
off waters.
In certain geological areas, conversion of sulfur waste
to commercial products may be economically feasible. Technology
exists to convert and use power plant sludge for a road-base material
or as structural aggregate. In addition, production of structural prod-
ucts (e.g., brick or block) is possible, or these wastes may be used
as feed for cement clinker production. The latter is a prime consider-
ation because the sludge can provide the lime originating from the sor-
bent and the agrillaceous components for cement originating from the
fly ash. However, these sintering processes will require a scrubbing
system for sulfur removal.
An additional technique for reducing or eliminating the
pollution potential of power plant sludge would use nonchemical additives
such as industrial waste materials or soils. Soils provide a mechanism
for dewatering the sludge, and if they contain clay, provide an ion ex-
change capacitance that may reduce or eliminate the availability of
toxic elements to subsequent leaching waters.
Except for preliminary analyses of chemical fixation,
the techniques discussed herein have not been evaluated relative to
their environmental acceptability or their cost effectiveness.
1-23
-------
1.2.9 Disposal Cost Estimates
1. 2.9. 1 General
Disposal cost estimates were made for each of the two
most prevalent disposal methods: ponding and landfill using chemical
fixation. Considerable information was provided by various sources;
however, for each method the cost data are widely variant. As a
result, the disposal costs are given in wide ranges of values consistent
with appropriate qualifications based on the many variable parameters
attendant to either disposal method. Although refinements are expected
during succeeding disposal cost studies in this program, the disposal
cost will always be expressed as a range of values, except when applied
to a specific disposal operation. This section summarizes this analysis
and includes significant disposal costs and appropriate rationale.
1. 2. 9. 2 Chemical Fixation Disposal Costs
The disposal costs by chemical fixation are dependent
upon many factors: the fixation process and the contractor operating
efficiency; sludge characteristics including water, ash, and chemical
content; disposal site physical characteristics and distance from power
plant; sludge transport method; disposal land costs and ownership;
residual value of disposal site; and environmental monitoring. Addit-
ionally, the costs depend upon whether the power plant uses a disposal
contractor or does the work itself. To determine these costs, data
were obtained from personal communications, visits, published techni-
cal papers, brochures, and testimony from the National Power Hearings
of October and November, 1973. Sources of these data were: power
companies - Commonwealth Edison Company and Duquesne Light Com-
pany; chemical fixation companies - Chemfix, Dravo Corporation, and
International Utilities Conversion Systems, Inc.; and the EPA Control Sys-
tems Laboratory. Disposal costs quoted by the power companies and fixa-
tion companies are listed in Table 1-4.
1-24
-------
Table 1-4. SLUDGE FIXATION COSTING ESTIMATES
All values are condition and site dependent
Source
Dollars/ton,
50% solids
Remarks
Commonwealth Edison
Company, Will
County Station
Duquesne Light
Company, Phillips
Station
International Utilities
Conversion
Systems, Inc.
Chemfix
Dravo Corporation
5.91
8.55
5.25
10.00
5.00
7.25
1.50-2.50
-5.00
1.50-3.00
On-site disposal -- vendor quote
Current estimate
Best experience
Worst experience
Target*
Total disposal
On-site disposal
On-site disposal
Total cost to customer; includes
pumping to 10 mi
Company operation - on-site disposal; excludes capital costs
These values, equated to sludges that are 50 percent solids, range from
$1. 50 to $10. 00/ton. All relevant factors pertaining to the values given
are not available; however, based on the data given, it appears that
except for extreme cases (e.g. , development or demonstration sites),
the general range of costs is approximately $2. 50 - $5.00/ton of sludge
on a 50 percent solids basis. Some additional costs may be incurred
for topsoil and/or seeding after the disposal site is filled.
1-25
-------
1.2.9.3 Ponding Disposal Costs
Ponding costs vary considerably for many of the reasons
given for fixation and for others quite different. For example, in
addition to the effects of sludge composition, transport, disposal site
characteristics and distance from power plant, land costs and owner-
ship, and environmental monitoring, there are effects such as type of
liner, liner delivery distance, site construction rates, dike height,
and pond capacity constructed within a given period. Based on data
provided by liner suppliers, ponding contractors, power companies,
and mining companies, cost estimates were made of ponding disposal
on a 30-year average basis. These costs (Figure 1-3) are given for
ponds constructed with both low and high priced liners and for various
land costs, and they indicate that on the basis of 30-year averages, the
costs should be in the range of $2.00 to $3.00/ton of sludge (50 per-
cent solids). Liner protection is limited by the liner life expectancy;
therefore, if the disposal site is to be usable land after the pond is
filled, it will have to be partially dewatered, protected against rewa-
tering, and landscaped. Practical technologies to account for perma-
nent environmental protection or land reuse have not been developed;
therefore, costs for these factors are not included.
1.2.9.4 Cost Comparisons - Fixation Versus Ponding
It is apparent that the costs of disposal by fixation or
ponding are indefinite and highly variable. This is because sludge
disposal by fixation is an emerging industry with little actual practice
at this time and, although the use of lined ponds is an established
technique in some industries, there is little experience with power
plant sludge disposal by that method. Furthermore, currently there
is no long-term performance data for either method. Cost compar-
isons are made by observing the range of values available and making
rational comparisons in light of the variations in requirements and
1-26
-------
5.0
1 I I I
PVC Thickness:
Cost:
T
T
4.0
TOTAL COST
. INCLUDING
LAND (at
$1000 per acre)
SL 2.0
1.0
20 mil
$1.60 per sq yd Installed.
Values applicable to equivalent
cost liners (see Figure 1-2).
"Land values represent the
maximum range ($0 to $5000/
acre) that would probably be
paid for disposal site land.
LAND _
TOTAL COST
WITHOUT LAND0
TOTAL COST INCLUDI
(at $5000 per acre)a
LINER ONLY
INSTALLED
COST
7.0
6.0
5.0
us
I
(O
"B
f
t
8. 3.0
V)
8
2.0
1.0
' I ' 1 ' T
HYPALON Thickness: 30 mil
Cost: $3.25 per sq yd Installed.
Values applicable to equivalent
cost liners (see Figure 1-2).
°Land values represent the
maximum range ($0 to S5000/
acre) that would probably be -
paid for disposal site land.
TOTAL COST INCLUDING
LAND (at $5000 per acre)0
-TOTAL COST
INCLUDING
LAND (at
_ $1000 per acre
LINER ONLY
- INSTALLED COST
'-TOTAL COST
WITHOUT LAND0
TO CONVERT:
FROM
mil
sq yd
acres
ft
short tons
$ per short ton
TO
cm
sq m
sq m
m
metric tons
mills per kWh
MULTIPLY BY
0.00254
0. 8361
4046.8
0.3048
0.9072
0.225
J.
_L
10 20 30
DIKE HEIGHT, ft
40
50
10 20 30
DIKE HEIGHT, ft
40
50
Figure 1-3.
Sludge disposal costs -- ponding
(30-year average)
-------
potential disposal methods. It is believed that the most accurate
comparisons (Table 1-5) should be made on a current cost basis,
thereby eliminating conjecture as to future costing effects which vary
depending on the disposal method considered as well as variations in
the economy. The fixation costs are estimates quoted for current
operations. The current ponding costs are based on initially purchas-
ing all land and ancillary equipment needed for a 30-year operation and
constructing a pond capable of containing a 10-year sludge and ash
supply (50 percent solids). This comparison indicates that ponding
will cost approximately half that of disposal by chemical fixation.
Permanent environmental protection and land reclamation are additional
factors that do not appear to favor ponding costs.
1.2.9.5 Disposal Costs Related to Power Produced
The following example considers the cost of fixation/
disposal of all sludge and ash produced at a 1000 MW station using a
limestone scrubber. A total of 1. 44 million tons of 50 percent solid
sludge (including ash) is produced per year; it is assumed that the
output of the plant is 6.4 billion kWh per year, and that the coal has a
3 percent sulfur and 12 percent ash content. The annual cost of this
form of disposal would be 0. 56 to 1. 12 mills/kWh, using a disposal
cost of $2. 50 and $5. 00/ton, respectively. If a lime scrubber is
used, the disposal cost would be from 10 to 20 percent less, principally
because the tonnage would be reduced. Also, reductions in disposal costs
should be possible by reducing the wet tonnage volume by collecting the
fly ash upstream of the scrubber and by reducing the water content of
the sludge.
1. 2. 10 Water Quality and Solid Waste Disposal Criteria
The measure of what conditions constitute the environ-
mentally sound disposal of sludges is defined by authoritative water
1-28
-------
Table 1-5. DISPOSAL COST COMPARISONS -- SLUDGE INCLUDING ASH-
50 PERCENT SOLIDS
($ per short ton; 1973 dollars)
ro
SO
Disposal site suitable for reclamation.
Soil cover not included. Current price
quotes.
Fixation
Cost,
1.50
3. 00
5.00
7.25
Remarks
Lowest quote
Ideal conditions
Disposal site adjacent to plant
No land cost included
Maximum quote by two processors
Fly ash supplied by plant
Disposal site up to several miles
distance
Land cost included in one case
Quote by one processor
Disposal site up to 1 mile distance
Target cost for one processor
No land cost included
Total disposal cost quote by one
power company
Values applicable to equivalent cost liners.
Represents maximum that would probably
be paid for disposal site land.
First year costs shown. Annual capital
charge 26.5 percent first year. Ten-year
sludge production capacity pond. Thirty-
year land cost included - no residual value.
Future effort may be required for permanent
environmental protection or land reclamation.
Ponding
Cost, $
a
PVC liner, 20 mil thick
1.00 -
1. 50 -
Hypalon
1.40 -
1. 80 -
1.50
2.70
a
, 30 mil thick
2. 50
3.70
Remarks
Land cost at $1000/acre
Land cost at $5000/acreD
Land cost at $1000/acre
Land cost at $5000/acreb
To convert Multiply
from to by
short tons metric tons 0.9072
acres sq m 4046. 8
-------
quality standards and solid waste disposal regulations,* or by the
judgment of regulatory officials when standards are nonapplicable or
nonexistent. The procedure, therefore, in the development of this
task effort has been to gather the existing standards to determine what
qualities or conditions must be prevented or controlled, and to com-
pare the criteria specified therein with the characteristics of as many
sludges as possible, including the effects of the disposal method on
the environment. Also, regulatory officials have been contacted for
information on methods of standards application. The collection of
standards has produced documents from all states for which water
quality standards are available at this time (90 percent of all states).
Accordingly, solid waste regulations have been obtained from 20 per-
cent of the states. This collection of solid waste regulations is con-
sidered representative for an initial determination of status based
on information provided by the EPA NERC, Cincinnati. All told, the
water quality standards identify numerical criteria for the quality of
receiving interstate waters. These criteria when considered in terms
of regulations that may be applied to the qualities of sludges include
items such as heavy metals, toxic materials, total dissolved solids,
pH, and various compounds such as sulfates and chlorides.
Water quality criteria for surface waters vary among
the states, but for drinking water supplies, the states generally repeat
or refer directly to the U.S. Public Health Service (USPHS) Drinking
Water Standards - 1962 that specify concentration limits for chemical
substances in a water supply. This portion of the USPHS standards is
reproduced in Table 1-6. Also, some states have regulations concern-
ing the quality of ground water. For example, Illinois requires that
*
Water Quality Standards consist of four major components: (a) use
designations, (b) narrative and numerical criteria, (c) a plan of
implementation and enforcement and solid waste regulations that
define various types of waste materials with requirements for dis-
posal, and (d) an antidegradation statement.
1-30
-------
Table 1-6. EXCERPTS FROM UNITED STATES PUBLIC HEALTH
SERVICE DRINKING WATER STANDARDS - 1962
The following chemical substances should not be present in a
water supply in excess of the listed concentrations where, in the judg-
ment of the Reporting Agency and the Certifying Authority, other more
suitable supplies are or can be made available.
Substance Concentration (mg/liter)
Alkyl Benzene Sulfonate (ABS) 0. 5
Arsenic (As) 0. 01
Chloride (Cl) 250.0
Copper (Cu) 1. Q
Carbon Chloroform Extract (CCE) 0. 2
Cyanide (CN) 0. 01
Iron (Fe) 0. 3
Manganese (Mn) 0.05
Nitrate (NC>3) 45.0
Phenols 0.001
Sulfate (S04) 250.0
Total Dissolved Solids 500.0
Zinc (Zn) 5. Q
The presence of the following substances in excess of the con-
centrations listed shall constitute grounds for rejection of the supply.
Arsenic (As) 0. 05
Barium (Ba) 1. Q
Cadmium (Cd) 0.01
Chromium (Hexavalent) (Cr ) 0. 05
Cyanide (CN) 0. 2
Lead (Pb) 0.05
Selenium (Se) 0.01
Silver (Ag) 0. 05
1-31
-------
underground waters that are a present or potential source of water
for public or food processing supply shall meet the general and public
and food processing water supply standards. In general, other states,
which do not have a specific regulation concerning the quality of under-
ground water, apply stream or drinking water standards to the under-
ground water for lack of more definitive regulations. Finally, accord-
ing to the EPA, in all cases, stream dilution is not to be considered a
substitute for or an extension of a waste treatment facility.
For the regulation of solid waste disposal, standards
are much less specific than water quality criteria. Regulations
ordinarily limit the disposal of toxic, hazardous, or harmful substances
by requiring that those materials not be disposed of on the ground, or
underground without the express approval of a designated authority such
as the State Department of Health, the State Health Commissioner,
County Health Commissioner, or the State Department of Commerce.
This survey to date indicates that those offices, when judging the dis-
posal of sludges, base their judgment on sludge quality as related to
USPHS water quality criteria.
The limitations imposed on sludge disposal are further
intensified by the recent and potential passage of legislation. For
example, the Federal Water Pollution Control Act Amendments of
1972 essentially require the revision and reapproval of all state water
quality standards: to change applicability from interstate waters to
all waters including ground waters, to specifically prohibit or limit
direct discharges of pollutants to streams, to limit sub-surface dis-
posal, and to include Federal EPA-prescribed criteria for specific
toxic elements. Additionally, the federal drinking water standards
are being revised, and legislation is in process to develop new limita-
tions for the land disposal of solid waste.
Chemical analyses conducted in this program have
shown untreated sludge properties that make those tested unsuitable
1-32
-------
for direct discharge into streams. Because of the wide variations in
soil properties and a lack of understanding of the attenuation of harmful
or undesirable components in soils, it is believed that untreated sludge
disposal on the earth or in an underground cavity may not be allowed
because of the potential contamination of ground waters. The charac-
teristics or components of concern in the sludges that have been anar
lyzed so far are: total dissolved solids, sulfates, chlorides, arsenic,
mercury, lead, and selenium, and other materials of lesser concen-
trations. A typical trace metal analysis of a limestone sludge is com-
pared to water quality criteria in Table 1-7.
With current water quality standards and solid waste
management regulations that prohibit sludge disposal in water and that
are being interpreted to prohibit its disposal on land without safeguards,
and with new and pending legislation that is or will be more restrictive,
it is apparent that the sludges must be disposed of in such a manner as
to prevent direct discharge to streams. It appears that it will be neces-
sary to prevent or control leaching through the soil to ground or surface
waters.
1-33
-------
Table 1-7. SUMMARY SLUDGE LIQUOR METAL ANALYSIS
COMPARED TO WATER QUALITY CRITERIA
TVA Shawnee Power Station; TCA Limestone Sludge
(parts /million)3
Element
Clarifier underflow
liquor
Arsenic (As)
Beryllium (Be)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr) (total)
Copper (Cu)
Lead (Pb)
Magnesium (Mg)
Mercury (Hg)
Selenium (Se)
Zinc (Zn)
0. 2U
0.01
0.005
2500°
0.05
0. 05
O.lb
600C
0.06d
0.3b
0. 5
o
Equivalent to mg/liter
Exceeds USPHS Standards - 1962 (see Table 1-6)
°Total dissolved solids exceed USPHS Standards -
(see Table 1-6)
Exceeds some state standards
1962
1-34
-------
REFERENCES
1-1. Personal Communication, Chemfix, Division of Environmental
Sciences, Inc. , Pittsburgh, Pennsylvania (September 1973).
1-35
-------
-------
SECTION 2
CHEMICAL CHARACTERIZATION AND CRYSTALLINE
PHASE DETERMINATION
2. 1 SLUDGE SAMPLING
A set of samples representing the input and output
constituents of the TCA test scrubber at the Shawnee Power Station
in Paducah, Kentucky, was obtained on three occasions: 21 Decem-
ber 1972, 1 February 1973, and 11 July 1973. The sample set col-
lected on 21 December 1972 was incomplete and, therefore, was not
used. Samples were collected by TVA personnel under the direction
of Mr. J. B. Barkley and sent by air freight to The Aerospace Cor-
poration in polyethylene bottles. The Shawnee samples represent
sludge produced by scrubbing flue gas from eastern coal with a lime-
stone sorbent.
A single sample set of sludge constituents was collected
by Bechtel personnel from the TCA prototype scrubber at the Mohave
Power Station on 30 March 1973. This set did not include coal,"1" fly
ash, or bottom ash. The Mohave samples represent sludge produced
by scrubbing flue gas from western coal with a limestone sorbent.
^Analytical data reported for western coal and fly ash were obtained
from Reference 2-1; averages of two measurements were used.
2-1
-------
A description of the samples is given in Table 2-1,
2-2, and 2-3. Flow diagrams showing the sampling stations are
given in Figures 2-1 and 2-2.
2.2 ANALYTICAL EQUIPMENT AND PROCEDURES
Suitable aliquots were taken for analyses. Methods
employed were emission spectroscopy (designated ES in tables of
analytical results), spark source mass spectroscopy (SSMS) and
atomic absorption (AA) spectrophotometry. The Perkin-Elmer 303
atomic absorption spectrophotometer with graphite furnace atomiza-
tion was used for the high precision measurements. Liquid samples
were filtered through Whatman 40 filter paper for both ES and AA
analyses. Solid samples were reduced (when necessary) to -0. 5 mm
(-32 mesh), quartered, and dried at room temperature over CaSO.
desiccant for all analyses. All samples were stored in polyethylene
containers.
The AA test procedure consists of injecting the liquid
samples at full strength into the graphite furnace and comparing ab-
sorptions against standard solutions of reagent grade chemicals. For
a few analyses samples were diluted with distilled/deionized water to
obtain on-scale absorption readings, but whenever possible spectral
lines of lesser sensitivity were used when concentrations were high
enough to saturate primary absorption bands [e.g. , for magnesium
(Mg) and zinc (Zn)]. Solid samples were also atomized directly in
the graphite furnace, using a tantalum cup and insertion spoon. For
some solid samples, particularly limestone and fly ash, the solids
were digested in concentrated acids and the resultant solution was
analyzed as a liquid sample. Interferences from volatiles hampered
the analysis of certain samples, particularly bottom ash and coal, but
the use of a deuterium background corrector on subsequent analyses
is expected to reduce interference.
2-2
-------
Table 2-1. SLUDGE SAMPLES ACQUISITION, SHAWNEE
POWER STATION, 1 FEBRUARY 1973
Sample
Process water make-up
Scrubber effluent slurry,
retained as slurry
Scrubber effluent slurry,
separated after sampling
Liquid portion
Solids portion
TCA inlet fly ash
TCA outlet fly ash
Clarifier effluent
Bottom ash, Unit No. 10
Coal from scale, pulver-
ized and quartered
Limestone from feed belt,
composite sample
Sampling
stationa
7
2
2
4
3
1
6
Quantity
100 ml
4. 40 liter
100 ml
20 gm
3 gm
3 gm
22 liter
100 gm
100 gm
100 gm
Time of
sampling
0700
0700
0700
0930 - 1130
0930 - 1130
0700
0900
0730 - 0830
0735 - 0835
Operating conditions:
Bechtel Test Run No.
428-2A
429-2A
Gas flow rate
Time
420 cu m/min 0700 - 1030
700.8cum/min 1030-1130
Coal consumption to Boiler No. 10
Power produced
Total ash production
Bottom ash production
42. 5 mt/h av
102 MW av
6. 66 mt/h av
1. 33 mt/h approx
See Figure 2-1
mt/h is metric tons/hour
2-3
-------
Table 2-2. SLUDGE SAMPLES ACQUISITION, SHAWNEE
POWER STATION, 11 JULY 1973
Sample
Process water make-up
Scrubber effluent slurry,
retained as slurry
Scrubber effluent slurry,
separated after sampling
Liquid portion
Solids portion
TCA inlet fly ash
Clarifier effluent
Coal from Unit No. 10
bunker
Limestone from feed belt
Bottom ash from Unit
No. 10
Soil near limestone pile
Sampling
station3
7
2
2
4
1
6
Quantity,
liter
0. 55
4. 40
0. 55
0. 55
33 g
0. 55
1. 10
0. 55
2. 20
4. 40
Time of
sampling
0820
0845
0840
0730 - 0930
0855
During day
7-10-73
0830
0800
1000
Operating conditions:
Coal consumption to Boiler No. 10
Power produced
Total ash production
Bottom ash production
40 mt/h av
95. 6 MW av
6. 21 mt/h avb
1. 54 mt/h approx
See Figure 2-1
mt/h is metric tons/hour
2-4
-------
Table 2-3. SLUDGE SAMPLES ACQUISITION, MOHAVE
POWER STATION, 30 MARCH 1973
Sample
Scrubber input from holding tank
Scrubber effluent
Centrifuge discharge
Liquid portion
Solids filtered from liquid
portion
Solids portion
Make-up water
Lime stone
Sampling
station2
1
2
4
4
3
5
6
Quantity
1. 10 liter
4. 40 liter
1. 10 liter
1 gm
5 gm
1. 10 liter
907 gm
Operating conditions:
Limestone depletion tests
Gas flow rate: 35.4 cu m/min
Time of sampling - 1330 - 1430
See Figure 2-2
2-5
-------
TCA
SCRUBBER
FLUE
GAS
| LIMESTONE
^^^^^
©
r
SCRUBBER
EFFLUENT
HOLD TANK
u
MAKE-UP
WATER
(
* *
i i
CLARIFIER
PROCESS
WATER
HOLD
TANK
GAS STREAM
LIQUOR STREAM
(x) AEROSPACE SAMPLING STATION
VACUUM
FILTER
SOLIDS
RESLURRY
TANK
SETTLING POND
Figure 2-1. Process flow diagram for TCA system at the Shawnee Power Station
-------
MAKE-UP
WATER
TANK
LIMESTONE
HOLDING
TANK
STACK
FLUE
CAS
PRECIPI-
TATOR
AEROSPACE SAMPLING STATION
PRECIPITATE
FOR DISPOSAL
1
SCRUBBER
Figure 2-2. Process flow diagram for Mohave station limestone
scrubber pilot plant
For the Shawnee samples, the flow sheets in Section 2. 4
show that the scrubber effluent slurry is reported in two ways: sepa-
rated and retained. The separated slurry sample was filtered imme-
diately upon collecting the sample by the TVA personnel taking the
sample. By immediately separating the liquid and solid portion, in-
teraction between the two phases is arrested. The retained samples
were separated at the time of analysis, 8 months for the 1 February
1973 sample, and 3 months for the 11 July 1973 sample.
2-7
-------
In this and subsequent discussions, no distinctions are
made among the three analytical methods employed (ES, SSMS, and
AA). For purposes of comparison, the preferred method is AA be-
cause its greater sensitivity gives it more precision and higher accu-
racy. In most, if not all cases, when the AA analysis of some ele-
ments has low sensitivity, it is still greater than that obtained from
the other analytical methods.
The SSMS test procedure consisted of wrapping a nomi-
nal 100 mg sample in gold foil that is then sparked against a high pur-
ity gold counterelectrode in a CEC 21-110X mass spectrometer. The
data are collected on a photographic plate as a function of mass /charge
ratio and scanned on a microdensitometer. Quantitative values are
determined by integrating line densities and comparing these intensi-
ties against standards developed for each element. Trace elements
at concentrations less than 5 ppm atomic are not listed.
The ES test procedure uses a sample that is acidified
in sulfuric acid and then ashed. Liquid samples are evaporated to
dryness, and the remaining residue is analyzed. A nominal 20 mg
sample is packed into a spectrographic grade carbon sample holder
and sparked against a similar grade carbon electrode. The emission
spectra are recorded on photographic film and scanned on a micro-
densitometer. By comparison of line density with standards, a semi-
quantitative analysis can be obtained for each element.
2. 3 ANALYTICAL RESULTS
The analytical results of these analyses are presented
in tabular form in Appendix B.
2.4 ANALYSES AND EVALUATIONS
This section discusses the regional (eastern/western)
occurrence of those elements (As, Be, Cd, Cr, Cu, Hg, Pb, Se, and Zn)
chosen because of their potential toxicity (Ref. 2-2). The simplified
2=8
-------
flow sheets show the level of the toxic element at each sample point
and could be used as a basis for a materials balance if appropriate
rate data were available.
2. 4. 1 Arsenic
Coal is an important source of the arsenic (As) ob-
served in the system. No analyses are available for As in the coals
used, but concentrations of 10 ppm are typical for eastern coals
(Ref. 2-3) and a value of 3 ppm has been reported for western coal,
originating from the Black Mesa Range (Ref. 2-1). Make-up water
appears to be a significant source of As in the Mohave pilot unit.
Under the reducing conditions of coal formation, As, a sulfide-
forming chalcophile like most of the metals discussed here could
occur as the sulfide (e.g., arsenopyrite, FeAsS; realgar, AsS; and
orpiment, A&2S2). Alternatively, arsenic could be organic in origin
as a consequence of the takeup of As by plant tissue, and in its trans-
formation during coalification it could remain organically bound or
appear so by forming a sulfide on the molecular scale. In addition,
substitutions of As in other minerals also commonly occur. Very
high As content in the super-fines of fly ash and the identification of
As in the carbon particles of coal by ion microprobe analysis suggest
its origin in the organic component of coal. During combustion of
the coal, As compounds are converted to oxides and carried in the
flue gas as fine particulates. Minor amounts enter the circuit in
limestone and make-up water.
Minor build-up of As is evident in the Shawnee circuit
(Figure 2-3) from February to July; this possibly implies that the sat-
uration concentration has been reached. The concentration of As in
the Mohave liquors (Figure 2-4) reflects the concentration in make-up
water.
2-9
-------
NUMBERS WITHOUT PARENTHESES: SAMPLES TAKEN 1 FEBRUARY 1973
NUMBERS IN PARENTHESES: SAMPLES TAKEN II JULY 1973
COAL
BERYLLIUM DISTRIBUTION, ppm
CADMIUM DISTRIBUTION, ppm
1 0.2 10.21 1 L^ j CHROMIUM DISTRIBUTION, ppm
t
PARTICIPATES
TO STACK
1 oo 1
o a
C ' ° j
^_^_ , : CQPPC
: i isi :
1 1 0 TO BE
! 20 110)
|B is)
1
1 1
PARTICULATES FLUE CAS
IN FLUE CAS .
1 34 1341 1
» 14) ;
15 a
R DISTRIBUTION, ppm
DETERMINED
I
BOTTOM ASH
[ 30 (331 |
| 0.4 (0.4) |
!~ II 1.7, ~|
I II o |
LIMESTONE
1 ' » 1
; ° IQ.il ;
: 4 12) :
MAKE-UP WATER
| < 0.0005 (0.0012) |
< 0.0005 (< 0.0005)-
^< 0.001 [< 0.001^
| 0.012 10.0051 |
25 (IB) |
1 1
4
1
LIQUID
1
1 1 1
SEPARATED RETAINED SEPARATED
| 0.001 10.020) | | 0.015 10.028) | | a a |
; 0.0094 |0. 0072) ; ; 0.0314 10.0092) ; . 2 12) .
0.025 a . f~ 0.006 (0.017) 15 o
0.041 (0.0601 I 0.021 (0.0641 ; 14 o
1 1 1
1
PROCESS
^
CLARIFIER
1
LIQUID SOLID
1 0.012 10.026] | | I (18) |
0.0039 (0.0039) | ' !"" ~i5i 1
^0.015 o ^ L '* ° J
0.051 IO.OS2) 9 (18] |
1 1
: B o :
SOLID
1
RETAINED
I a a 1
4 |3) .
L ° "3' J
: o (20)
I
i
Figure 2-3. Interim status of data development--level of heavy
metals at each sample point of the Shawnee Power
Station (sheet 1 of 2)
2-10
-------
t
PARTICULATES |N*FI
TO STACK
COAL
1 1 NUMBERS IN PARENTHESES: SAMPLES TAIfEM 11 JULY 10T1
1 ~ W * 1 1 LEAD DISTRIBUTION, ppm
| 4 (191 J !" | ARSENIC DISTRIBUTION, pptn
I a TO BE DETERMINED
1 1 1
UE OA?' FLUE <>« BOTTOM ASH
1 ' * 1 1 * " 1 1 ' '" 1
LZEI'.IZD r~r
::zu r^"^r~i
: ' :.:'
CIZIZIl ill
noi . la
1 1
|
^
3CHUDDC
LIQUID SOLID
1 1 1 1
LIMESTONE SEPARATED RETAINED SEPARATED RETAINED
| 0 |1. S| | | 0.030 o ] | 0.026 0 ] 1 ° ° 1 1 ' Ml 1
HjT.IE^ SHE
H H r
. i in :
L' "' J L '
MAKE-UP WATER
| < 0.005 (< 0.005) 1
' < o. 01 (
-------
rnn . k FLME lCAS , T
1 1
LIQUID SOLID
| < 0.001 ] [ O.M
< 1.0 J j 0.05 | j 0.4
r~--i r ,,7, ~\ i~ -i
l__l l_ _J L_ _1
: M : : 0.20 j : 6 '
1 )
1
'
IFUGE
1 1
* 1 1 *
LIQUID SOLID LIQUID SOLID
1 < 0.001 1 1 0.07 0.05
| 0.01 j j 0.6 ! 0.4 j
L """' H "~ ' ] H '7 ~I]
.J!1*1."-., : n n« : : 10 : : m :
1 v v
i
II III
LIQUID SOLID LIQUID .3OLID DISPOSAL
1 0.009 1 0.06 1 1 < 0.001 1 1 0.05
[ 0.07 j L< ' ' 0.0" \ '.» j
r -o,3 n [; ... ] £ ,2S -, j- -j
: 0.2 : : M ; o.» : 30 j
l
L MESTONE 4 fc
BERYLLIUM DISTRIBUTION, n>
CADMIUM DISTRIBUTION, ppm
CHROMIUM DISTRIBUTION, ppm
COPPER DISTRIBUTION, ppm
TO BE DETERMINED'
Figure 2-4. Interim status of data development--level of heavy
metals at each sample point of the Mohave Power
Station on 30 March 1973 (sheet 1 of 2)
2-12
-------
""L ' FLY «H
1 1 «
1 1 1 1
H H tl M ~H
O.MS j
3 i [ |
1 I
LIQUID SOLID
1 < 0.005 1 1 0.4
, , , . ,
1 1 | 1
c" - j r n
i ° : ! ° i
: 0.038 1 j 19
1
MAKE-UI
WATER
0.6
0.2
m~\
_ J
( O.OOOS
0.21
I
*
LIQUID
I
SOLID
I
SOLID
0.12
0.0012
0.03
SOLID
» 1
. 3 .
1 1
1_ ° _l
: 5-> :
I » j
1
1
.- 1
0.021
il"
| "] LEAD DISTRIBUTION, ppm
I ' \ SELENIUM DISTRIBUTION, ppm
^ ~ ~ j ZINC OlSTRtBUTION. pon*
' '. MERCURY DISTRIBUTION, ppm
[" j ARiCNlC DISTRIBUTION, ppm
a TO BE DETERMINED
Figure 2-4. Interim status of data development level of heavy
metals at each sample point of the Mohave Power
Station on 30 March 1973 (sheet 2 of 2)
2-13
-------
Arsenic oxide, As^O.,, has both acid and base
properties. In the scrubber it would form a mixture of the three
complexes of arsenious acid, [H^AsO,], [HAsOl], and [AsOT]; the
proportions would depend on the pH. At high levels of Eh, or oxi-
dation potential, an even more soluble arsenic acid complex, [H,,AsO~],
would be formed, though this is unlikely in a sulfite liquor without
purposeful oxidation.
2. 4. 2 Beryllium
Beryllium (Be) is found in both coal and limestone.
The content of Be in eastern and western coals averages 1-2 ppm
(Ref. 2-1), and either coal or limestone could account for the small
amount of soluble Be in the liquors.
Beryllium is found in nature as the mineral beryl,
Be.jAl.,Si/O. Q» but the Be content of the Shawnee samples is so low
that it probably occurs in substitution for Al or Mg. Pending further
analyses, it is presumed to deposit in the pond. This is desirable as
a step in the removal process, but only if we assume that the pond
deposits are completely immobilized. All aspects of loss from the
pond that might render Be airborne must be carefully studied; these
include spillage and flood washouts, breaching of pond walls, and
especially deflation of dried-out deposits by wind action. Beryllium
identified in Shawnee and Mohave samples is noted in Figures 2-3
and 2-4.
2. 4. 3 Cadmium
The cadmium (Cd) analyses give little indication of its
source or path in the circuit (Figures 2-3 and 2-4). Cadmium in coals
averages less than a part per million (Ref. 2-4); however, the Cd con-
tent of the limestone is sufficient to produce the observed concentra-
tions. It is uncommon in nature; the sulfide CdS or greenockite is
2-14
-------
widely associated with sphalerite, ZnS, primarily in coals. Cadmium
is so close to calcium (Ca) in ionic radius and charge that it is prob-
ably introduced in the limestone as a Ca substitute. Both the carbon-
ate and oxide of Cd are substantially insoluble, and it appears in the
scrubber effluent solids for removal to the pond. Conclusions about
the movement of Cd should be deferred, however, until more anal-
yses are made.
2.4.4 Chromium
The substantial chromium (Cr) content of the Shawnee
and Mohave coals shows up at all stages of the scrubbing process
(Figures 2-3 and 2-4). Chromium is lithophile or oxide-forming in
nature; its important ore is chromite, FeCr,O,,, but it substitutes
+3
readily for Fe having practically the same ionic radius. This sub-
stitution probably accounts for its presence in a coal having an Fe con-
tent of 4500 ppm. Chromite may hydrolyze in the alkaline circuit to
the amorphous species Cr (OH)_, which is insoluble but difficult to
remove by clarification processes. This may be the form seen in
trace concentrations in the scrubber and clarifier liquids.
The presence of Pb in the circuit introduced the possi-
bility that at least a portion of the Cr may be immobilized in the pond
deposit as the highly insoluble mineral crocoite, PbCrCL. This would
require an oxidizing regime to convert Cr to the hexavalent form and
is not likely to occur unless strong oxidizing conditions were imposed.
2.4.5 Copper
Copper (Cu) introduced into the scrubber system from
both eastern and western coals approximates 15 ppm (Ref. 2-3), with
minor amounts entering in limestone and water. During coal forma-
tion it would form stable sulfides (e.g. , chalcocite, Cu2S, and chalco-
pyrite, CuFeS-) and oxidize in the furnace to the insoluble oxides
2-15
-------
cuprite, Cu?O, and tenorite, CuO. In this form, it would appear in
the scrubber and clarifier solids, and finally the pond deposits with
only trace amounts showing up in the various liquid phases.
The Cu content of the Shawnee liquid samples is fairly
uniform at around 0.05 ppm (Figure Z-3). The slight increase in Cu
from February to July is not considered significant. When the scrub-
ber underflow liquid separated at the time of sampling is compared
to that retained in contact with the solids, the latter runs lower in Cu
content for the February sample (with a corresponding increase in Cu
in the solids), but is unchanged for the July sample. The lower pH
seems to be associated with the loss of Cu from solution to solid, but
the mechanism is unclear and can only be referred to possible sorp-
tion on fine particles. Since copper hydroxide, Cu(OH)_, is quite
insoluble, the higher pH of the July slurry liquid (retained) could also
be expected to reduce the content of Cu in solution, particularly since
the separated sample of July slurry liquid was acidic. Both samples,
however, showed about the same content of Cu (0.06 ppm). Hence no
conclusions can be drawn about the possible effect of pH on the com-
pleteness of Cu separation in the circuit and in the pond. (See Fig-
ure 2-4 for Cu distribution in the Mohave sample.)
2.4.6 Mercury
Mercury (Hg) in eastern coals averages about 0. 2 ppm
and in western coals is about 0. 05 ppm (Ref. 2-3). The limestone
and make-up water also contribute some Hg to the system. The aver-
age Hg content of limestones is 0.04 ppm (Ref. 2-5); make-up water
contributes approximately 0.05 ppm. The coal, consequently, is
expected to be the major contributor of Hg to the scrubber system.
Cinnabar and metacinnabar, the rhombic and cubic
crystalline forms of HgS, are the only common Hg ores. In nature,
it associates with Cu and Pb, and particularly with Zn as sphalerite,
2-16
-------
ZnS. Concentration of Hg in plant tissue as an organic complex
probably preceded the coalification that produced the coal beds.
Mercury is reduced to the vapor of the metal in the
boiler and remains in that state until cooled in the scrubber. The
amount of vapor escaping from the stack depends on the efficiency
of the scrubbing process. The greater part should be trapped, dis-
solved as the mercurbus ion Hg , or adsorbed on particulates. Its
path can be traced through the circuit only when more complete anal-
yses are available. Mercurous carbonate, Hg^CO,, is nearly insol-
uble (0. 05 ppm), but Hg is solvated in the form of various ionic com-
plexes, which may account for the relatively high concentration seen
in the slurry liquid. The higher Hg concentration in the liquid re-
tained in contact with the solids is supporting evidence for the grad-
ual solution of Hg from a solid phase. Nothing can be concluded at
this time about the saturation level of Hg; future levels may be even
higher than those determined so far.
The situation in the pond is modified by the introduc-
tion of atmospheric O2 into the system. This will oxidize the Hg to
the mercuric stage, Hg , which forms more soluble salts than Hg+.
A basic mercuric carbonate, HgCO32HgO, forms in an alkaline cir-
cuit that is insoluble and should be retained in the pond deposits. See
Figures 2-3 and 2-4 for Hg distribution in Shawnee and Mohave
samples.
2.4.7 Lead
Lead (Pb) in eastern and western coals averages 5-10
ppm (Ref. 2-3). There are lesser amounts in limestone and make-up
water, but coal is considered the principal contributor. Its mineral
galena, PbS, is the most likely form; the trace amount in the lime-
stone may be present as cerussite, PbCCy Anglesite, PbSC- is
found in an oxidizing regime; the last two forms may be important
2-17
-------
in the TCA circuit itself. The combustion product litharge, PbO,
is slightly soluble as are the carbonate and sulfite species, hence
we see some Pb in the slurry and clarifier liquids, and there is evi-
dence that it is accumulating in the liquid, but these concentrations
are not yet considered a serious problem. The small difference be-
tween the lead contents of the separated and retained liquids indicates
that pH changes do not affect significant amounts of lead solubility.
Lead should be stabilized in the pond deposits as
PbCO3 or 2PbCO3-Pb(OH)2 (white lead) and PbSC>4. Precipitation
by chromate under oxidizing conditions has been discussed; this would
give the least soluble species of those mentioned. Other forms could
eventually be leached from the pond, possibly slowly enough to pre-
sent no hazard. Lead distribution in the Shawnee and Mohave sam-
ples is given in Figures 2-3 and 2-4.
2.4.8 Selenium
The selenium (Se) content of coals averages about 1 ppm
(Ref. 2-3); this is comparable to the selenium entering the system from
the Shawnee limestone (30 ppm) such that the latter is considered an
equal contributor to the selenium in the circuit. Like As, Se is am-
photeric and may substitute for sulfur in pyrrhotite and chalcopyrite.
This substitution may account for its state in coal and possibly in
limestone. However, its chemical similarity to arsenic suggests
that selenium may also exist in the coal as an organic specie. Anal-
ysis has not yet detected the small amounts of selenium in the coal,
but it is presumed that its origin is similar to that of As. Under
weakly oxidizing conditions it forms soluble selenious acid, H-SeO,;
this ionizes in two steps, forming SeOl and HSeO~ so that the solu-
bility is pH-controlled. The amount of Se in the sulfite liquors sug-
gests that precipitation or adsorption processes do not take place.
Selenites of Ca and Mg are relatively insoluble; this may be the form
2-18
-------
in which Se is removed to the pond deposits in the solids. How well
it is retained there is open to question, but its stability is at least
suggested by the agreement in Se content between the separated and
retained slurry liquids in the Shawnee samples. Selenium distribu-
tion in the Shawnee and Mohave samples is given in Figures 2-3 and
2-4.
2.4.9 Zinc
Zinc (Zn) found in coals ranges widely (western coals
tend to have lower Zn contents than eastern coals), but values between
10 and 100 ppm are typical (Ref. 2-3). Reported analyses range from
20 to 2000 ppm so that the measured value (180 ppm) from the Shawnee
coal lies well within this range. Nevertheless, it is likely that coal is
the principal source of the Zn in the scrubber systems. Sphalerite,
ZnS, is the most likely Zn mineral in an average coal. Smithsonite,
ZnCO,, and hemimorphite (calamine), Zn .Si-jO-OH- H?O, are of les-
ser importance as sources of Zn.
The oxide ZnO, the combustion product of ZnS, sub-
limates readily (a method used in the refining of Zn) and some may
escape the scrubbing action. Zinc oxide is soluble only to the extent
of about 1 ppm, and the amphoteric nature of Zn may account for the
concentrations seen in the sulfite liquors:
ZnO + [SOj] + H2O ^ ZnSO3 + 2[OH~]
The ZnSO_ is soluble to the degree of about 0. 15 per-
cent. Some precipitation of ZnCO- may occur to bring the level of
+2
Zn in the liquor down to the observed levels. If it were not for
carbonate formation, oxidation of the sulfite in the pond might pro-
duce the highly soluble zinc sulfate and result in rapid loss of zinc
by leaching. Zinc distribution in the Shawnee and Mohave samples
is given in Figures 2-3 and 2-4.
2-19
-------
2. 5 SOLUBILITY APPRAISAL OF POTENTIALLY
TOXIC ELEMENTS
To make an overall appraisal of the occurrence of toxic
elements in the TCA scrubbing facility at the Shawnee Power Station,
certain speculations must be made based on the data presented and the
known chemistry of the constituents. No absolute trend toward a
build-up of soluble toxic elements in the circuit can be confirmed on
the basis of partial analyses. Moreover, in making an assessment
the limitations that must be taken into consideration are: (a) samples
may be representative of local test conditions and not representative
of the system, (b) the high ionic strength of the system affects the
solubility of each component in an unknown manner, (c) the possibil-
ity of forming soluble complexes is great because of the variety of
ions present and the pH and Eh factors, and (d) precipitation of a
trace metal may be retarded because of the high ionic concentrations
and these elements might remain in a supersaturated state until scav-
enged or coprecipitated in a major crystalline phase.
Nevertheless, the stability of compounds produced by
interaction of the ions of toxic trace elements with the major ionic
species present in the slurry can be estimated, at least on a qualita-
tive basis. Compound stability is a major determinating factor con-
trolling the solubility of the various elemental species in the sludge.
The solubility or insolubility of a compound is a relative factor and in
a dynamic system relates not to how much dissolves but to how much
dissolves in a given time. All compounds will completely dissolve
given enough leach water and time. Whether these compounds are
subject to slow or fast leaching from pond deposits, and to what ex-
tent they may be affected by environmental conditions will determine
their potential toxicity. An environmentally sound disposal method
need not prevent the introduction of the elements into the environment,
but rather control their rate of entry such that environmental health
2-20
-------
hazards are avoided. Insight into whether toxic elements in the
form of oxides, hydroxides, carbonates, sulfites, and sulfates might
be sufficiently insoluble in a scrubber system is given in Table 2-4.
When compared with the analytical data presented in Section 2. 4,
these data of known chemical behavior will reveal whether the sys-
tem is sufficiently buffered with the necessary anions to keep them
adequately immobilized for environmentally safe disposal.
Beryllium should precipitate as the sulfate and pos-
sibly as the sulfite, but some unknown amount of soluble carbonate
complex should also form. The relatively low concentration of Be
in the liquor probably represents that fraction existing as the soluble
complex; the remainder is sulfate or sulfite. Once in the sulfate or
sulfite form, it should remain in pond deposits and not be available
to the environment in amounts that warrant environmental concern.
The elements Cd, Cu, Hg, and Pb form stable car-
bonates that will remain in pond deposits unless leached by acidic
water. Mercury and lead can form insoluble sulfite, and this is prob-
ably the principal form in which they exist as a precipitate. Eventu-
ally, with an increase in oxidation potential they will convert to sul-
fates and the Hg will be able to leach away. Lead sulfate is highly
stable and will not leach at a rate of environmental concern. In addi-
tion, Hg forms an insoluble mercurous chloride that when oxidized
will convert to the more soluble mercuric chloride. The high con-
centration of Hg in the scrubber liquors possibly reflects the soluble
potential for Hg either as a chloride or sulfate.
Cadmium and copper also form insoluble hydroxides,
and these salts will remain stable in a basic environment. The con-
centration of Cd and Cu in the scrubber liquors is sufficiently low
because both form stable carbonates and hydroxide. Their concen-
tration in an acidic environment could, however, pose a greater
toxic hazard.
2-21
-------
Table 2-4. RELATIVE SOLUBILITIES IN WEAKLY ALKALINE
AND REDUCING SOLUTIONS
Toxic
cations
Be2 +
Cd2 +
Cr2 +
Cu+
Hg+
Pb2 +
Zn2 +
Major anions
co3=
Soluble
Insoluble
a
Insoluble
Insoluble
Insoluble
Very slightly
soluble
OH"
Insoluble
Insoluble
soluble
Insoluble
Insoluble
Insoluble
Slightly
soluble
Insoluble
so3=
Slightly
a
Slightly
soluble
Insoluble
Insoluble
Slightly
soluble
S°4
Insoluble
Soluble
Insoluble
Not formed
in water
Slightly
soluble
Insoluble
Soluble
Major
cations
Ca2 +
Mg2+
Toxic anions
AsO3
Slightly
soluble
a
SeO~
Insoluble
Insoluble
Data to be determined
Sources: Refs. 2-6, 2-7, and 2-8
2-22
-------
Chromium forms a very stable hydroxide and sulfite
in a basic liquor, and its low concentration in the scrubber liquor
reflects its immobilization in the system.
Zinc has no highly insoluble salts under the conditions
of a scrubber circuit and would be hard to retain as a pond deposit for
long periods. The hydroxide has sufficient stability to prevent Zn
from accumulating to high concentrations, but insufficient stability to
immobilize the metal. The high concentrations of Zn in the scrubber
liquor reflect the relative instability of zinc compounds in the system.
The arsenite, AsO^, is difficult to purge from the sys-
tem. Its calcium salt is slightly soluble; the solubility of the magne-
sium salt is not known. It forms insoluble compounds with some of
the trace metals present in the circuit, but its removal probably de-
pends on the efficiency of being scavenged by CaSO,. Its relatively
high concentration in scrubber liquors is undoubtedly a consequence
of the relative instability of arsenite compounds in the system. Be-
cause of this instability, As is expected to accumulate in a recircu-
lating system.
Selenium is chemically similar to As but the selenites
of magnesium and calcium are much more stable than the arsenites.
The relatively lower Se content in the scrubber liquor reflects the
greater insolubility of the selenites. Selenium is not expected to pose
a health hazard in this form, but it may accumulate in a recirculation
system.
Among the metals analyzed, As is the only element for
which an insoluble compound can not form in the sludge liquors. In
spite of this fact, several elements exist at concentrations in excess
of that which might be predicted from known chemistry. One explana-
tion might be the formation of complexes; in some cases this is un-
doubtedly true. The more likely explanation is gained from the obser-
vation that those metals with the greatest observed solubility are also
2-23
-------
those whose more stable compounds are carbonates. In some respects
this observation is also true for elements that form stable hydroxides.
This observation suggests, therefore, that a deficiency in carbonate
and hydroxide may exist in the liquors relative to the concentrations
necessary to precipitate these heavy metals to these equilibrium
levels.
In summary, As, Hg, Pb and Se are sufficiently soluble
to be of environmental concern. In addition, Be and B may be of
concern, but their potential hazard is not clear at this time. The
compounds of Cd, Cu, and Cr, are sufficiently insoluble so as not to
be of concern at the present state of understanding. This evaluation
is based on the precept that liquor waters will not sufficiently change
oxidation potential or pH from that measured. A greater health hazard
is expected under conditions of high oxidation potential and lower pH,
but a quantitative assessment of this hazard cannot now be given.
In addition to the toxic heavy metals discussed, two
other highly soluble elements are found in sludge liquors that must
be considered. Boron was found in the Shawnee coal at 46 ppm--a
value considered typical for both eastern and western coal. Chlorine
in the Shawnee coal has been reported as 2000 ppm (Ref. 2-9), but its
measured value in this study was 280 ppm. The former value is more
consistent with other data. The chlorine content of eastern coals
varies from 100 to 5000 ppm with an overall average content of 2000
ppm (Ref. 2-10). Western coals are expected to have a lower chlo-
rine content, but an analysis for these coals has not been found in the
literature. Boron is primarily associated with the organic portion of
coal whereas chlorine usually originates as soluble salts.
Boron will enter the scrubber as the oxide, B-CL, and
will hydrolize to soluble boric acid, H.BO-. Chlorine enters the
scrubber as gaseous hydrogen chloride and is easily entrained in the
scrubber liquor as the chloride ion. Neither element forms insoluble
2-24
-------
compounds with any major component within the scrubber system.
As a consequence, these elements will build up in the liquors or if
allowed to reach subsoils will percolate to the water table. The con-
centration to which these elements can build up is that at which the
loss from the system through the liquor component in sludge will just
balance the system intake. At the Shawnee TCA scrubber, this value
reached 7000 ppm in the liquor in a system operating not fully closed-
loop. For many coals, this value could exceed 1 percent of the scrub-
ber liquor.
Although these elements are not specifically toxic to
man, they do pose problems of concern. Boron is toxic to many
forms of plant life, many of them are part of the human diet. Only
the gaseous borane is known to be toxic to man, but when assimilated
in organic matter, there is an uncertainty as to whether this form of
boron may be toxic to man or animal. Nevertheless, agricultural
lands exposed to boron by runoff, spillage, or other inadvertent mis-
hap may be poisoned for further agricultural use for many years.
Chloride ions are highly corrosive to metals; thus, the
high chloride build-up that could take place may severely shorten the
life of the scrubber and auxiliary parts. Besides the economic conse-
quence of corrosion the possibility exists of metal components from
the scrubber hardware entering the scrubber chemistry. Elements
such as manganese, cobalt, chromium, nickel, vanadium, molybde-
num, and others are typically found in the steels used in power plant
construction. The solution of these elements in the liquor might
aggravate the hazards that originate in these sludge materials.
The high degree of uncertainty that exists with respect
to ionic species, solubilities, and solution rates of any of the elements
prevents evaluation of ionic concentration under conditions with varied
pH, Eh, or temperature. The occurrence of soluble complexes makes
2-25
-------
this evaluation even more difficult because complex chemistry is an
area that is just now being understood. Further evaluation of the toxic
hazard will require analyses under varied environmental conditions,
2.6 SOURCE OF POTENTIALLY TOXIC ELEMENTS
The primary source of trace elements found in scrub-
ber sludge is the fossil fuel--coal in these cases--but some signifi-
cant contribution of specific elements to the system enter from the
limestone and make-up water. Trace elements from the coal are the
consequence of combustion and enter the system either as a gas, in
particulates, or as adsorbed species on the particulates. Analyses
of trace elements as a function of the size of fly ash particulates have
indicated that certain elements are nonuniformly distributed. Other
trace elements found in the scrubber system are not found by analyses
among the particulates, and it is rationally presumed that their entry
into the system is through the flue gas. Some of the gaseous species
are physically adsorbed on the particulates, but their concentration in
this form cannot solely account for the quantity determined to be pres-
ent in the sludge.
Various methods were used in an attempt to reveal the
source of trace elements. Among the more successful was the ion
microprobe technique whereby the chemical analysis was determined
for individual particles. Particles of coal, sludge, and fly ash were
analyzed individually and in clusters. Lead and chromium were found
heavily concentrated in fly ash particles rich in iron. The inference
to be made by this observation is that these elements are associated
with iron either as a substitute ion or as a coprecipitated compound,
most probably as the sulfide. Beryllium and copper could not be de-
tected in individual particles of fly ash but were observed when a clus-
ter of particles was analyzed. Because they exist in the system at
lesser concentration, their correlation with more major elemental
2-26
-------
species could not be made and their origin in the system, therefore,
has not yet been determined.
Zinc was also found in the analysis of fly ash particles,
but its occurrence was dissimilar to that of lead and chromium even
though it exists at similarly high concentrations. The interpretation
of the data suggests that Zn is adsorbed on these particles, probably
as the oxide. Zinc oxide is the combustion product of zinc sulfide,
the most probable zinc compound in the coal, but some zinc may be
present as an organic fraction. The oxide sublimed during combus-
tion is believed to condense on the fly ash particles as the flue gases
cool. Furthermore, its presence as an adsorbed specimen gives it
ready accessibility that probably partially accounts for the relatively
high concentration of zinc in the liquor.
Arsenic and boron were found in the SSMS analysis of
fly ash but were not found by ion microprobe techniques of individual
particles. Particle cluster analyses by ion microprobe indicated
their presence, but specific correlation was not made. It was noted,
however, that concentration of these elements in the fine dust col-
lected downstream of the demister was greater than in the inlet par-
ticles to the scrubber. Since the fines in the fly ash particulate dis-
tribution are primarily the ash content of the organic fraction of the
coal rather than the mineral content, this distribution implies that B
and As originate as organic species. Ion microprobe analysis of coal
particles supported the association of these elements with the organic
content rather than with the inorganic content of coal. Electron dif-
fraction analysis of coal particles rich in organic content has revealed
crystalline inorganic matter in particle sizes as small as 0.01 and as
large as 1 micron. However, since neither element was observed in
individually large mineral particles of raw coal, it is concluded that
B and As originate within the organic portion. Selenium, although
not detected by any of these techniques, is believed to originate also
2-27
-------
in the organic portion of coal because of its strong chemical
similarity to arsenic.
Cadmium and mercury are chemically similar to zinc,
and much of their origination in the coal is in association with Zn,
especially Cd. The combustion product for both Cd and Hg is the
oxide, but the oxide of Hg is unstable at the temperature to which the
flue gas is cooled. The stability of the oxide of Cd lies between that
of Zn and Hg and may enter the scrubber as either the metal or oxide.
In either case, these metals enter the system as vapors in the flue
gas and become entrained in the scrubber liquors possibly with the
help of the carbonate and chloride ion.
Chlorine enters the scrubber as gaseous hydrogen
chloride in the flue gas. This gas is easily and efficiently scrubbed
by the liquor, and contributes to the source of hydrogen ions and
chloride ions.
In summary, the elements Be, Cr, Cu, and Pb enter
the system as particulates of fly ash; As, Se, and B also enter the
system as particulates, but they are more heavily distributed in the
fines and superfines. Cadmium, chlorine, mercury and zinc are
carried in the flue gas either as metal vapors, oxide vapor or as gas.
Possibly because of their gaseous dispersion, those elements carried
in the flue gas appear to be efficiently scrubbed by the liquors.
2.7 TEST STATUS AND PLANS
Sample sets from Shawnee (2 sets) and Mohave have
been analyzed by various chemical techniques. Since these analyses
are not yet complete, full chemical characterization is not now avail-
able; however, the data to date indicate that several toxic trace ele-
ments are or can be sufficiently soluble to cause environmental con-
cern in the handling and disposal of power plant sludges. The data
further suggest that a greater potential health hazard may exist under
conditions of greater oxidation potential and/or lower pH.
2-28
-------
Two additional sample sets from Shawnee will be
obtained as well as a set from a lime scrubber system and one from
a double alkali system. In addition, analyses will be conducted on
samples exposed to simulated environmental conditions of high Eh and
low pH, and on sludges chemically conditioned by several different
processes.
2-29
-------
REFERENCES
2-1. V. E. Swanson, Southwest Energy Study Coal Resources
Work Group, Part II, U.S. Department of Interior, Geo-
logical Survey, Denver, Colorado (January 1972).
2-2. Federal Register, Vol. 37, No. 234 (5 December 1972).
2-3. E. M. Magee, H. J. Hall, and G. M. Varga, Jr. , Potential
Pollutants in Fossil Fuels, EPA-R2-73-249, EPA Contract
68-02-0629 (June 1973).
2-4. T. Kessler, A. G. Sharkey, Jr. , and R. A. Friedel, Analysis
of Trace Elements in Coal by Spark-Source Mass Spectrome-
try, 7714, U.S. Department of Interior, Bureau of Mines,
Department of Investigation (1973).
2-5. I. R. Jonasson and R. W. Boyle, "Geochemistry of Mercury,"
Proceedings of the Process Society of Canada Symposium,
Mercury in Man's Environment, Ottawa, Canada (15 February
1971).
2-6. L. G. Sillen, "Stability of Metal-ion Complexes, Section I:
Inorganic Liquors," Special Publication, The Chemical Soci-
ety, London (17 November 1964).
2-7. W. F. Linke, Solubilities, D. Van Nostrand, Princeton,
New Jersey (1958).
2-8. Handbook of Chemistry and Physics, 38th ed. , Chemical
Rubber Publishing Company, Cleveland, Ohio (1956).
2-9. Personal Communication, J. B. Barkley, Chief Chemist,
Shawnee Power Station, Paducah, Kentucky.
2-10. Bureau of Mines Report, WO 7260 (May 1969).
2-30
-------
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SECTION 3
TOXICITY DETERMINATION
3. 1 INTRODUCTION
The determination of heavy element toxicity is dependent
upon observed physiological effects resulting from either carefully con-
trolled experiments or from an environmental catastrophe of epidemic
proportions. Clinical experiments rarely if ever precede the observed
consequence of illness and death that often results from acute exposure
to specific element intoxication. Moreover, health hazards from clini-
cal testing preclude these experiments so that the relationship between
exposure and the effects on human beings is most often evaluated from
the effect on animals. Thus, the resulting threshold or exposure limits
for humans are not always established with the certainty that may be
desired. The role of trace elements in man's biological processes is
only now beginning to be understood: many elements toxic to man in
relatively high concentrations are essential to his health in trace
quantities.
Nine elements found in nature in trace quantities (chro-
mium, cobalt, copper, iodine, iron, manganese, molybdenum, sele-
nium, and zinc) are essential to man's life or health; all are probably
3-1
-------
important catalysts for differing biological functions. In addition,
vanadium, nickel, fluorine, and arsenic are suspected of having a
useful biological function. Other elements, which are now consid-
ered inert, are found in human tissue and may perform useful roles
in the body, but the study of their biological activity has not been
undertaken. Cadmium, mercury and lead have no known biological
function and can act synergistically with other substances to increase
toxicity. Once in the human system, their toxic effects are cumula-
tive and are harmful to the degree that the dosages and resultant con-
centrations approach a lethal threshold. Even those trace elements
having proven biological function, when ingested at high concentra-
tions, can produce disease either by their accumulative effect or by
inhibition of natural functions.
From the two known accumulative diseases, hepatolen-
ticular degeneration from copper and idiopathic hemochromatosis from
iron, accumulative diseases are suspected for other essential cations --
chromium, manganese, cobalt, and possibly zinc and vanadium. The
medical profession has long recognized that all essential trace ele-
ments are toxic in excess. If it were not for homeostatic mechanisms
that reject excesses and conserve deficiencies, man would have to
regulate his intake voluntarily. For elements such as cadmium, lead,
and mercury to which man has experienced only recent exposure, it is
unlikely that adequate homeostatic mechanisms have developed. In
these cases trace elements are absorbed, accumulated, and eventu-
ally they lead to the development of disease. Cadmium represents
one of the more serious toxic elements because it causes kidney and
liver dysfunction, and it also interferes with the natural function of
zinc leading to arterial hypertension and toxemia of pregnancy.
In making an assessment of the toxicity created by
stack-gas scrubber sludge, a literature search was conducted to
determine the toxic limits of the trace elements present in fossil
3-2
-------
fuels and limestone. Appendix F provides a short review for some
of these elements; this review is continuing.
3.2 TOXICITY ASSESSMENT
The primary potential hazards to water quality that
may exist from power plant sludge arise from the solubility of arse-
nic and mercury. In addition, lead and selenium may present prob-
lems under certain environmental conditions.
Mercury, of all the potentially hazardous elements,
poses the most serious health problem. It is not found in coals at
high concentrations, but it is apparently efficiently scrubbed from
the flue gases. Although it can form insoluble compounds, the anal-
ysis of mercury suggests that these are not easily formed. Mercury,
when exposed to anaerobic aquatic environments, will easily and
readily methylate, thereby becoming increasingly more hazardous.
The scrubbing of mercury from flue gases can reduce the overall
environmental load if this mercury can be contained within the sludge.
As a soluble component, mercury has the potential of being released
to the environment at concentrations in excess of limitations for
water quality.
Although the preliminary data suggest that selenium
may be building up in the recirculation liquors, it is typically found
in low concentration in coal. Therefore, it is expected to reach a
saturation equilibrium in the system at a level that does not pose a
health problem. Since selenium is a micronutrient, homeostatic
mechanisms within the human body will be able to eliminate surpluses
over those required for good health.
Arsenic is an element used by the human body, but its
availability in coal can be 10 to 100 times that of selenium. Although
arsenic and selenium both have similar chemistry, arsenite's greater
solubility and its higher concentration poses a more serious problem.
3-3
-------
The full measure of this problem is not apparent in these preliminary
results.
Lead is an element much like mercury in that it serves
no useful purpose in the body and accumulates in the liver and kidneys.
Lead can pose a serious health hazard if consumed in high concentra-
tions, and it has appeared in some liquors at concentrations that
exceed drinking water criteria. However, lead forms relatively
insoluble compounds with many of the anions in the scrubber system
and is expected to be controlled by them under most scrubber
operating conditions.
For each of the elements discussed, the analyses on
which these evaluations were based are preliminary and subject to
change. Thus, these assessments must also be considered as tenta-
tive and subject to further evaluation.
3.3 ANALYSES AND EVALUATION
It is not yet possible to determine unequivocally whether
stack-gas sludge poses a health problem. Certainly, situations can be
presented whereby sludge can be a health hazard. Specifically, sludge
liquors contain concentrations of dissolved salts that are very high re-
lative to Public Health Department drinking water standards. It is
herein presumed that the liquors will be managed to prevent their
being directly intermingled with drinking water supplies. Hence, it
is one of the study objectives to define minimum disposal technology
that will prevent these sludges from becoming a health hazard. It
will become easier to define those conditions wherein the sludge does
not pose a health hazard rather than where it does.
Since reasonable precautions undoubtedly will be under-
taken to ensure these sludges are not introduced directly into public
waterways, access to the environment by more indirect means are
being considered. Examples might be through the percolation of
3-4
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leachate through the disposal site subsoils to reach the water table
and thereby enter a river or wells, or by pond overflows or pipeline
ruptures that permit liquors to enter a watercourse or poison agri-
cultural lands. The inadvertent access to the environment might be
the most dangerous situation because it might be detected only after
health problems are noted among the affected populous. It is the in-
tent of this study, therefore, to identify environmentally safe disposal
technology and the potential hazard created by the alternative sulfur
dioxide scrubbing processes.
Whereas sludge liquors may contain dissolved heavy
metal contents posing specific toxic hazards, the liquors also contain
soluble components that when ingested will render them noxious.
Specifically, high chloride contents will make them salty, sulfates
have a purgative effect, and carbonates give rise to gas generation.
In addition, many dissolved cations (calcium, magnesium, boron,
etc.) although not harmful to humans, are noxious when consumed in
high concentrations. Liquors are, therefore, not acceptable dis-
charges when they can enter a drinking water supply. The alterna-
tives are to allow precolation to the water table or provide for com-
plete containment. Defining the extent and safety of these alterna-
tives is essential to this study.
The presence of sulfate, sulfite, carbonate, chloride,
and hydroxide ions in the sludge liquors provides a high probability
that insoluble compounds will form with most toxic heavy metals
thereby reducing their availability to the environment, even under
inadvertent situations. The toxic problem now appears to be primarily
associated with arsenic and mercury because their chemistry includes
some soluble compounds in scrubber liquors. This task is continuing
so that determinations can be made of the full extent of this potential
health hazard and the potential toxicity of other elements.
3-5
-------
3.4 STATUS AND PLANS
Specific attention will be addressed to a build up in
liquor concentrations of arsenic and mercury in the recirculation
system of the Shawnee Power Station TCA scrubber system. In
addition, other elements will be monitored either to determine their
toxic potential or to provide insight into the scrubbing operation. An
explanation of the system's chemistry with respect to the concentra-
tion of dissolved elements will be attempted relative to the operation
variables.
Samples obtained from other power plants will be ana-
lyzed and compared with the Shawnee data to determine the chemical
similarities and differences existing as a consequence of materials
and system design variables. The objective of this task will be
satisfied by identifying the toxic potential of power plant sludges and
the situations in which these conditions exist.
3-6
-------
-------
SECTION 4
DETOXIFICATION POTENTIAL
4. 1 TOXIC CONDITIONS CONSIDERED
The potential capability for detoxification is a function
of the element or groups of elements that pose the toxic hazard (Sec-
tion 3). From the observed and known chemistry of the important
toxic elements in power plant sludges the heavy elements that are
most likely to create a water quality hazard are arsenic, mercury,
zinc, and possibly lead and selenium. Arsenic and selenium are
expected to form soluble acid complexes in the scrubbing operation.
Although the data are still incomplete, the preliminary analysis sug-
gests, at least in the case of selenium, that an insoluble phase forms
and immobilizes the heavy element. Whether a similar precipitate
also takes place with arsenic is still uncertain. Mercury appears
principally as the relatively insoluble mercurous chloride that is sta-
ble in the liquor at low oxidation potential, but becomes unstable at
high oxidation potential relative to the more soluble mercuric chloride.
Zinc is relatively insoluble as hydroxides, but the concentration of
hydroxide ions is low for the limestone scrubbing system. Lead is
insoluble as the hydroxide and as the sulfate.
4-1
-------
4.2 POTENTIAL DETOXIFICATION METHODS
Since the toxicity hazard from a sludge will originate
primarily from the sludge liquors or leachate, detoxification methods
must consider conversion of toxic components from the liquid phase
to a solid, or by concentration in a smaller liquid volume that can be
disposed of by water treatment or chemical fixation (Section 6. 6). A
variety of detoxification methods is theoretically available for con-
sideration, but few of them are economically feasible. Because of
the large volume of water used in a scrubber, any water treatment
process (e.g., a lime water softening treatment combined with other
methods such as reverse osmosis, flash distillation, or electrodi-
alyses is possible) must be applied to a side stream. However, the
cost of these treatment processes would be prohibitive in most cases.
Except for those situations where the treatment of a side stream may
be necessary to control and/or reduce chloride content to prevent
corrosion, alternative detoxification methods such as chemical fix-
ation of sludges would be more economical. Other methods might
include ion exchange, oxidation, pH change, thermal decomposition,
etc.
4.3 ASSESSMENT OF POTENTIAL DETOXIFICATION
The potential capability for detoxification of a sludge
is a function of the element or group of elements that pose a potential
toxic hazard. The elements identified in the limestone system as
having the capability most likely to create a toxic hazard are arsenic
and mercury and possibly lead and selenium. Since the potential toxic
hazard from a sludge will originate primarily from the sludge liquors,
leachate, or runoff, detoxification methods must consider conversion
of the potentially toxic components from the liquid phase to a solid,
or by concentration in a smaller liquid volume that can then be dis-
posed of by other means.
4-2
-------
The most technically advanced sludge detoxification
method is the chemical fixation process that converts sludge from a
highly water-retentive material to one that has properties suitable
for landfill or structural fill. In this conversion process, soluble
components are reported^to be chemically combined, and thereby
restricted in their availability to the environment.
The concentrations of the most soluble of the poten-
tially toxic elements in the limestone scrubber liquors may be reduced
by a chemical treatment or system modifications that increase pH
and/or retard oxidation within the scrubber system.
Among the more feasible detoxification schemes is a
water treatment of a liquor side stream in which chemical precipita-
tion (lime softening) may precede a secondary water treatment method.
Among the possible secondary treatments are: reverse osmosis,
flash distillation, electrodialysis, and ion exchange. For any of these
secondary treatment techniques to be effective, a reduction in total
dissolved solids must precede their use. These processes are rela-
tively costly; they might be considered cost effective in only rare
circumstances. However, since some of these water treatment tech-
niques will also reduce the chloride concentration in scrubber liquors,
savings will be realized by their use in corrosion avoidance of major
hardware.
A brine of very high dissolved solids content is a by-
product in some of these water treatment processes. This brine can
be disposed of by chemical fixation processes or by evaporation.
The relative costs of these various processes have not
yet been determined.
4.4 STATUS AND PLANS
The most probable potentially toxic elements have been
identified, and several alternative detoxification methods have been
4-3
-------
given cursory consideration. The element's detailed chemistry will
be defined further, and the alternative detoxification methods will be
considered further. In addition, detoxification techniques for other
elements that appear to pose a toxic hazard will be assessed when the
extent of their hazard has been identified.
4-4
-------
-------
SECTION 5
PHYSICAL PROPERTIES DETERMINATION
5. 1 IDENTIFICATION AND DESCRIPTION OF
SAMPLES
A number of physical properties were determined from
the Shawnee and Mohave sludges to provide a more complete charac-
terization of their behavior as they may limit or restrict sludge dis-
posal, handling, and transportation techniques. The material used
from the Shawnee sludge was the solids content of the underflow from
the clarifier. This is the material that might be normally disposed of
in a pond or lagoon if a secondary dewatering process were not used.
The centrifuge cake was used from the Mohave sludge as it would have
been disposed of. In each case, tests were conducted to reveal spe-
cific behavioral characteristics that might limit disposal or handling
during disposal. Since, in each case, the information desired was not
necessarily the physical property but rather physical behavior as ap-
plied to disposal, tests were designed to reveal this behavior in the
most direct and expedient manner. Standard procedures were changed
without compromising test results whenever and wherever these
changes appeared to be desirable.
5-1
-------
5.2 PHYSICAL PROPERTY MEASUREMENTS
5.2.1 Bulk Density
Knowledge of the variation in bulk density of sludge as
a function of its solids content is important in estimating the volume
required to dispose of a certain quantity of sludge. Transportation
handling problems may be eased by moving sludge as a slurry, al-
though it may require a subsequent dewatering step. Bulk density/
solids content data are essential to evaluate the alternative methods
of sludge transport and disposal.
5.2.1.1 Physical Model
Equations based on the rule of mixtures may be em-
ployed to predict the relation of bulk density to solids content when
the true solid density and the dry packed bulk density are known.
When water is added to dry packed sludge, voids and interstices are
progressively filled and the density of the mixture increases until the
sludge is saturated. At this point, all excess volume between sludge
particles is filled with water, and the mixture is at its peak density.
Further addition of water dilutes the mixture and reduces its density.
The bulk density p of a sludge may be calculated as a
function of weight fraction solids content S , in terms of the bulk den-
sity of dry packed sludge pg, the true density of sludge particles p and
the density of water p . For a sludge with solids content less than
the saturation (peak density) value
P P
srw /c 4\
(5'1}
S +p (1 - S )
c Ks c
For a sludge containing less water than the saturation value
5-2
-------
PB
P=S~ (5-2)
Both density expressions coincide at the saturation value defined by
B
(5-3)
Values of pB and pg are the only measurements required to produce
the smooth curve of bulk density versus solids content.
5.2.1.2 Experimental Procedure
The bulk density of dry sludge and the true density of
sludge solids were determined experimentally to obtain the values
necessary to evaluate Eqs. (5-1), (5-2), and (5-3).
Bulk density was obtained by casting sludge into a
3 3
2. 54 cm (1 in. ) block mold, allowing it to air dry, and measuring
the geometrical volume and weight of the casting. This value cor-
responds to settled and dried packing obtained without mechanical
compaction.
True density of sludge solids was determined using an
air pycnometer for measuring the total volume of individual grains of
sludge in an oven-dried weighed sample. The air pycnometer oper-
ates on the principle of Boyle's law to measure the volume of air dis-
placed by the sample from a container of known dimensions.
Data points were also obtained to verify the predicted
relationship. Sludges of established water content were placed in pre-
weighed graduated cylinders for subsequent weight and volume deter-
minations. Dried sludge cakes were progressively re-wet, and the
weight and geometrical volumes were determined. Additional data
5-3
-------
points were determined from some of the dewatering study
measurements that could provide simultaneous bulk density/solids
content values.
5.2.1.3 Bulk Density Test Results
The true density of solids of the Shawnee sludge sam-
ple is 2.48 gm/cm . Packed dry Shawnee sludge solids have a bulk
3
density of 1. 20 gm/cm . The variation of bulk density versus solids
content as calculated is shown in Figure 5-1. The sludge-water mix-
3
ture attains a peak density of 1. 7 gm/cm at 70 percent solids. At this
point, all the solid particles remain packed together, with water
completely filling all the voids and interstices between particles.
Agreement is excellent with subsequently determined
bulk density/solids content values. Levels of solids content obtained
by different dewatering steps are also shown on the figure. Practical
dewatering methods do not remove sufficient water to obtain maximum
bulk densities in this sludge.
The variation of bulk density with solids content for
Mohave sludge with a solids true density of 2. 53 gm/cm and a bulk
3
density of 1.46 gm/cm is shown in Figure 5-2. The saturation (peak)
3
density (1.87 gm/cm ) corresponds to slurry containing 78 percent
solids. Levels of dryness obtained by various dewatering methods on
Mohave sludges are also shown in this figure. In this sludge, maxi-
mum bulk densities can be obtained by dewatering.
5.2.2 Corrosion
The useful life of sludge handling machinery and piping
may be limited by corrosion. Bench scale tests were performed to
determine if any particularly corrosive behavior might be observed
in handling the Shawnee sludge.
5-4
-------
20 40 60 80
SOLIDS CONTENT, weight percent
100
Figure 5-1. Shawnee sludge bulk densities
5-5
-------
1.0
20 40 60 80
SOLIDS CONTENT, weight percent
100
Figure 5-2. Mohave sludge bulk densities
5-6
-------
5.2.2.1 Experimental Procedures
Test strips of 1100 aluminum and 1010 mild steel
were numbered, cleaned, and preweighed. The strips were mildly
etched in 0. 1 N solutions of HC1 for mild steel and 0. 1 N NaOH for
aluminum to remove residual oxide layers. The sliding sludge would
effect a similar oxide removal (polishing action) in sludge handling
systems.
A group of test strips was immersed in sludge for a
4-month period. At 1-month intervals, some test strips were re-
moved from the sludge, rinsed, dried, and weighed.
5.2.2.2 Corrosion Test Results
Aluminum samples showed only about 0.2 percent
weight loss over this period. Aluminum exhibited corrosion resis-
tance due to formation of an adhering protective oxide that was not
breached by action of any chemicals in Shawnee sludge. Localized
minor pitting, which was confined to small areas, undoubtedly pro-
ceeds at an impurity inclusion.
Mild steel samples were more generally attacked. Cor-
rosion products would act to cement sludge particles to the test strips
and, by this effect, weight gains to 26 percent were observed after
4 months. Earlier in the study, insufficient corrosion had taken place
to provide enough corrosion products to bind sludge particles, and a
minor weight loss was observed.
Attack of mild steel does not appear to be caused by
the chemical nature of the sludge. Exposure of test strips to sludge
liquor alone was equivalent to the exposure by total immersion in wet
sludge solids. Accelerated attack was observed, however, if a test
strip spanned a region of solids to liquor. This effect is due to an
oxygen concentration gradient between the area of sample exposed
to the liquor and the area immersed in the sludge solids. A similar
5-7
-------
reaction accounts for the rusting of nails in wood. Anodic reaction
proceeds in the oxygen-deficient sludge region dissolving iron, and
the iron salts eventually serve to bind sludge particles. Cathodic
reaction proceeds at the steel surface in the water region, and iron
rust as Fe(OH)_ precipitates there. This rust is nonadhering and
rinses from the steel strip prior to weighing.
Common iron rusts to destruction because its oxide is
nonadhering. No chemical acceleration of rusting was observed in
this study with Shawnee sludge relative to a control blank immersed
in water adjusted to the pH of the sludge liquor. However, a corro-
sion couple (formed by contact with both the highly anaerobic sludge
solids and liquor containing some dissolved oxygen) will lead to ac-
celerated corrosion of the portions in contact with the solids.
5.2.3 Viscosity
The viscosity of a fluid affects the steady-state power
requirements for pumping it. In addition, the rheological behavior of
a fluid must be appreciated if problems are to be avoided in handling
non-Newtonian fluids. Since the solids content of a sludge is the
parameter that may be most practically used to adjust its viscosity,
the viscous behavior of sludges was measured as a function of solids
content.
5. 2. 3. 1 Experimental Procedure
The measurements were performed at room tempera-
ture using a viscometer having a cylindrical sleeve immersed in the
fluid and rotated at 64 rpm, representing a shear rate of 7.9 cm/sec
(15.6 ft/min) at the surface of the 2. 4-cm-diameter (15/16 in. )
rotating sleeve.
Prior to measurement, the solids content of the sludge
was adjusted to the desired value, and the mixture was homogenized
by hand stirring. The measuring cylinder was immersed in the sludge
5-8
-------
and left undisturbed for 1 minute at which time the viscometer was
turned on and the initial (peak) viscosity was noted. As the viscom-
eter cylinder continued to turn, the measured viscosity (rotational
resistance) decreased. When the viscometer was turned off for a
short period (about 1/2 minute) and restarted, the viscometer read-
ing immediately returned to that value recorded just prior to being
turned off and not to the original higher value. If the viscometer was
turned off for longer times (typically in excess of 1 minute), the ini-
tial peak viscosity was again recorded.
5.2.3.2 Viscosity Test Results
The peak viscosity of the Shawnee sludge with water
content adjusted from 40 to 50 percent varied from 120 to 20 poise
as shown in Figure 5-3. For the stiffer (higher viscosity) suspen-
sions, the measured viscosity decreased within 1 minute to an equi-
librium value 40 percent less than the peak value. The measured
viscosity of the more fluid mixtures decreased only 20 percent in
1 minute. When the viscometer was turned off, the torque on the
rotor did not return to zero. This behavior is representative of a
Bingham solid in which a critical shear stress must be exceeded to
initiate flow.
Measurements were not extended to sludges with water
content outside the 40 - 50 percent range. Slurries with a water con-
tent greater than 50 percent would not remain homogenized long enough
to attain a measurement of viscosity because of a rapid settling of
particles. Values dropped to those approaching water as a function
of settling time and not as a function of the shear stresses created
by the viscometer cup. Stiffer suspensions of water content lower
than 40 percent would require the use of a different viscometer rotor
which, instead of a cylinder, uses a disc rotated about its normal
axis. The disc rotor broke free of the suspension too readily, and
5-9
-------
140
120
100
o
M
a so
>^
H
l/J
8 60
vt
>
40
20
C
\
\
Q
\
\
\
\
\
\
\
O^ PEAK VALUES
N /
x /
0 X /
N/
X N
X X
^ v.
«A x
2a*x X
7"-x X-Q
/ ^ ^^
/ ^-^ Xx
/ ^^^ °^
EQUILIBRIUM A^ ^x
VALUES ^^>s
A
A i 1 i i i i i i i i i 1 i
1 Y 40 50
WATER CONTENT, weight percent
Figure 5-3. Viscosity of Shawnee sludges
5-10
-------
erroneously low measurements were obtained. Attempts to correlate
viscosity measurements obtained by using the two rotors where their
ranges overlapped were unsuccessful because of this effect.
Fluids that exhibit a viscosity which decreases with
time after shear is initiated are called thixotropic. Fluids may ex-
hibit thixotropic behavior when intermolecular bonds are broken by
shearing forces, creating smaller, less intertwined molecular struc-
tures and allowing flow more easily past one another. Sludges, how-
ever, are two-phase mixtures of small clumps of particles (or dis-
crete particles) and water. The thixotropic behavior appears when
the two components of a homogeneous mixture are separated by shear
stresses, and the more fluid component (water) concentrates along
the shear boundary layer defined by the viscometer cup and sludge
interface.
Procedures used to measure the viscosity of Mohave
sludge slurries differ from those used on Shawnee sludge slurries in
one notable exception. The Mohave sludges are clay-like in that they
flocculate readily and are difficult to mix into a suspension because
they coalesce and settle rapidly. Mixing the sludges into a slurry
suspension requires scraping a small amount of sediment from the
bottom of the mixing containers and thoroughly stirring it into the
fluid phase. Then an additional scraping of sediment is dispersed,
and so on, until the entire mixture is in suspension. The viscometer
rotor is then introduced into the sludge and quickly (before the par-
ticles settle) the viscometer is turned on to obtain the peak reading.
Operationally, the chief difference is the time allowed for the vis-
cometer rotor to assimilate to the sludge--! minute for the Shawnee
sludge, 5 seconds for the Mohave sludge.
Viscosity values for Mohave sludges at several water
contents are shown in Figure 5-4. The difficulty in stirring stiff mix-
tures and their fast settling tendencies limited measurements to
5-11
-------
«JV
40
o>
V)
I 30
H
O ?0
U
v>
>
10
0
O
O
PEAK VALUES *
^^
\
EQUILIBRIUM H
VALUES \
\ \
\ t
\ v-
N A
^x
^\
A \ , , , | I
O
)
s
i
\
\
*\
S^\
i i
0 f30 35 40
WATER CONTENT, weight percent
Figure 5-4. Viscosity of Mohave sludges
viscosities less than 50 poise, whereas Shawnee sludge viscosities
were measured to values as high as 120 poise. Equilibrium values,
after stirring by the viscometer for 1 minute, are also shown on
Figure 5-4.
Curiously, the viscosity measured after 1 minute stir-
ring is subject to fluctuations. Occasionally, during long stirring
periods, the measured viscosity temporarily increased by as much
as 50 percent from the "equilibrium" value. This sporadic rheopectic
5-12
-------
behavior could overload a pumping system designed for the lower
equilibrium value. Fortunately, this effect is only found in the stif-
fer mixtures having less than 35 percent water content.
In contrast to the Shawnee sludges which showed a
gradual increase in viscosity as the water content of the sludges
varied from 50 to 40 weight percent, the Mohave sludges rapidly
become more viscous at water contents below 40 weight percent.
This would be expected due to the clay-like properties of the Mohave
sludges--enough water allows the material to slip readily, and slightly
less water allows the clay-like particles to bond together.
The high initial viscosity value represents more nearly
the "viscosity" of the sludge suspension. Continued turning of the
viscometer rotor draws lubricating water to the viscometer sludge
interface, reducing the apparent viscosity similar to the behavior
observed with Shawnee sludges.
5.2.4 Compaction Strength
Criteria for safe access to a pond by personnel or
equipment can be based on the compaction strength of the sludge.
Monitoring the mechanical stability of the sludge is facilitated if the
compaction strength can be determined by correlation with convenient
elementary measurements.
The parameter most significantly affecting the com-
paction strength of a given sludge is its water content; therefore,
measurements were made to correlate the variation of compaction
strength with water content of the sludges examined in this work.
In addition to establishing a basis for convenient compaction strength
monitoring, the determination of most physical properties parametric
in water content provides a common basis for comparison and
cross -correlation.
5-13
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5.2.4.1 Experimental Procedure
Compaction strength was measured by determining
the penetration resistance of a 0. 95-cm-diameter (3/8 in.) rod pushed
into the sludge at a rate of 1. 27 cm/min (1/2 in./min). An Instron
testing machine was used to determine load for these measurements .
The sludge was retained in a 3. 8-cm-diameter (1-1/2 in.) cylinder of
sufficient depth that edge and bottom effects were negligible. For the
penetration depths employed, buoyancy effects were insignificant.
Sludge was poured into the cylindrical container and
allowed to settle, excess water was siphoned or wicked off the top of
the settled sludge, and the sludge was allowed to dry to the desired
water content. Measurement of this value was determined by weight
loss after each test.
After the water content had been adjusted for each test
run, the test rod was brought into contact with the sludge, and pene-
tration was begun. After the rod had penetrated 0.6 cm, a constant
compressive resistance was attained which persisted as the rod sank
deeper into the sludge. Penetration depths to 2. 5 cm were employed
in these experiments. This procedure was repeated to obtain a set
of compaction strength values at several water contents for both the
Shawnee and Mohave sludges; these data are presented in Figure 5-5.
5.2.4.2 Compaction Strength Test Results
Sludge of low water content, capable of supporting loads
in excess of 30 psi, showed compaction behavior more like a restrained
solid--increasing penetration required increasing force. Under these
conditions, geometry and dimensions of the confining container become
significant. However, it was shown that load carrying capacities of
this magnitude occur when the strength is increasing rapidly with de-
creasing water content, and detailed correlation of strength and water
content is difficult and of little value.
5-14
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30
35 40
WATER CONTENT, weight percent
45
Figure 5-5. Sludge compaction strength
Compaction strength was measured for Shawnee sludges
of water content from 45 to 30 percent. At 45 percent water
content, the sludge can sustain virtually no load, while at 30 percent
water content, a load bearing capacity of 2. 1 - 2. 4 X 10 dyne/cm
(30 - 35 psi) exists. The variation of compaction strength with water
content for Shawnee sludge is shown in Figure 5-5. It is estimated
5-15
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that a person exerts approximately 2X10 dyne/cm (3 psi) while
standing. Support of this level by Shawnee sludge would be attained
at 39 percent water content.
At 30 percent water content, where the strength is
increasing rapidly, the sludge is just at its saturation point. (This
is the peak density point on the bulk density versus solids content
curve, Figure 5-1.) Removal of additional water reduces the lubri-
cation between sludge particles and accounts for the dramatic in-
crease in strength.
It is interesting to note that compaction strength and
viscosity measurements overlapped the water content range from
40 to 45 percent.
Safe access for personnel can probably be granted if
the water content is less than 35 percent, at which point a load bear-
ing capability of 5. 5 X 10 dyne/cm (8 psi) is expected. It should
be noted that this corresponds to the dryness obtained by vacuum
filtering--the most effective water removal process. Access to vehi-
cles could probably be granted when the water content was less than
30 percent. However, it should be noted that around 30 percent the
strength varies rapidly with water content.
Compaction strength measurements for the Mohave
sludge do not vary smoothly with water content. Instead, 35 percent
water content marks a sharp change in compaction strength (Fig-
ure 5-5); at that value, compaction strengths range from 2 to 20 X
5 2
10 dyne/cm (3 to 30 psi). Pressure from the penetrating plunger
squeezes water from the plastic clay-like sludge and packs sludge
particles firmly together.
Water content less than 35 percent can be attained with
Mohave sludges using any of the dewatering processes --settling, cen-
trifuging, or vacuum filtering. Consequently, if no free standing
5-16
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water is present, a pond of Mohave sludge is probably safe for
personnel and most equipment.
5.2.5 Pozzolanic Strength
The structural integrity and draining characteristics
of sludge used for land fill depend on the degree to which the sludge
particles fit and bind together. Pozzolanic reaction, if it were to
cement sludge particles together, would enhance the compressive
strength of packed dried sludge as a function of time. Pozzolanic
reaction is that reaction which takes place in the cure of concrete
when a pozzolan such as fly ash is added to the mix.
5.2.5.1 Experimental Procedure
To measure pozzolanic effects in sludge samples,
cylindrical test specimens were cast for evaluation by compressive
loading. Specimens 1.3 cm (1/2 in.) in diameter by 5 - 8 cm (2-3
in.) long were tested after curing for various periods after casting.
Initial "uncured" strength is measured after 5 days when the excess
moisture has been drained and the samples can be unmolded. Addi-
tional curing took place in a humid environment with samples being
removed for testing at 1-month intervals. The specimens were
tested on an Instron test machine using a cross-head speed of 8. 4 X
10 cm/sec (0.02 in./min).
5.2.5.2 Pozzolanic Strength Test Results
Shawnee sludge samples crushed under less than a
2. 3 kg (5 Ib) load, representing a negligible strength of 1. 8 X 10
2
dyne/cm (26 psi) at each consecutive test over four monthly intervals.
Mohave sludge samples showed reasonable strength of
12 X 10 dyne/cm (170 psi) for uncured, damp specimens. Test
specimens cured for longer periods and allowed to dry before testing
crumbled under a stress of only 7 X 10 dyne/cm (100 psi). This
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behavior has been interpreted as a function of water content and is
completely analogous to the strength characteristics expected of clay-
bonded fine aggregate.
Neither the Shawnee nor Mohave sludge examined in
this work shows any characteristics of pozzolanic reaction that would
lead to increased bonding between sludge particles and increased com-
pressive strength. It should be noted that the Mohave pilot scrubber
was downstream of electrostatic precipitators, while the Shawnee
scrubber was not. Consequently, the solids portion of the Shawnee
sludge contained fly ash (approximately 40 percent by weight). A
pozzolanic strength effect might be expected because of the fly ash
content; however, as noted previously, it did not appear after 4 months.
5.2.6 Drainability
Drainage characteristics of sludge are particularly
significant for proper pond design or in its use as a landfill by en-
vironmentally sound disposal techniques. Laboratory-scale experi-
ments were designed to provide information on the rate of water per-
meation through sludge beds as a function of the bed thickness and the
head of water over the bed. These data are suitable for extrapolation
to predict field conditions.
5.2.6.1 Experimental Procedure
The experiment was configured about a 3.8-cm-
diameter (1.5 in.) column of sludge established over four sheets of
Whatman 40 filter paper supported on a glass frit filter. This ar-
rangement provided support for the sludge, yet permitted water to
drain freely from the bottom of the column. The rate of permeation
of water through the filter paper/glass frit filter combination alone
exceeded by at least 100-fold the rate of permeation through sludge
columns. Sludge columns of Shawnee sludge with nominal heights of
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5, 12. 5, and 25 cm (2, 5, and 10 in.) were employed in this study.
Hydraulic heads to 2. 5 m (6 ft) were established over the sludge
columns. Water drained from the column was collected in a gradu-
ated cylinder from which the amount drained was recorded as a func-
tion of time. A head loss of 2 cm (3/4 in.) was typical for each run.
Some settling and tighter packing occurs as the water
drains through a freshly established column. A nonlinear draining
curve is obtained until the sludge settles to a more fully dense
position.
5.2.6.2 Drainability Test Results
Drainage rates at steady state are plotted in Figure 5-6
as a function of the height of water head over the sludge. As expected,
a short column of sludge poses less resistance than a tall column and
drains at a faster rate. When water is poured on top of damp, freely
drained sludge, water immediately begins to drip from the bottom of
the column. This suggests that the sludge acts as a wick. When ex-
cess water is supplied at the top, the water is immediately transmitted
through the column. When no head exists over the sludge, no water
will drain; only excess water drains.
An additional head of water inducing drainage appears
to be in the sludge itself. This hidden pressure is shown by the nega-
tive intercept on the pressure axis in Figure 5-6. If the height of the
sludge column were added to the pressure head, all lines would inter-
sect at the origin--zero drain rate at zero head. The supernatant
head, when corrected to an effective head by adding the height of the
sludge column, will give a sludge permeability (cm/sec) in terms of
(5-4)
[Head Recession Rate(-^2-)"|
Effective Head (m) J X Bed Hei8ht
-------
2.6
2.4
w
fc M
111
h 1.6
o
lii ] 9
O l'c
in
U
0.8
0.4
COLUMN HEIGHT
O 5 cm
O12.5 cm
D25 cm
1 2
SUPERNATANT HEAD, m
Figure 5-6. Drainability of Shawnee sludge
5-20
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For the 5, 12.5, and 25cm experimental columns, the sludge
permeability determined as above is 2.23, 2.27, and 2.31 X 10
cm/sec for each column, respectively. The permeation rate (head
recession rate) for a given pond of sludge would be given by mul-
tiplying this specific sludge permeability by the effective head height
(m) and dividing by the sludge bed thickness (m). The effective head
is, of course, the bed thickness plus the height of standing water.
When only a thin film of water covers the sludge, the
factors of bed thickness and effective head height are identical and
mutually cancel. This represents the wicking condition alone that
predicts that the rate of water transport by wicking is independent
of the bed thickness.
5.2.7 Water Retention
Minimizing land required as a disposal site and con-
ditioning the sludge for disposal will ultimately require dewatering
of sludge at some stage in handling; therefore, information on the
capability to dewater sludge by common techniques is necessary in
the assessment of sludge disposal problems.
5.2.7.1 Experimental Procedure
Dewatering of Shawnee and Mohave sludge was per-
formed by techniques of settling, centrifuging, and filtering. An
additional water content is also considered that was obtained by the
Shawnee "clarifier" stage and as a result of free draining.
Sludge-water slurry was settled in a graduated cylin-
der and the supernatant decanted, leaving sludge dewatered by settling.
Sludge was also dewatered using a laboratory centrifuge to settle the
sludge, after which the water was decanted. Water separated from
sludge using vacuum assisted filtering and Whatman 40 filter paper
produced a filter cake. A water aspirator was used as the vacuum
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source, and care was taken not to draw air through the dewatered
cake which would cause extra drying. Sludge freely drained in the
drainability experiments furnished additional dewatering data.
Water content in each case was determined by weight
of sludge before and after oven drying.
5.2.7.2 Dewatering Test Results
Consistency of Shawnee and Mohave sludges dewatered
by various means is shown on the respective bulk density/solids con-
tent curves (Figures 5-1 and 5-2). For both sludges, the most effec-
tive water removal process considered is vacuum filtering followed in
rank by centrifuging, free draining, and settling. A 5 - 10 percent
difference in attainable sludge dryness separates the different pro-
cesses applied to a given sludge.
Dewatering of Shawnee sludge (Figure 5-1) only re-
moves water in excess of the amount required to saturate the sludge.
By contrast, filtering of Mohave sludge removes water from between
the sludge particles, resulting in a filter cake containing less than the
saturation amount of water. Approximately 20 weight percent more
water is removed from Mohave sludge than from Shawnee sludge,
using the same dewatering techniques.
5. 3 ANALYSIS AND EVALUATION
The physical properties of sludges may limit or restrict
the possible methods of handling and disposal. The two sludges thus
far investigated were produced by eastern and western coals. How-
ever, the observed sludge behavior was not a consequence of the geo-
logical origin of the coal, but rather was a consequence of the phase
constituents in the sludge. In the Mohave system, an electrostatic
precipitator exists upstream of the scrubbing unit; thus, the sludge
contained less than 3 percent fly ash. The Shawnee system does not
5-22
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have a precipitator upstream of the scrubbers, and the resulting
sludge contains about 40 percent fly ash. In addition, the Mohave
sludge is more than 75 percent oxidized to the sulfate, whereas the
Shawnee sludge is oxidized to only 20 - 25 percent sulfate. Most
of the behavioral differences between the two sludges can be attrib-
uted to the degree of fly ash and sulfite content. The Mohave sludge
has characteristics much like sandy clay; this can be related to a
high percentage of bulky sulfate particles surrounded by platey sul-
fite particles. The Shawnee sludge behaves more like a silty clay
and can be understood in terms of the presence of bulky sulfate par-
ticles, fly ash, and residual limestone that constitutes more than
60 percent of the total quantity of sludge.
Many of the physical properties determined on these
sludges were found to be strongly dependent on water content. The
behavior of sludge either while being handled for disposal or after
being placed in a disposal site will be strongly affected by its water
content. Moreover, for the two sludges investigated, equivalent
water content did not produce equivalent behavior. If a sludge is to
be disposed of by ponding, the bulk density of the Shawnee sludge
would reach only 45 percent solids if placed in an impervious liner
such as clay or plastic, but if allowed to drain freely, it would reach
about 52 percent solids. The Mohave sludge settles to 67 percent
solids irrespective of its ability to freely drain. Centrifugation with
a laboratory centrifuge produces a material containing 55 percent
solids from the Shawnee sludge and 75 percent solids from the Mohave
sludge. {Centrifugation in a porous cup would be expected to give a
solids content 10 percent greater than that resulting from an impervi-
ous cup. Centrifugation with an industrial centrifuge is expected to
give a product somewhere between these two values and will depend
somewhat on Centrifugation rate.) By vacuum assisted filtration, the
Shawnee sludge dewatered to a value of 65 percent solids whereas the
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Mohave sludge reached a value of 80 percent. In this case, filtration
with an industrial filter is not expected to be as effective as labora-
tory filtration.
In each case, the Mohave sludge attained a higher
solids content than the Shawnee sludge regardless of the dewatering
method. These results were expected when the relative amounts of
sulfite in the two sludges were considered.
In a pond disposal method, the Mohave sludge will set-
tle or if dewatered, will attain a solids content great enough to sup-
port personnel. A very small amount of subsequent drying would be
adequate to support equipment. In contrast, the Shawnee sludge will
not settle or be dewatered sufficiently for support of personnel until
a solids content of 65 percent is reached. Support of equipment would
require greater than 70 percent solids; this could be accomplished if
the sludge were dried after dewatering. This drying could take place
in the pond during dry seasons. Rewetting during rain could return
the pond to the condition in which personnel and equipment could not
be supported. These values represent the minimum support loads and
do not represent recommended working consistencies.
The drainability of the Shawnee sludge is similar to
many natural soils. If the disposal site were such that liquors and
rain water were allowed to pass through it, the sludge would provide
no hindrance. Although drainability experiments on the Mohave sludge
are not yet completed, its drainage rate is greater than that of the
Shawnee sludge and more typical of soil with a high sand content.
Rain waters would easily percolate through such a sludge and would
not collect on the surface.
Neither sludge was found to develop strength during
settling by pozzolanic reaction or other means. Thus, except for
the compaction strength that develops during drying or dewatering,
no property change is observed to take place with time. Without
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specific chemical additions, the sludge does not develop resistance
to subsequent leaching.
Whereas the lack of strength build-up with time may
not aid in its use as a landfill, it does provide a material that can be
easily removed or transported regardless of time. For this purpose,
pumping the sludge as a slurry is the most economical means of trans-
portation. For the Shawnee sludge, the viscosity rises regularly with
an increase in solids content. Pump requirements can be easily deter-
mined from the measured relationship. In contrast, for the Mohave
sludge, the slurry behaves much like water up to 60 percent solids,
but between 60 and 65 percent solids the viscosity rises very fast.
In this case, optimum pumping could be done at 60 percent solids,
but close control of the solids content must be maintained to prevent
the solids content from getting too much higher to prevent pump over-
loading or the possibility of plugging a transfer pipe.
The tests on corrosion revealed that the corrosiveness
of the sludge is related to the pH of the liquor and that no enhancement
takes place except for one condition. If a metal container is in simul-
taneous contact with both sludge solids and liquor in a stagnant condi-
tion where an oxygen solution gradient can be maintained, an anodic
reaction takes place that releases iron from that portion of the steel
in contact with the solids. The iron subsequently reacts with the dis-
solved sulfate ions in the liquor and results in the deposition of sul-
fate compounds that form an encrustation on the metal part.
The physical property measurements on the Shawnee
and Mohave sludges have revealed differences in their behavior that
can be ascribed, at least in part, to the sulfate content and the pres-
ence or absence of fly ash in the sludge. The Mohave sludge has some
properties, primarily dewatering behavior, that are more desirable
for disposal. These properties should be useful in the development
of engineering design criteria for sludge disposal technology.
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5.4 STATUS AND PLANS
All physical property measurements have been made
on both Shawnee and Mohave sludges, except for completion of drain-
ability measurements on the Mohave sludge. The physical proper-
ties relating to sludge disposal technology will be determined for the
sludges from a lime scrubbing system and the double alkali system.
5-26
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SECTION 6
DETERMINATION OF ENVIRONMENTALLY SOUND
DISPOSAL METHODS
6. 1 STATEMENT OF PROBLEM
The surveys and analyses made to date in this program,
including reviews of technical papers published in the industry, have
indicated strongly that stack gas sulfur dioxide (SO2) scrubbing is
cause for major concern for the environmentally sound disposal of
the resultant sludge. With the production of sludge and fly ash of up
to 1.4 million tons/year/1000 MW capacity, massive quantities of
materials will have to be dealt with when the scrubbers become fully
operational (Ref. 6-1). If the sludge is treated so that it may be used
in the production of commercial products or used otherwise in some
form of commercial application, the disposal problem could be mini-
mized. However, based on surveys of marketing and commercial
planning activities in this country it appears that commercial utiliza-
tion will consume only a small and inconsequential percentage of the
total sludge that will be produced. Several research programs by both
industry and the federal government have determined technical appli-
cations that would consume reasonable amounts of sludge if those
6-1
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materials could be marketed. A brief summary of the potential
commercial utilization status is given in Appendix D. The conclusion
drawn in that assessment is that, "indications are that the potential
sludge products will not compete well enough in the near term to con-
sume an appreciable portion of the projected (sludge) supply and that
the principal concern for the sludge will be disposal and not utiliza-
tion." Even if commercial utilization could absorb a large percentage
of the sludge supply, the disposal process would still be a major prob-
lem requiring technical solutions. The difference would be that some-
what smaller amounts would have to be dealt with in the disposal area.
This section discusses the various methods by which
power plant sludges may be disposed of, the problems associated with
each method, progress being made, potential solutions, and costs.
These discussions center around the fact that lime and limestone
sludges present problems of considerable magnitude because of the
following factors:
a. The sludges contain many trace elements and dissolved
solids that are not allowed in surface or ground waters
from which drinking water supplies are withdrawn.
b. Quantities of total wastes are involved up to as much
as three times the tonnage of fly ash normally pro-
duced at a given power station.
c. The ability for the soil to prevent the leaching of harm-
ful constituents to ground or surface waters is not well
understood such that the impoundment of sludges with-
out using specific safeguards to prevent seepage is
considered a high risk approach.
Presently, the disposal alternatives being considered
are ponding and landfilling; both disposal operations will require the
establishment of procedures that avoid hazards related to health and
safety. The requirements for disposal of a particular sludge will be
strongly dependent upon whether or not it is found to be toxic. If the
sludges are found not to be toxic, the problem of disposal may be
6-2
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simplified, but the problem of water quality and possibly land use
must still be addressed. An untreated sludge will retain a consider-
able quantity of water. Laboratory tests on a limestone sludge con-
taining a relatively high sulfate content will settle only to 45 percent
solids content if underdrainage is not provided, but if drainage to sub-
soil is allowed, the settled sludge will reach a content greater than
50 percent solids. A maximum particle packing equivalent to a value
of about 70 percent solids content is reached upon air drying.
When a dried sludge is rewetted, the sludge can bloat
and decrease its bulk density depending upon the quantity of water
absorbed by the sludge. When a sludge contains a high sulfite con-
tent, the sludge will settle to a value of about 35 percent solids whether
underdrainage is provided or not. A sulfite sludge does not dry as
readily or settle as much during drying as a sulfate sludge.
A sulfate sludge for which underdrainage is provided
will produce savings relative to one with no such provision because
the higher packing density allows for the disposal of about 20 percent
more sludge in the same ponding volume. However, if the subsoil is
the only means of underdrainage, the possibility for soil plugging exists
especially in the case of sulfate sludges containing high concentrations
of dissolved solids. Depending upon soil type, salts will precipitate
within the soil, fill the pores, and prevent further water passage.
Thus, the advantage of underdrainage would be lost. The more reli-
able system is one in which underdrainage is provided. Although in
this case the sludge is assumed not to be toxic, it is very likely that
the leachate would not be of a quality to be acceptable for discharge
to a water course because of the high content of dissolved solids in
the sludge liquors.
Ponding can be used not only for the final disposal of
the sludge, but also as an interim measure to allow settling before
6-3
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removing the material to a landfill site. The most fundamental
problem in the environmentally sound disposal of the sludge arises
when the hazard exists for leaching toxic elements or soluble salts
to ground or surface waters, or drainage to surface waters. The
immediate solution to this potential problem may require dewatering
and/or fixation of the sludge and/or storing it in a clay-lined pond so
that permeation to the subsoil is minimized. Overdrainage and under-
drainage return liquor waters to the scrubber system thereby elimi-
nating direct discharge to surface waters. Such a pond can serve as
a final disposal site, but in some cases because of the large volumes
of sludge and water to be handled, the pond can serve as a primary
settling basin from which the sludge can be periodically removed and
placed in a landfill. A fixation treatment applied to the sludge prior
to placing it in the pond is an alternative technique generally applicable
only if the sludge is to be removed to a landfill after curing. This
treatment has two purposes: removing water and increasing strength
qualities, and minimizing leaching by decreasing the permeability of
the material.
If a sulfate sludge is found to be toxic, it may be ade-
quate to store it untreated in a pond having an impervious base. The
use of underdrainage and overdrainage would minimize inadvertent
leaching and the possibility of overflow, especially in areas where
rainfall exceeds evaporation. This, of course, requires the lining of
a large area pond, monitoring, and maintenance, as necessary. A
further problem would be faced when a point in time is reached where
the generating plant can no longer accept all drainage originating from
rainfall from all its disposal ponds and direct discharge to streams
would not be allowed, or where the plant is to be abandoned. Under
either of these conditions, encapsulation by covering with an impervi-
ous material may be the best solution.
6-4
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Numerous alternatives for ponding with or without pond
lining or sludge conditioning may be possible. Surveys of the industry
have shown that many of these alternatives are presently being con-
sidered and employed. Alternatives, such as treatment processes
mentioned earlier, produce a high solids content sludge material hav-
ing acceptable structural qualities for a landfill usage; also, a process
for producing aggregate has been developed.
Based on the considerations just mentioned, this pro-
gram has investigated various disposal techniques including chemical
fixation and pond linings, either of which may be adequate to contain
the sludge indefinitely. These two methods, though not technically
proven for long-time service, are considered to be the best techni-
cally and economically feasible approaches for solving the sludge dis-
posal problem. Their characteristics, problems, potential solutions,
and the characteristics of disposal without environmental protection
are the bases for the following discussions.
6.2 POTENTIAL DISPOSAL METHODS
6.2.1 Raw Sludge Disposal Without Environmental
Protection
The disposal of raw sludge into a pond, impoundment
basin, ravine, or water course without some form of environmental
protection is not considered sound at this time. However, attempts
are being made at power plant sites in Kansas, Alabama, and Ken-
tucky to dispose of raw sludge in ponds without providing a chemical
fixation of the sludge or a pond lining. The Kansas sites, which in-
clude the disposal of raw sludge into ponds in a manner similar to
that in which fly ash is commonly disposed of, are being monitored
to determine changes in the quality of ground waters in the immediate
area. At the Alabama site the sludge will be sluiced to the pond and
allowed to settle in a clay deposit. This site will also be monitored
6-5
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with regard to potential ground and surface water pollution. At the
Kentucky site the sludge is dewatered by filtration, and dumped and
compacted into the disposal site. It has been estimated by many mem-
bers of the power and environmental regulatory community that these
approaches will not be environmentally sound because of the potential
leaching of heavy metals and dissolved solids to the ground or surface
waters. These sites have not been investigated in detail during the
first phase of this study; however, they will be surveyed and assessed
later in this program. A discussion is given in Section 6.4 of raw
sludge disposal without pollution controls and the environmental im-
pact of fly ash on sludge disposal.
6. 2. 2 Lined Ponds
Raw sludge can be impounded in ponds that are lined by
various materials to a high degree of impermeability such that leach-
ing to water is minimal. Linings can be made from materials ranging
from compacted clays to concrete, plastics, or even some types of
chemically fixed sludge. In each case the liner prohibits leaching and
generally surface waters are recycled to the scrubber system to mini-
mize the volume of impoundment required while allowing reuse of the
pond liquors as an absorbent in the scrubber. The principal problems
associated with this form of disposal are: (a) the lack of technical data
to establish the ability to restrict excessive leaching for very long
times, and (b) the build up of a high water retentive mass that may
require special, yet undefined consideration for the reclamation of
this land after disposal is completed. Additionally, such a pond may
require continual monitoring for leaks and in some cases, depending
on the demands of the local regulatory authorities, special construc-
tion to channel and contain any leakage. The details associated with
ponding design are given in Section 6. 5.
6-6
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6.2.3 Sludge Conditioning
The fixation of sludges through chemical conditioning
processes offers the greatest environmentally sound approach to their
disposal. The purpose of the conditioning processes is to create a
material that is: easy to handle, highly impermeable and/or insoluble
such that the problem of contamination from leaching is eliminated,
and amenable to land reclamation. At this time considerable research
and development have been carried out by private industry, and some
of these developers are under contract to perform either partial or
full-scale sludge disposal operations at power plants now operating or
soon to be operating stack-gas scrubbers on a full-scale basis. Con-
siderable monitoring of these disposal sites will be performed by the
site operator and randomly by state or local regulatory authorities.
Monitoring is considered mandatory at this time because the long-term
effects of the conditioning process have not been proven. Discussion
of these processes, problems, and potential solutions and costs are
given in Section 6.6
6. 3 INDUSTRIAL AND GOVERNMENT PROGRAMS
Since the purpose of this portion of the Aerospace study
is to assess the status of the technology related to the environmentally
sound disposal of sludges, it has been necessary to visit many indus-
trial organizations and government agencies to gather the necessary
data. Contacts have been made with electric power companies, sludge
conditioning processors, federal and state environmental agencies,
and universities. Although some of the developments are similar, it
can be said that no two are alike at this time. Many of the power com-
panies involved in disposal program developments have been contacted;
however, no company is operating continually on a full-scale basis.
Some are in the pilot stage phase, others are operating prototype units,
and a few are operating or building full-scale units. A listing of the
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scrubber units now being developed or operated in the United States,
with an identification of flue gas desulfurization techniques, is given
in Tables 6-1 through 6-6. Also descriptions of current developments
in some of the power industries are given in Appendix E. These in-
clude: Commonwealth Edison, Will County Station, Joliet, Illinois;
Northern States Power Company, Sherbourne County Station, Minne-
apolis, Minnesota; Louisville Gas and Electric, Paddy's Run Station,
Louisville, Kentucky; and Duquesne Light Company, Phillips Station,
Pittsburgh, Pennsylvania. The developments in these stations are all
different and include the following approaches, respectively:
a. Chemical fixation performed by the power company
and material dumped in an unlined landfill
b. Raw sludge to be dumped in clay-lined basins
c. Dried sludge dumped in an unlined basin
d. Sludge chemically conditioned by a commercial
process and to be dumped in unlined ponds
None of these four has demonstrated its selected processes on a con-
tinuing operational basis. During the remainder of this program, con-
tact will be made with these stations to determine their progress, and
problems and solutions. Additionally, other stations now planning or
developing similar operations for sludge disposal will be contacted
(e.g., the Ohio Edison Company's Bruce Mansfield Plant, a 1650 MW
station, which will probably have all of its sludge chemically fixed and
pumped to a disposal ravine approximately 6 to 8 miles away). Con-
tacts will also be made with Kansas City Power and Light, and Kansas
Power and Light, both of which are investigating the disposal of raw
sludge in unlined ponds. Other stations to be contacted include, but
are not limited to, the following: Detroit Edison, St. Clair Station;
TVA, Widow's Creek Station; Montana Power, Colstrip Station; and
Arizona Public Service, Cholla Station.
6-8
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Table 6-1. PLANNED AND OPERATING FLUE GAS DESULFURIZATION (FGD)
UNITS ON U.S. POWER PLANTS AS OF SEPTEMBER 1973--
LIMESTONE SCRUBBING SYSTEM
Source: EPA Control Systems Laboratory, Nonregenerable Processes Section
Utility company and
power station
Commonwealth Edison
Will County No. 1
Kansas City Power and Light
Hawthorn No. 4
Kansas City Power and Light
LaCygne Station
Arizona Public Service
Cholla Station
Detroit Edison
St. Clair No. 6
Southern California Edison
(operating agent)
Mohave Station
Tennessee Valley Authority
Widow's Creek No. 8
Northern States Power
Sherbourne County No. 1
Public Service of Indiana
Gibson Station
Northern States Power
Sherbourne County No. 2
New or
retrofit
R
R
N
R
R
R
R
N
N .
N
Size of FGD
unit (MW)
156
100
820
115
180
160
550
680
650
680
Process
vendor
Babcock and
Wilcox
Combustion
Engineering
Babcock and
Wilcox
Research
Cottrell
Peabody
Engineering
Universal Oil
Products
Tennessee Valley
Authority
Combustion
Engineering
Combustion
Engineering
Combustion
Engineering
Fuel and
sulfur content, %
Coal, 3.5
Coal, 3. 5
Coal, 5.0
Coal, 0.4 - 1.0
Coal, 3.7
Coal, 0. 5 - 0.8
Coal, 3.7
Coal, 1.0
Coal, 1.5
Coal, 1.0
Status
(start-up date)
Operational
(February 1972)
Operational
(August 1972)
Operational
(June 1973)
Under construction
(October 1973)
Under construction
(December 1973)
Under construction
(March 1974)
Under construction
(May 1975)
Under construction
(May 1976)
Planned
(1976)
Planned
(May 1977)
vO
-------
Table 6-2. PLANNED AND OPERATING FLUE GAS DESULFURIZATION (FGD)
UNITS ON U.S. POWER PLANTS AS OF SEPTEMBER 1973--
LIME SCRUBBING SYSTEM
Source: EPA Control Systems Laboratory, Nonregenerable Processes Section
Utility company and
power station
Union Electric Co.
Meramec No. 2
Kansas Power and Light
Lawrence No. 4
Kansas Power and Light
Lawrence No. 5
Kansas City Power and Light
Hawthorn No. 3
Louisville Gas and Electric
Paddy's Run No. 6
Duquesne Light Co.
Phillips Station
Southern California Edison
(operating agent)
Mohave Station
Ohio Edison
Mansfield Station (2 units)
Montana Power
Colstrip Nos . 1 and 2
Columbus and Southern
Conesville Nos. 5 and 6
New or
retrofit
R
R
N
R
R
R
R
N
N
N
Size of FGD
unit (MW)
140
125
430
100
70
100
160
1650
720
750
Process
vendor
Combustion
Engineering
Combustion
Engineering
Combustion
Engineering
Combustion
Engineering
Combustion
Engineering
Chemico
SCE/Stearns -Roger
Chemico
Combustion
Engineering
Not selected
Fuel and
sulfur content, %
Coal, 3.0
Coal, 3. 5
Coal, 3. 5
Coal, 3. 5
Coal, 3.0
Coal, 2.0
Coal, 0. 5 - 0. 8
Coal, 4. 3
Coal, 0.8
Status
(start-up date)
Abandoned
(September 1968)
Operational
(December 1968)
Operational
(November 1971)
Operational
(November 1972)
Operational
(April 1973)
Under construction
(November 1973)
Under construction
(December 1973)
Under construction
(Early 1975)
Under construction
(May 1975)
Planned
(1976)
I
t»
o
-------
Table 6-3. PLANNED AND OPERATING FLUE GAS DESULFURIZATION (FGD)
UNITS ON U.S. POWER PLANTS AS OF SEPTEMBER 1973--
LIMESTONE OR LIME SCRUBBING NOT SELECTED
Source: EPA Control Systems Laboratory, Nonregenerable Process Section
Utility company and
power station
Salt River Project
Navajo No. 1
Salt River Project
Navajo No. 2
Arizona Public Service
Four Corners No. 1
Arizona Public Service
Four Corners No. 2
Southern California Edison
(operating agent)
Mohave Nos. 1 and 2
Arizona Public Service
Four Corners No. 3
Salt River Project
Navajo No. 3
Arizona Public Service
Four Corners No. 4
Arizona Public Service
Four Corners No. 5
New or
retrofit
N
N
R
R
R
R
N
R
R
Size of FGD
unit (MW)
750
750
175
175
1180
229
750
800
800
Process
vendor
Not selected
Not. selected
Not selected
Not selected
Not selected
Not selected
Not selected
Not selected
Not selected
Fuel and
sulfur content, %
Coal, 0.5-0.8
Coal, 0. 5 - 0.8
Coal, 0.75
Coal, 0.75
Coal, 0. 5 - 0.8
Coal, 0.75
Coal, 0.5-0.8
Coal, 0.75
Coal, 0.75
Status
(start-up date)
Construction start,
November 1974
(March 1976)
Construction start,
October 1975
(October 1976)
Construction start,
October 1975
(October 1976)
Construction start,
November 1975
(December 1976)
Planned
(December 1976)
Construction start,
June 1976
(March 1977)
Construction start.
March 1976
(March 1977)
Construction start,
September 1975
(April 1977)
Construction start,
November 1976
(June 1977)
-------
Table 6-4. PLANNED AND OPERATING FLUE GAS DESULFURIZATION (FGD)
UNITS ON U.S. POWER PLANTS AS OF SEPTEMBER 1973--
MAGNESIUM OXIDE SCRUBBING SYSTEM
Source: EPA Control Systems Laboratory, Nonregenerable Process Section
Utility company and
power station
Boston Edison
Mystic No. 6
Potomac Electric
and Power
Dickerson No. 3
Philadelphia Electric
Eddys tone No. 1
New or
retrofit
R
R
R
Size of FGD
unit (MW)
150
100
120
Process
vendor
Chemico
Chemico
United
Engineers
Fuel and
sulfur content, %
Oil, 2. 5
Coal, 2.0
Coal, 2.5
Status
(start-up date)
Operational
(April 1972)
Operational
(September 1973)
Under construction
(December 1973)
-------
Table 6-5. PLANNED AND OPERATING FLUE GAS DESULFURIZATION (FGD)
UNITS ON U.S. POWER PLANTS AS OF SEPTEMBER 1973--
OTHER SULFUR DIOXIDE CONTROL SYSTEMS
Source: EPA Control Systems Laboratory, Nonregenerable Process Section
Control system, utility com-
pany, and power station
Catalytic Oxidation (Cat-Ox)
Illinois Power Co.
Wood River No. 4
Wellman- Lord
Northern Indiana
Public Service
D.H. Mitchell No. 11
, Aqueous Sodium Base Scrub-
>- bing, Nonregenerable
Nevada Power
Reid Gardner
Nos . 1 and 2
Nevada Power
Reid Gardner No. 3
Dry Adsorption
Indiana and Michigan
Electric
Tanner's Creek Station
New or
retrofit
R
R
R
R
R
Size of FGD
unit (MW)
110
115
250
125
150
Process
vendor
Monsanto
Davy Powergas/
Allied Chemical
Combustion
Engineering
Combustion
Engineering
Babcock and
Wilcox/Esso
Fuel and
sulfur content, %
Coal, 3.2
Coal, 3.5
Coal, 0. 5 -
1.0
Coal, 0. 5 -
1. 0
Coal
Status
(start-up date)
Operational
(October 1972)
Under construction
(Early 1975)
Under construction
(December 1973)
Under construction
(1975)
Under construction
(1974)
-------
Table 6-6. PLANNED AND OPERATING FLUE GAS DESULFURIZATION (FGD)
UNITS ON U.S. POWER PLANTS AS OF SEPTEMBER 1973--
PROCESS NOT SELECTED
Source: EPA Control Systems Laboratory, Nonregenerable Process Section
Utility company and
power station
Public Service of
New Mexico
San Juan No. 2
Potomac Electric and Power
Chalk Point No. 3
Potomac Electric and Power
Chalk Point No. 4
Potomac Electric and Power
Dickerson No. 4
Potomac Electric and Power
Dickerson No. 5.
New or
retrofit
R
N
N
N
N
Size of FGD
unit (MW)
100
630
630
800
800
Process
vendor
Not selected
Not selected
Not selected
Not selected
Not selected
Fuel and
sulfur content, %
Coal, 0.8
Oil
Oil
Coal, 2.0
Coal, 2.0
Status
(start-up date)
Planned
(November 1974)
Planned
(1975)
Planned
(1976)
Planned
(1976)
Planned
(1977)
-------
The status of the development of sludge fixation technology
has been reviewed with three companies: The Dravo Corporation,
International Utilities Conversion Systems, Inc. (IUCS), and Chem-
fix. Each of these produces a "nonleachable material suitable for
landfill usage. " At this time Dravo is providing the chemical
fixation admixture for a sludge disposal program at the Duquesne
Light Company, Phillips Station, Pittsburgh, Pennsylvania, and to
perform a demonstration program at the Mohave Station in Nevada.
They are also negotiating to dispose of the Ohio Edison Bruce Mans-
field Plant's sludge using the Dravo fixation process and pumping the
sludge to the disposal ravine. They would maintain and monitor this
disposal site and pump pond liquor back to the scrubber. Conversion
of some sludge from the Mohave Station's limestone scrubber to an
artificial aggregate will be demonstrated by IUCS; they will haul the
aggregate away for commercial usage. Chemfix, though commercially
conditioning industrial sludges at this time, is not yet conditioning any
sludges for the power industry. Continuing contacts with these three
companies and others who may become significant in this field will be
made throughout the remainder of this program. More detailed des-
criptions of these three fixation processes are given in Section 6.6.
6.4 RAW SLUDGE AND ASH DISPOSAL WITHOUT
POLLUTION CONTROLS
6. 4. 1 Introduction
Several alternative methods are available to power plants
with regard to disposal of fly ash and SO? sludge. Of the two dozen
power stations in the United States that are committed to lime or lime-
stone scrubbers, the method of disposal of fly ash and sludge is either
not fully defined or, if defined, each differs in both philosophy and
practice from any other station. Whereas most power companies are
taking some precaution in the disposal of their sludge relative to the
6-15
-------
prevention of environmental pollution, others are not. In considering
the many alternative disposal methods possible, it is conceivable that
a relatively large number of power stations that will eventually use a
lime or limestone scrubber will attempt not to provide environmental
control of their waste products. It is the potential hazard created at
these power plants that the following discussion addresses.
A majority of the nation's power plants are located along
the banks of a major watercourse. The most prevalent method of fly
ash disposal has been by sluicing it to lagoons, usually using cooling
tower blowdown, and returning the water to the watercourse after the
suspended solids have settled out. Chemical analyses of discharges
have been made from EPA Region V Power Plants, and specific atten-
tion has been paid to the discharge originating from ash ponds. One
large power plant (Ohio Power, Muskingham River Plant) located along
the Ohio River is of particular interest because the chemical charac-
teristics of its pond discharge are considered typical for that region.
This plant, which represents about 2 percent of the electrical power
generated along the Ohio River and its tributaries, returns 1.4 mil-
lion gallons of water to the Ohio River daily through its ash pond dis-
charge. In each year there is emitted with this water: 19 lb of anti-
mony, 390 lb of boron, 1.3 lb of beryllium, 104, 000 lb of calcium,
9 lb of chromium, 4. 7 lb of copper, 6. 4 lb of lead, 25 lb of selenium,
and 8 lb of zinc. The chemical trace analysis of the fly ash lagoon
outflow from this plant is given in Table 6-7. It is unfortunate that
the important toxic elements, arsenic and mercury, were not included
in the list of elements analyzed by this plant; therefore, the total extent
to which the industry's fly ash lagoons contribute to pollution is unknown.
Using this plant as an example, we examined the effluent
emitted under the following two conditions that are possible if lime or
6-16
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Table 6-7. OHIO POWER, MUSKINGHAM RIVER PLANT
ASH POND DISCHARGE
Discharge
pH
Aluminum (Al)
Antimony (Sb)
Barium (Ba)
Beryllium (Be)
Boron (B)
Bromide (Br)
Calcium (Ca)
Chromium (Cr)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Nickel (Ni)
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Selenium (Se)
Silver (Ag)
Amount
7. 5
190.0 ppb
45.0 ppb
120.0 ppb
3 . 0 ppb
920.0 ppb
0.13 ppm
243. 0 ppm
21.0 ppb
17.0 ppb
1 1 . 0 ppb
190.0 ppb
15.0 ppb
46 . 0 ppm
233.0 ppb
24. 0 ppb
18. 0 ppm
0. 24 ppm
12.0 ppm
58. 0 ppb
5. 0 ppb
Discharge
Sodium (Na)
Tin (Sn)
Zinc (Zn)
Acidity
Alkalinity
Ammonia
Chloride
Nitrate
Nitrite
Sulfate
Total dissolved
solids
Total suspended
solids
Total volatile
solids
Total solids
Amount
171.0 ppm
32.0 ppb
18.0 ppb
4. 0 ppm
164. 0 ppm
6 . 0 ppm
310.0 ppm
1.13 ppm
0.18 ppm
110. 0 ppm
1 170 ppm
53 ppm
469 ppm
1 237 ppm
6-17
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limestone scrubbers are installed on the flue stacks, and no controls
are used to protect the quality of ground or surface waters:
a. Fly ash and SO2 sludge are collected separately and
disposed of in a fly ash lagoon and a sludge pond,
respectively.
b. Fly ash and SO2 sludge are collected separately or
together, and both are disposed of in a sludge pond.
Additionally, a discussion is given of a variation of (b), as follows:
fly ash is used as the SO2 sorbent; the sludge (containing fly ash) is
disposed of in a sludge pond.
These three cases are discussed in Sections 6.4.2,
6.4.3, and 6. 4. 4, respectively.
6-4.2 Separate Ash and Sludge Collection and
Separate Disposal
It is presumed that the sludge pond would be enclosed,
and that no liquor could flow directly into the river. However, since
the plant is located near the river bank, the pond would be just above
or possibly into the water table. The sludge will contain about 50 per-
cent of its mass as water, but experiments have shown that sludge
does not offer resistance to drainability; thus, leachate liquors from
the sludge pond have direct or nearly direct access to the water table
and, thereby, access to the river. The metal loading from the ash
pond discharge to the river remains unchanged.
The sludge pond will contain liquors high in dissolved
solids with total concentrations approaching 2 percent. Combined cal-
cium ions and sulfate ions are expected to be present at a concentra-
tion of 0.4 percent, chloride ions at 0. 5 - 1.0 percent, and other
cations represented by Na, K, B, Mg, Mn, and others at 1 percent
or greater. Among these others, arsenic (As), mercury (Hg), and,
to a lesser extent, cadmium (Cd) are expected as dissolved solids in
6-18
-------
the liquor. The origination of these three cations and chloride ions--
all products of coal combustion--is a consequence of scrubbing flue
gas.
Normally, elemental Hg and Cd are volatilized in the
combustion of coal and enter the atmosphere with the flue gas. In
addition, the chlorine in the coal forms gaseous hydrogen chloride
and will also be emitted with the flue gas. When the flue gas is
scrubbed by either a lime or limestone sorbent, hydrogen chloride
(HC1) is readily scrubbed from the gas. Existing data suggest that
SCU scrubbing units are at least 90 percent effective in removing HC1
from the flue gas. Since chlorine forms so few insoluble salts, chlo-
ride ions will not precipitate as a solid. It is assumed that the scrub-
bing liquor remains in a closed-loop system with the only purge being
the water that is disposed of in the sludge. The chloride ion will then
build up to a concentration of equilibrium such that the amount of chlo-
rine entering the scrubbing system from the flue gas will be balanced
by the chlorine disposed of in the liquor fraction of the sludge. For
typical concentrations of chlorine in coal this value will approach 1 per-
cent in a well regulated closed-loop system.
The chloride ion serves a useful purpose in the scrub-
bing operation because its presence in the liquor will promote the solu-
tion of elemental Hg scrubbed from the flue gas and will result in the
precipitation of the highly insoluble mercurous chloride (Hg2Cl2); the
flue gas is thereby effectively scrubbed of Hg by chloride ions in the
scrubber. However, Hg is easily oxidized and when the Hg?Cl? pre-
cipitate is subsequently disposed of in the pond, the higher oxidation
potential that exists there relative to the scrubber or hold tank will
convert the Hg to mercuric chloride (HgCl2), a salt that is highly sol-
uble. Data thus far obtained, indicate that this oxidation readily takes
place. Since most, if not all, ponds are being provided with a liquor
recovery system as part of the closed loop, the Hg-ion laden liquors
6-19
-------
will be recirculated to the scrubber. The consequence will be a
build-up of Hg ions in the recirculation liquors. The equilibrium
concentration at which the system will come into balance has the
potential of being appreciably high (>50 ppm) depending on scrubber
design parameters and Hg content of coal; the consequence can be a
highly toxic pond liquor.
Cadmium too can be scrubbed from the flue gas, but
in this case, the carbonate ion is the effective sorbent. Cadmium
carbonate is an insoluble salt that will precipitate in the scrubbing
system. Since the equilibrium concentration of carbonate ion in the
system is at least one or more orders of magnitude greater than the
Cd content, the soluble Cd content is expected to be very low. More-
over, liquor recirculated to the pond would be expected to reach equi-
librium with CO., in the atmosphere; resolubility, as in the case of Hg,
would not be expected to take place.
A third element, As, is also scrubbed from the flue
gas; however, As does not enter as a gas but as a solid. Approxi-
mately 1 percent by weight of the total particulates produced during
combustion passes through the precipitators. These particles con-
stitute the super-fines having very high surface areas. Analyses of
these particles indicate that they contain about 20 percent of the As
originating from the coal. Wet scrubbing removes these particles
from the flue gas and the As becomes easily dissolved in the scrub-
bing liquor. Arsenic does not form stable (insoluble) compounds with
the anions in the lime-limestone system and builds up within the liquor
as a dissolved solid. Analysis of liquors from a closed-loop recircu-
lation system has shown that a level of dissolved As in excess of safe
limits is possible, and this value may not even have reached the equi-
librium saturation level.
The foregoing arguments reveal that flue gas scrubbing
for 862 removal can also remove Hg and As that might otherwise be
6-20
-------
distributed to the atmosphere. In so doing, however, the recirculation
liquors can reach high levels and create a potential hazard in sludge
disposal. Thus, sludge liquors having access to the watercourse can
easily and readily create a problem of water pollution as a consequence
of air pollution prevention. In the present case, typical of a majority
of power plants using eastern coal, Hg and As would be leachable to the
river (see Section 6.4.3) as contaminants in addition to those originat-
ing from the fly ash lagoon. The net effect is not known, except that
the following case can be more severe.
6.4.3 Ash and Sludge Mixed and Disposed of in
Sludge Pond
Fly ash can be collected in the scrubber or it might be
collected separately and added to the sludge at the sludge pond. Either
way, soluble elements that otherwise enter the river are now collected
in the sludge pond. However, recirculation of liquor will allow each
element to build up to an equilibrium concentration. The total level of
dissolved solids can reach and surpass 10 percent depending on the
particular elements in the system and their chemistry. Some elements
(e.g. , Pb and Be) will be controlled by sulfate or sulfite ions; others
(e.g., Mn and Cu) form insoluble carbonate salts. Other elements
[e.g., B and chlorine (C1)J do not form insoluble salts and will accu-
mulate in the recirculation liquors. The chemistry of other elements
is not yet understood. Although these elements are not directly dis-
charged to the river, their presence in an uncontrolled sludge pond
makes them available by passage through the water table to the river.
An important aspect of this indirect discharge must be
considered. The surface of a sludge pond will normally lie above the
water table such that a hydraulic head from the pond can effect an
order of magnitude increase in the permeability of the leachate through
the aquifer. While access to the river is a function of many variables
6-21
-------
(such as geological location of the pond, subsurface soils, and flow
rate within the table), a major disadvantage exists for the typical pond
site. At pond locations adjacent to power plants located along a river-
bank, subsurface water lateral flow tends to be relatively rapid com-
pared to vertical flow. During summer months when the river level
is low, a major source of river rejuvenation can originate from drain-
age of the water table. At this time, the pond discharge potential to
the river is greatest because of the hydraulic head of the pond, and
the reduced or nonexistent hydraulic head effect of the river. The
drainage to the river from the pond through a saturated base soil con-
tains high concentrations of soluble elements accumulated throughout
the year, but discharged to the river during a period of low volume
and reduced flow rate.
In summary, the collection or combination of fly ash
with sludge and disposal in a single basin as part of a closed-loop sys-
tem, prevents the continuous pollution of river waters that results
from a fly ash lagoon operation. However, a periodic pollution prob-
lem can be created that is much more severe than that occurring from
separate ash lagoon and sludge pond operations if environmental con-
trols are not exercised on this disposal site.
6.4.4 Fly Ash Sorbent--Disposal in Sludge Pond
A further alternative for sludge disposal may consider
the use of fly ash as the sorbent. This is a situation that exists when
high-lime western coal is used. These coals often contain high lime-
stone such that there is sufficient lime in the fly ash to obviate the
need for lime or limestone additions to the scrubber. In addition, the
sulfur content of the coal is low; therefore, high flue gas scrubbing
efficiency need not be obtained to meet environmental standards. The
consequence is that the scrubber could be operated at lower than stoi-
chiometric that produces highly acidic sludge. The potential for
6-22
-------
environmental pollution created by this sludge is greater than that if
the sludge were neutral or basic. The major solid components in the
sludge--sulfites, sulfates, and carbonates--are all more soluble in
an acid condition than in a base condition. Quantitative increase in
solubility is not possible to predict in such a complicated chemical
system, but values ranging from a few percent to orders of magnitude
would be expected among the various heavy metal compounds typically
found in these sludges.
6.4.5 Comments
In each of the cases considered, the potential hazard
exists for environmental pollution as a consequence of disposing of SO7
sludge in an uncontrolled condition that is state-of-the-art for ash dis-
posal in the electrical power industry. Conditions relating to the soil
(sand/clay content), the geological and hydrological location of the dis-
posal site, weather, disposal site management, chemical contents of
the coal, scrubber type, and sorbent each have an effect on the real
pollution hazard. This hazard originates primarily as a consequence
of the concentrating capacity of sludge liquors and the further possibil-
ity of these liquors being discharged inadvertently to the environment.
Even in cases where sludge disposal sites are being con-
trolled by linings on ponds or by chemical fixation, there presently exists
a measure of uncertainty. Laboratory evidence has indicated that sul-
fate ions can saturate clays so as to render them ineffective in their ion
exchange capacity and thereby make them ineffective, in time, as a hold-
ing basin for sludge. Furthermore, the reliability of plastic lining
materials over long times is uncertain. Neither sufficient data nor ex-
perience with these materials presently exists to provide a quantitative
measure of reliability of any type of pond lining material. As an envi-
ronmental alternative there is the choice of chemical fixation, but these
techniques also have not been proven with time. The evaluation of the
alternative disposal techniques relative to their capability for environ-
mental protective capacity is now under study in this program.
6-23
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6. 5 LINED PONDS
6. 5. 1 Study Approach
Analyses were made to determine the technical and
economic details relating to disposal ponds capable of containing
sludge from the desulfurization scrubbers of power plant flue gases.
In the technical analyses, examinations were made of
the engineering design of sludge ponds with emphasis on 1 5 liner mate-
rials, liner installation techniques, liner maintenance and techniques
for repair, any limitations on pond usage, effects of the environment
on the liner materials, determination of ancillary equipment needed
to control the flow of sludge into or the effluent from the pond, and
the instrumentation and methods used for monitoring pond leakage or
seepage.
The economic analysis was directed toward determin-
ing the initial investment for the sludge ponds (including both the liner
installation and general contractor work) and the required ancillary
equipment, and the cost of the pond as a function of the kWh of elec-
tricity produced.
To acquire the data needed for the technical and eco-
nomic analyses, detailed discussions were held with representatives
from the liner fabricators, general contractors, power utility com-
panies, and other industries using evaporation and sludge disposal
ponds. These discussions were with companies operating through-
out the United States so as to obtain a full insight into the techniques
used in different parts of the country.
In all discussions it was assumed that present day tech-
nology would be used for the pond design and construction, and that all
costs are based upon 1973 prices.
6-24
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6.5.2 Pond Design
6. 5. 2. 1 General
During the technical evaluation phase of the study it
became evident that the useful life of a sludge disposal pond is depen-
dent upon the aging characteristics of the seepage barrier material.
The flexible liners have an age life of 20 to 25 years depending upon
the material and how it is used. The age life of the nonflexible liners
(e.g. , asphalt and concrete) may be more than 50 years, again de-
pending upon the design of the pond and degree of earth movement.
Only the clays may possibly have a longer, indefinite life cycle. When
selecting the specific liner material to be used as a seepage barrier,
consideration must be given to the following factors:
What is to be done with the pond after it has been
filled to capacity? Will it be treated further and
converted into a park or used for structural pur-
poses? Should plans be made at the time the ponds
are constructed to allow for removing the sludge
every 20 to 30 years and replacing the flexible
liner so as to ensure the integrity of the seepage
barrier? Should the philosophy be that the pond
liner is a permanent installation and no replace-
ments are to be made unless forced to do so be-
cause there is contamination of the surface or
ground waters ? Or, should dewatering drainage
be built into the pond?
At this time, the capabilities of the pond lining as to
permanent environmental protection are not known, and the consider-
ations that would be required if the disposal site is ever to be con-
verted to structural or nonstructural land usage have not been
determined.
6-25
-------
Because each pond is designed to perform a specified
function, the designs vary in accordance with the immediate soil con-
ditions, topography, weather conditions, the state and local pollution
control regulations, traffic within and surrounding the ponds, and
with the material to be contained.
The sludge pond configuration considered in this study
is essentially an excavated pit or basin with the soil graded into em-
bankments or dikes to add to the heights of the sidewalls. Figures 6-1
through 6-3 illustrate some of the general characteristics and key fea-
tures of typical ponds that use a flexible liner system for seepage
control.
The pond bottom is usually flat, but may be contoured
or pitched to drain off the liquid if so desired. The embankment slopes
are 2 to 1 or shallower for ease of construction, and the tops of the
embankments (berms) are at least 45.7 cm (18 in. ) wide to provide
sufficient structural support for the sides. In many cases the berms
are sufficiently wide and steady enough to support vehicles.
Many different types of pond liner materials are cur-
rently being used depending upon the specific purpose of the pond,
area to be covered, material to be contained in the pond, and the local
environmental conditions. The liners used and included in this study are:
Flexible Nonflexible
Polyethylene (PE) Soil cement
Polyvinyl chloride (PVC) Asphalt
(10 and 20 mil)
Concrete
Petromat fabric _ , .-,-, j u
Pozzolan stabilized base
Butyl rubber _
7 Gunite
Chlorinated polyethylene (CPE)
Olay
Hypalon
EPDM rubber
Fiberglass polyester
6-26
-------
ANCHOR METHOD No. 1
COMPACTED
EARTH SUBGRAOE
TOP OF SLOPE ANCHORAGE
ANCHOR METHOD No. 2
SLOPE TO DRAIN
LINING
- COMPACTED
EARTH SUBGRADE
EARTH AND GRAVEL COVER - FULL SLOPES
EARTH AND GRAVEL COVER - PARTIAL SLOPES
GRAVEL COVER
LIQUID LEVEL
GRAVEL COVER
LINING MATERIAL
EARTH COVER
SLOPE 2:1 OR LESS
COMPACTED
EARTH SUBGRADE
ANCHOR
METHOD
No. 1 OR No. 2
LIQUID LEVEL-.
EARTH COVER
ANCHOR
EARTH COVER No. 1 OR No. 2
SLOPE 2:1 OR LESS
-LINING MATERIAL
COMPACTED
-EARTH SUBGRADE
PATCH TO LAP HOLE
20 cm (8 in. i MINIMUM
ALL AROUND
SEAL TO PIPE
LINING-
HOLE IN PATCH SMALLER THAN
PIPE DIAMETER AND STRETCHED
OVER PIPE TO FORM FLANGE
ALTERNATE: OMIT PATCH AND
FORM FLANGE IN LINING
BONDING SOLVENT
TYPICAL FIELD LAP JOINT
5 cm
(2 in.)
MINIMUM
LINING v |i »| /- LINING
1.3 to 2.54 cm (1/2 to 1 in. |
WIDE BEAD BONDING SOLVENT
Figure 6-1. Typical pond features--flexible liner system
-------
TYPICAL OUTSIDE BERM N.T.S.
20 mil THICK (min)
IMPERVIOUS LINING (typical)
MANHOLE FRAME AND
COVER-BOLTDOWN TYPE
LEAKAGE DETECTION -
SUMP
WATERPROOF COATING -
COAL TAR ENAMEL OR
EQUAL
>--^ I KAta i in\j r~-~*^.-^
^-^_ / GROUND | _^-r^__ I
CLAY BARRIER
AT Q. OF EACH
POND BOTH WAYS
STRIP 6 In!(rnlrifBEFORE f
PLACING FILL
^t- MORTAR
-COMPACTED EARTH
FILL (native soil)
SLOPE
OF J
SAND
CLAY
LINING
MORTAR
-------
ROAD TRAFFIC
ON BERM SURFACE
DOUBLED BACK 0.0508 cm
(20 mil) PVC LINER
FREEBOARD 61 cm
(2ft) (minimum)
61 cm (2 ft) SALT
LAYER
Note: No provision is made for undordrainage
or overdrainage
yLIOUID LEVEL
35.6 to 45.7 cm (14 to 18 in.
15.2 cm (6 In.)
COMPACTED
SANDY SOIL
Figure 6-3. Potash evaporation pond features - -Texasgulf, Inc.
(not to scale)
Properties of these liners are given in Appendix C.
Leakage detection devices are sometimes incorporated
into the pond design. These devices vary from a simple underdrain-
age basin, to an electrical system designed to measure the electrical
resistivity of the ground in the pond area. Some pond installations
monitor the nearby surface and ground waters to determine if there
is leakage or seepage from the ponds.
6.5.2.2 Influence of Locale
The basic design features of disposal ponds are gen-
erally uniform throughout the country. However, there may be local
ordinances and environmental regulations that must be considered.
For example, if flexible liners are installed over decomposing mate-
rials or in areas of fluctuating water tables that pump air, bubbles
could develop, come to the surface, and be unable to escape because
of the liner's impermeability. Where these conditions exist, designs
6-29
-------
must be incorporated to vent the gases, and provisions must be made
to cover the flexible liner with soil to add weight and reduce the oppor-
tunity for it to float prior to adding sludge. Fencing is necessary
around all pond areas, but the size and type of fence will vary depend-
ing upon the vehicular, pedestrian, and animal traffic in the area.
6.5.3 Technical Data
The many different types of barriers that have been
developed over the years and employed to prevent seepage of liquids
into the ground include such varied materials as flexible liners, clays,
soil cement, asphalt, concrete, wood, and metals. Each type of mate-
rial in turn is composed of a number of items specifically designed
for a special application. Although all materials have a tendency to
reduce the liquid seepage rate from a pond or basin, the degree of
seepage through the material is a function of: material thickness,
material permeability, material to be contained, and amount of sup-
plemental covering over the liner.
6.5.3.1 Thickness
It is generally accepted that the thicker the barrier the
less opportunity a liquid has to penetrate the material. This is true
providing the barrier is a dense, homogeneous mass without porosity
or fissures. In designing disposal ponds, detailed trade off studies
are generally made; however, decisions appear to have been some-
what arbitrary in some cases that were examined. Thicknesses most
commonly used are: flexible: 0.0254 - 0.0762 cm (10 - 30 mil);
clay: 30.4 - 45.7 cm (12 - 18 in.); and asphalt or concrete: 15.2 cm
(6 in.).
6. 5. 3. 2 Permeability
Every material is permeable to some degree, the
amount depends upon such items as material density; the absence
6-30
-------
of cracks, pinholes, and foreign matter; and the head or pressure
forcing the liquid through the barrier. Factors such as the liquid
permeability, weatherability of the barrier, age life, fungus attack,
and fabrication/installation techniques can affect the permeability
over the operating life of the pond.
6. 5. 3. 3 Material to be Contained
The material to be contained in a sludge pond directly
influences the pond configuration and the construction materials.
Problems sometimes develop in sludge disposal ponds that are de-
signed to contain materials with pH values of under 4 or over 8, or
if there are organic compounds present that could act as a solvent for
the liner or be a basis for bacterial action. Fortunately, the chemi-
cal, precipitates of the effluent from the flue gas scrubbers are not
generally reactive to the standard flexible liner materials, asphalt
base liners, or clays. The sulfates in the sludge could react with the
soil cement and concrete and cause a breakdown of these liners.
6.5.3.4 Covering Over the Liner
When considering the amount of seepage through a liner,
consideration is given to any supplemental covering over the liner that
would enhance the barrier effect. There are two general types of cov-
ering: an artificial cover such as clay, soil, or secondary membrane
liner and the gradual build up and accumulation of solids being con-
tained in the pond. Although an artificial cover increases the pond
complexity and cost, this concept may be the only solution to reduc-
ing the seepage rate to the desired level or to protect the liner from
aging effects and mechanical damage. The exact cover type and thick-
ness will depend upon the liner to be protected, the head of liquid, the
permeability of the liner and cover, and the material to be contained.
In some situations the material to be disposed of will flocculate to a
6-31
-------
degree sufficient to add to the liner barrier effect and thereby reduce
the seepage rate. Every case is entirely different and must be evalu-
ated on its own basis.
6.5.4 Flexible and Nonflexible Liners
The materials that have been used for pond linings can
be broadly classified as plastics or rubbers, soils, and asphalt/
concretes. Appendix C contains descriptions of the key features of
some of these types of liners; cost data for the appropriate liners are
discussed in Section 7. 1. Table 6-8 summarizes the more significant
factors relating liner materials to sludge pond requirements.
6. 5. 5 Seepage Monitoring
6. 5. 5. 1 General
Regardless of the type of pond construction and seepage
barrier used for containing sludge, there is always the possibility of a
crack occurring in the barrier material with a resultant leachate flow.
In some areas, the local ordinances and environmental regulations
require that stringent monitoring systems be installed to signal if
there is any discharge of liquid from the disposal ponds that could
flow into the surface or ground waters. The degree of sophistication
of the monitoring systems is a function of the material to be contained,
local laws, integrity of the contractor operating the disposal pond,
potential damage to surrounding areas and inhabitants, and funds
available for instrumentation and/or construction.
Table 6-9 (Ref. 6-2) briefly tabulates the advantages
and disadvantages of a number of monitoring techniques. Two gen-
eral types of monitoring techniques that are currently being used have
been investigated: visual and soil resistivity.
6-3Z
-------
Table 6-8. POND LINER MATERIAL CHARACTERISTICS
Material
Flexible
Polyethylene
Polyvinyl chloride
Hypalon
Chlorinated
polyethylene
Petromat fabric
Butyl rubber
EPDM rubber
Polyester fiberglass
Nonflexible
Soil cement
Concrete
Clay
Asphalt concrete
G unite
Pozzolan stabilized base
Thickness,3
mil
10
10 - 20
30
30
-
30
30
65
_
-
-
-
_
-
in.
-
-
-
.
1/16 - 1/8
-
-
-
6
6
Up to 18
6
3
2 - 6
Permeability,
cm/sec
d
d
d
d
d
d
d
d
About 10"6
About 10'8
10"5 to 10'8
d
d
10"5 to 10"7
Life expec-
tancy, yr
20
20
20 +
20 +
20 +
20
20
20 +
20+
50+8
50+8
50+8
20+8
50+8
Dirt
cover"
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
Average installed0
cost, S/sq yd
0.70
1. 10 - 1.50
3.25
3.25
2. 00
2.80
4.00
4. 75
1. 00
3.75 - 4.75
1.00 - 6.00
4.00
6. 30
3. 85
Notes
e,f
e,f
e,h
e
e, f
OJ
aCommonly used
Protection from ultraviolet rays
cSee Section 7. 1
Superior to clay
Affected by wet/dry and hot/cold cycles
fSubject to s u If ate attack
^Industrial estimates not obtained
Possible breakdown due to ion exchange
To convert
from
sq yd
mil
in.
to
sq m
cm
cm
Multiply
by
0.8361
0.00254
2.54
-------
Table 6-9. POTENTIAL TECHNIQUES FOR MONITORING LIQUID SEEPAGE
FROM PONDED AREAS (SHEET 1 of 3)
Method
Evaporation
Deep wells
Shallow
observation
wells
Auger
Soil
sampling
Infiltro-
meters
Description
Pond evaporation
losses are compared
to pond inflow.
Ground water wells--
domestic or agricul-
tural. Equipment:
electrical conductivity
meter.
Shallow wells with
perforated casings,
gravel backfilled.
Possible equipment:
electrical conduc-
tivity meter.
Hand or power aug-
ered holes (usually
following soil sam-
pling). Equipment:
auger.
Soil sampling to in-
cremental depths
pending textural
changes. Equip-
ment: auger.
Plastic covered ring
infiltrometers 22.9 -
61 cm (9 - 24 in.)
diameter, double or
single, manometer
equipped. Equipment:
special driving
hammer.
Field application
Documentation required
for all ponds.
Monitoring quality for
back-up data and possi-
ble changes in quality
for nearby ponds.
Detection of lateral
water movement from
ponded areas over
restricting substrata.
Preliminary soil inves-
tigation of all ponds:
determination of seep-
age in and adjacent to
ponds.
Measurement of soil
profile moisture and its
quality in all ponds
when necessary.
Measurement and pond
infiltration both inside
and outside ponded
areas for all ponds.
Advantage
Easy to monitor.
inexpensive, low
maintenance.
Records easily
available, history
may be traced.
Quantity and quality
can be monitored.
fairly inexpensive.
low maintenance.
permanent
installation.
Quantity and quality
can be monitored,
inexpensive.
Minimum equip-
ment required.
offers wide range
of quality and
moisture
monitoring.
Fairly easy to mon-
itor, inexpensive.
no special mainte-
nance required,
permanent
Disadvantage
Indirect determination: does
not monitor actual seepage.
assumes pond evaporation to
be equal to nearest compara-
tive pond. Since pond evapo-
ration varies with depth and
size, method is subject to
error.
After-the-fact method. Wells
too far away or absent.
Suitable for monitoring water
table conditions only--unsat-
urated flow cannot be detected
Difficult to maintain, unsat-
urated flow cannot be
detected.
Expensive laboratory anal-
yses, requires repetitive
and background sampling.
Requires some expertise for
installation; chance of er-
rorsshort circuiting,
evaporation losses, and
mis measurement.
-------
Table 6-9. POTENTIAL TECHNIQUES FOR MONITORING LIQUID SEEPAGE
FROM PONDED AREAS (SHEET 2 of 3)
Method
Description
Field application
Advantage
Disadvantage
Piezometers
i
UJ
Gypsum
blocks
(Bouyoucos
blocks)
Porous
Neutron
probe
Remote
sensing
6.35 - 9. 52 mm (1/4-
3/8 in.) metal pipe;
perforated at end.
Equipment: driving
hammers, rivets,
rods, pump, tubing,
soundbell.
Unit: gypsum, nylon,
or fiberglass blocks;
plate electrode. Other
equipment: resistance
meter.
Ceramic porous suc-
tion cups. Equipment:
vacuum pumps,
lines, etc.
Neutron scattering
moisture meter: in-
cludes radioactive
source, transmission
lines, counter. Other
equipment: dummy
probe, access tubes,
etc.
Infrared photographic
detection of changes in
the radient energy
status of a discharge
area.
Detection and measure-
ment of moisture move-
ment under ponds over-
lying restricting layers.
Detection of changes in
soil moisture under all
ponds.
Detection of pond seep-
age quality in wide
moisture range for
nearly all ponds.
Detection of vertical
moving moisture fronts
under and surrounding
ponds.
Detection of changes in
the growth rate of plants
in and around a dis-
charge area as com-
pared to native areas.
Very inexpensive,
simple to install,
easy to read, no
special maintenance
or calibration re-
quired, both qual-
ity and quantity of
special zones can
be determined.
Easy to install,
easy to monitor,
very little mainte-
nance required.
Samples can be ob-
tained easily,
rather inexpensive,
low maintenance,
permanent
installation.
High reliability,
access tubes per-
manent, good for
frequent checking.
Monitor at any time
without prior no-
tice, permanent
record, interpre-
tation easily
delineated.
Measures only saturated
zones, relies on impervious
subsoil conditions, cannot
determine unsaturated flow.
Not capable of measuring
quality or quantity of seep-
age, calibration required--
low sensitivity in moist and
wet range. Subject to
deterioration.
Measures best under satu-
rated conditions--normally
measures near the available
moisture range, depth
limited.
Very elaborate and expensive,
requires special expertise,
frequent calibration, special
access holes, high mainte-
nance, does not detect qual-
ity, requires special storage
and licensing by AEC.
Expense not well established,
subject to weather, does not
tell quantity or quality of
drainage water.
-------
Table 6-9. POTENTIAL TECHNIQUES FOR MONITORING LIQUID SEEPAGE
FROM PONDED AREAS (SHEET 3 of 3)
Method
Salinity
sensors
Description
Salinity sensing de-
vice to detect dynamic
changes in salt con-
centration in the soil
profile.
Field application
Quick detection method
of changes in salt con-
centration in the soil
profile.
Advantage
Simple to set up
and operate. Quick
response to new
equilibrium
conditions.
Disadvantage
Initial expense is high. Does
not measure quantity and
individual ions.
I
co
-------
6.5.5.2 Visual
As noted in Section 6.5.5.1, the type and degree of
monitoring of the ponds depends upon a number of specific factors.
In the case of the Texasgulf, Inc. , potash facility at
Moab, Utah, which consists of 23 evaporation ponds totaling 1,618,800
sq m (400 acres), the company has taken the philosophy of monitoring
only the terrain and surrounding area near the pond site for any obvi-
ous seepage.
These ponds are lined with 0.0508 cm (20 mil) PVC,
and the facility has been operating for about 3 years. Figure 6-3
shows the key features of the ponds. The evaporation ponds do not
have any underdrainage or run-off system to collect any liquid that
might seep through the PVC liner. It was stated (Ref. 6-3) that
Texasgulf keeps a 6-in.-thick compacted cake of KCl/NaCl salt on
the bottom of the pond at all times, and they feel that this salt cake
acts as a complete barrier to the flow of any liquid. A 2-ft-thick
salt cake is also maintained along the inside slope of the pond. Texas -
gulf can pump the liquid from one pond to any other one in the event of
an emergency (e.g. , a leak in the liner). It has not yet been necessary
to do this.
The facility is located in the deep canyon country over-
looking the Colorado River. In keeping with the concept of monitoring
the surrounding area rather than the pond underdrainage, the local
streams flowing into the river are checked daily. The potash solution
is a bright white color with a long staying power on the ground, and if
there should be any leakage it shows up very fast. Small dams have
been built around all pipeline connections to and from the ponds to
retain any leakage and also at various locations at which the potash
solution could possibly flow into the streams.
There is a natural outcropping of potash in the Moab,
Utah, area near the Texasgulf facility. The company personnel
6-37
-------
reported that before the evaporation ponds were originally filled,
many detailed photographs were taken of the local area with special
emphasis directed toward these points of potash outcropping. The
photographs were legally notarized by the local pollution control dis-
trict personnel and the company's legal department. Periodically
the area is resurveyed and the results compared with the original
photographs. Thus far, there has been no noticeable change in the
area to indicate any seepage or leaking taking place. The Texasgulf
personnel emphasized that because their plant is near a national park
area, all employees are extremely cautious and do everything possi-
ble to retain the natural beauty of the landscape.
American Magnesium Company is installing five solar
ponds for a total of 424, 000 sq m (105 acres) near Gail, Texas, for
evaporating water from a high solids content magnesium salt solution.
There are no provisions for underdrainage or for any type of monitor-
ing system to signal leakage or seepage from the ponds. The dirt con-
tracting work has been completed, and a flexible lining is being in-
stalled by Staff Industries, Upper Montclair, New Jersey (Ref. 6-4).
The key features of these ponds are:
a. The five ponds range in size from 60,600 to 121,200
sq m (15 to 30 acres) and from 1. 52 to 3. 66 m (5 to
12 ft) in depth.
b. The magnesium salt solution is fed into Pond No. 1
for concentrating the solids to a certain percentage
and the effluent overflowed to Pond No. 2 for further
concentration. This process is repeated through
Pond No. 5. The effluent from each pond is con-
trolled by a circular weir that can be adjusted to the
flow rate as required. Liquid from Pond No. 5 is
pumped through a 5-in. pipeline to the magnesium
processing plant located about 7 miles away.
c. The bottom surface of the pond is lined with 0.0508
cm (20 mil) PVC; the slopes, which are graded to
a 2:1 ratio, are lined with 0.0762 cm (30 mil) CPE.
6-38
-------
d. The soil is compacted to 90 - 95 percent, and all roots,
grass, and large rocks are removed to provide a rela-
tively smooth surface for the liner.
e. A freeboard of about 1 m is planned.
f. The sludge remaining in the ponds will be mainly NaCl
plus impurities. When the sludge builds up to a pre-
determined level, it will be cleaned out, and attempts
will be made to sell it for industrial use.
The Pacific Gas and Electric Company (PG&E) (Refs. 6-5
and 6-6) also uses a visual monitoring system to determine if their
evaporation pond located at Barstow, California, is leaking. The pond
is for evaporation of coolant water blowdown for the gas compressor
coolers. A cutaway view of the pond configuration as used at this loca-
tion is shown in Figure 6-2. The sketch illustrates the "underdrainage/
flow/containment" design. The base of the pond is divided into quad-
rants sloped (contoured) to a single central down pipe. A clay liner of
20. 3 cm (8 in.) is installed over the compacted soil. Above the clay
there is a 5. 08-cm-thick (2-in.) layer of clean sand. A flexible liner
of 0. 0508 cm (20 mil) PVC is placed over the sand and the pond bottom
is topped with about 30. 5 cm (1 ft) of native soil. The clay liner pro-
jects from the compacted soil to the PVC liner at the quadrant barrier
locations. This clay barrier serves as a retaining wall if there should
be a leak; liquid should flow through the sand layer to the down pipe.
From the down pipe there is a horizontal outrigger pipe to a leak de-
tection sump. These sumps have manhole openings and are visually
inspected on a routine basis for any water accumulation. Because the
pond has been designed in such a manner as to separate the total area
into distinct quadrants, it is immediately obvious which quadrant of
the pond has sustained a leak. Appropriate repairs can then be made.
Although this technique of pond leakage monitoring was
expensive to install, PG&E personnel feel that there are no moving
parts or electrical connections to go out of order, that this concept
6-39
-------
would provide them -with a positive indication if there should be a leak,
and that it would show them exactly where the leak has occurred.
6. 5. 5. 3 Soil Resistivity
The concept of measuring soil resistivity is an ac-
cepted technique in many agricultural, construction, and geology
based industries. In applying this method to the determination of
leakage or seepage of liquid from the disposal ponds, individual
ground rods (pins) are located on a grid or patterned basis beneath
the liner (or off to the side of the pond) with insulated conductors
leading to a control room. The spacing between rods is normally
limited to about 152 m (500 ft) depending upon the soil conditions at
the pond site. A multipoint recorder selects a pair of electrodes and
records the measured conductivity between the electrodes. Upon ini-
tial system installation prior to filling the ponds with liquid, a base-
line conductivity for the soil in the pond area is determined. Anytime
the conductivity between a pair of the electrodes increases above a
preselected value, an indication is provided to notify the pond oper-
ating personnel of a possible leak.
There are two disadvantages that must be evaluated
when considering this type of leak detection system. They are:
a. There is always the possibility of a false alarm sig-
nifying a leak that has not occurred; or vice versa,
a leak may have occurred that is not registered. In
either situation, the consequences could be not only
costly but potentially disastrous.
b. Over the years the repair and maintenance on this
system could be higher than on a visual inspection
system.
6.5.5.4 Summary
It is necessary that any pond leak detection system be
evaluated thoroughly during the early design phases prior to
6-40
-------
construction. Consideration is given to major aspects of the problem,
such as: cost, maintenance, federal/state/local laws and ordinances,
and the consequences of not having a reliable detection system. Em-
phasis is placed on system reliability; if the installed system is unre-
liable, it is worse than no system at all because it gives a false sense
of security.
6.5.6 Sludge Flow to Pond Site
6. 5. 6. 1 Piping
Sludge at a temperature of less than 100°C (212°F) is
pumped from the scrubber or thickener to the disposal pond. Pump-
ing slurries at this temperature and 50 percent solids content appears
to be common practice within the mining and chemical process indus-
tries and does not require a breakthrough in technology or the develop-
ment of new equipment.
Various piping construction materials are currently
available; each material has been fabricated into pipes of many dif-
ferent sizes and wall thicknesses for pumping fluids at different pres-
sures. No attempt was made in this study to evaluate all the many
varieties of piping materials (plastic, rubber lined, steel) or sizes
potentially suitable for moving the sludge to the disposal pond. The
precise selection is the detail designer's choice based upon his local
situation.
For this study, it was assumed that a 1000 MW power
plant will require six scrubbers to accommodate all of the flue gases
coming from the boilers. It was further assumed that when the power
plant is operating at capacity and for 6400 hr/year, the sludge output
is at the rate of 218,000 metric tons (240,300 short tons) per scrubber
for a sludge of 50 percent solids (including ash). The exact pipe diam-
eter will depend upon the local head loss design conditions and the
6-41
-------
desired fluid velocity. Experience has shown that the sludge velocity
in the pipes should be about 2. 14 - 3.05 m/sec (7 - 10 fps) to prevent
any settling out of the precipitate.
6.5.6.2 Pumps
Three of the most common types of pumps available to
move the sludge to the disposal pond are: centrifugal, reciprocating
and rotary. Any one of these pumps properly designed for the specific
pumping conditions (e.g. , amount of head loss, velocity, and rate)
could perform the required function. A type readily adaptable to this
task is a rubber lined centrifugal pump now being used in high abra-
sive work in the mining industry.
6.5.6.3 Flow Measurement
Numerous flow measuring devices were investigated to
ascertain the types of instrumentation needed to determine and control
the amount of fluid flowing from the scrubber to the disposal pond. A
Parshall Flume, which operates on the principle of upstream head
buildup caused by downstream venturi restriction, appears to be suited
for this task. This head change is in turn measured by either a capac-
itance, sonic, or bubbler system and transmits a signal to a device
that produces an output signal to be integrated and recorded. The
Parshall Flume was considered a better choice for this function than
a weir design because the buildup of solids in the bottom of the chan-
nel could give an erroneous reading. The flume also has a relatively
large head change compared to flow rate change. This feature makes
the flow transmission device less critical, and furthermore, the
flume can be easily cleaned or repaired.
6.5.6.4 Pond Level and Temperature Indicators
Consideration was given to the potential need for a pond
level indicator and a temperature recording instrument. Sonically
6-42
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operated level indicators are available from many manufacturers.
This technique would work satisfactorily for this task because there
is no contact with the sludge and, therefore, no contamination
problem.
Thermocouples embedded in the sludge flow stream
can provide the means for measuring the temperature of the fluid flow-
ing into the pond. The thermocouples can be connected to an indi-
cating thermometer or to a recording device.
6.6 SLUDGE CONDITIONING
The conditioning of sludge for its environmentally sound
disposal may be performed by several techniques. The most well
developed technique is chemical fixation, and data presently exist that
allow this technique to be evaluated. Other conditioning techniques
that might be used are drying, sintering, and nonchemical additives.
In each of these other fixation methods for sludge conditioning, com-
mercial processes have been or can be developed, but little or no
research into these areas has been made by the power industry. While
none of these latter methods are included in plans for operational ap-
plications, they provide alternative disposal processes that may be
suitable for specific problem cases. The following sections describe
and discuss the various methods that are technically feasible for con-
ditioning sludge to make it suitable for disposal.
6. 6. 1 Fixation
The chemical fixation processing of power plant sludges
offers an alternative disposal method that may serve several purposes.
The processors assert that soluble trace elements become chemically
bound such that their availability to subsequent leaching is minimal or
nonexistent. As an example of the chemical bonding that fixation pro-
cessing can provide, Table 6-10 shows an analysis of the leachate ob-
tained from the Shawnee Power Plant sludge, chemically fixed by one
6-43
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Table 6-10. COMPARISON OF TRACE ELEMENTS ANALYSES
BETWEEN RAW SLUDGE AND LEACHATE FROM
THAT SLUDGE AFTER CHEMICAL CONDITIONING
BY FIXATION (REF. 6-7)
Constituents
Arsenic (As)
Cadmium (Cd)
Chlorides (Cl~)
Total Chromium (Cr)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Mercury (Hg)
Nickel (Ni)
Zinc (Zn)
Phenol (C6H5OH)
Cyanide (CN~)
Sulfate (SO4~)
TVA Shawnee
TCA limestone
raw sludge
2.2
0.30
2,000
2.8
1.5
120
26
<0. 10
3.5
16
<0.25
<0. 10
>10,000
Leachate water from
conditioned sludge
<0. 10
<0. 10
64
<0.25
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
<0. 10
400
of the processors and compared with raw sludge. Thus, the use of
chemical fixation might be an effective and convenient method for
sludge detoxification (however, further assessments are necessary to
determine long-term effects under operational conditions). In addi-
tion to chemical bonding of heavy metals, the treated material is
rendered more serviceable as a landfill material and, if properly
treated by any of the processes, it can be used as structural fill. The
disposal of a material that serves as landfill is made markedly more
simple because a much larger selection of disposal sites is available,
especially in and near densely populated areas. In comparison with a
6-44
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thixotropic sludge disposal in a pond, a chemically fixed sludge
renders a disposal basin suitable for land reclamation in the future.
In addition, if the material must be transported by truck, rail, or
sometimes even by barge, a chemically fixed material offers certain
advantages in cost and convenience.
To date, three companies have been visited that have
developed technology for chemical fixation of sludge materials:
Chemfix, Division of Environmental Sciences, Inc. , Pittsburgh,
Pennsylvania; Dravo Corporation, Pittsburgh, Pennsylvania; and
International Utilities Conversion Systems, Inc. (IUCS), Division of
International Utilities, Philadelphia, Pennsylvania. Whereas all three
processors claim to produce a material that chemically binds soluble
components, their processes and products are distinctly different. In
each case, process details and additives are considered proprietary;
the brief description of these processes presented in the following sec-
tions gives some of the fundamental differences that exist between
them. These differences are also apparent by the nature of the prod-
uct of fixation. Specifically, the Chemfix process produces a material
that has soil-like characteristics, the Dravo process produces a clay-
like material, and the IUCS process produces a material that resem-
bles low-strength concrete.
None of these processors has operational field experi-
ence with power plant sludges, but each has sufficient experience in
the fixation of sludge materials to give credence to its claims. Chem-
fix has gained wide field experience in chemical fixation of solid and
liquid wastes produced by the automotive, chemical, mining, paint,
petrochemical, steel, and metals industries. Their process can han-
dle sludges with all possible solids content. The product of their
process is a soil-like material through which rain waters can easily
and readily percolate. The Dravo Corporation process is now being
6-45
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used to establish the sludge disposal system for the lime scrubber
at the Phillips Station, Duquesne Light Company, and Dravo will pro-
cess others (see Section 6. 3). They have gained extensive laboratory
experience on sludges from various air pollution control devices that
include but are not limited to power plant sulfur dioxide scrubbers and
are now starting to gain field experience in the fixation of sulfur
sludges. This process can chemically fix sludges at various solids
contents. The IUCS process has been field tested on the sludge pro-
duced by wet scrubbing effluent gases on a lead smelter using hydrated
lime as the absorbent. This sludge has many properties similar to
power plant sludges and produces a hardened composition when chem-
ically fixed. Laboratory tests have verified the similarity of sludge
behavior between this experience and power plant sludges. Curing
requires the control of excess water and additives. The suitability
of cured material as a structural material was demonstrated at the
International Transportation Exhibit (Transpo '72) where the material
was placed and compacted as part of a 110 acre parking lot. Known
planned operations of IUCS are mentioned in Section 6. 3.
6.6.1.1 The Chemfix Fixation Processes
The Chemfix process involves the reaction of at least
two chemical components with the waste material to form chemically
and mechanically stable solids. The reaction occurs at normal, am-
bient temperatures and is not affected by temperature variations. A
series of inorganic chemicals is used that has proven stability when
in contact with the elements of the environment: soil, water, air,
micro-organisms and sunlight. The particular chemical choice, chem-
ical ratios, and reagent quantities depend on the type of waste, required
speed of reaction, and the end use of the fixed material. Either reac-
tive or nonreactive wastes can be treated with the Chemfix process.
The reaction process involves a gelation state followed by a hardening
6-46
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period. Controlling the gelation time is a factor that depends on the
distance the treated material must be pumped to the disposal site.
The treated waste can be made either hard or soft with
varying textures depending on its ultimate disposal. The chemical
system reacts with all polyvalent metal ions producing stable, insolu-
ble, inorganic compounds. The resulting material can be used as
landfill and when properly nourished, grasses and plant life will
readily thrive.
6.6.1.2 The Dravo Fixation Process
The Dravo process chemically fixes sludge by the in-
clusion of a proprietary admixture called Calcilox. The additive is
mixed with the sludge usually by feeding through a pumping system
while being pumped to a disposal basin. The solids fraction of the
sludge is allowed to settle (probably with the aid of a flocculating
agent) and curing takes place over a 30-day period. Excess sludge
liquor is provided over the curing material during this time. After
curing, these liquor waters can be recirculated to the scrubbing sys-
tem, and the solids can be removed to a permanent disposal site.
Alternatively, the material can be cured in the permanent disposal
basin.
The result of the Dravo process is a fixed sludge made
firm and convenient for disposal. By adding 3 percent Calcilox (based
on sludge solids) the conditioned sludge has properties that compare
with silty clay with water permeation of 2 X 10" cm/sec; the stiffness
as determined by compressive yield is much like clay, but it does not
have the cohesiveness as determined by shear strength, and it is stable
on a 35-45 deg slope. However, more clay-like properties like
remaining stable on steeper slopes, lower permeability, and greater
stiffness are now being obtained with Calcilox additions of 5 percent.
6-47
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6.6.1.3 The IUCS Fixation Process
The IUCS process uses fly ash and a lime additive as
ingredients in their chemical fixation of sulfite/sulfate sludges. The
quantity of either of these additives depends on the water content of
the sludge and the reactivity of the fly ash. In most cases, some
amount of dewatering of the sludge is necessary for the desired reac-
tions to take place at economical amounts of the additive. The tech-
nology is best applied to lime-scrubbed sludge because reactions are
most favored by the high pH. Three primary reactions take place:
(a) the reaction of lime with soluble sulfate that originates in either
the fly ash or sludge water so as to form calcium sulfate (sulfite also
works, but the reaction takes longer), (b) the reaction of lime, sul-
fate, and iron or aluminum oxide present in the fly ash glass forms
complex sulfoferrites or sulfoaluminates (this reaction results in the
formation of the crystalline phase ettringite that contains substantial
quantities of water within the crystalline structure), and (c) the reaction
of lime with the glassy silica of fly ash results in the well-known poz-
zolanic reaction that proceeds slowly to form calcium silicate,
tobermorite.
The result of this process is a material that can develop
strengths as much as 300 psi in 7 days and greater than 1000 psi after
1 month. Falling head permeability shows that leaching of this mate-
rial during the first week of curing changes from 10 to 10" cm/sec.
The low permeability is a consequence partly of the expansive nature
of ettringite which tightly seals the set mass and prevents shrinkage
crack formation that may otherwise allow some leakage. Besides low
leach rate, the water quality of the leach rate has a reduced quantity
of trace elements approximating two orders of magnitude. Thus, as a
consequence of chemically combining trace elements into new crystal-
line phases and the reduction in leaching rate, a total reduction of
6-48
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soluble salts or toxic contaminants that are available to ground waters
can be reduced by about 10,000 times over sludge not fixed by this
process. Moreover, the application of this material in embankment-
type structures results in preferential run-off rather than permeation,
and further reduces the toxic hazard relative to ponding. An addi-
tional application for the fixed sludge is the manufacture of synthetic
aggregate that has properties suitable for usage in concrete.
6. 6. 2 Drying
An alternative method of sludge conditioning for dis-
posal might use drying of the sludge so that a solid material is dis-
posed of. By drying a sludge, many of the problems associated with
sludge are avoided and ultimate disposal can proceed by using tech-
niques developed for sanitary landfill. Moreover, in some localities,
disposal in such landfill sites would be acceptable. The Koch drier is
one of the commercial machines designed for sludge drying that are
available for this process technique. A major difficulty with the dried
sludge is based on its ability to reabsorb water. To alleviate this prob-
lem, disposal by using a fill and bank technique might be used. The
problems that could arise by leaching toxic components from the dried
sludge are avoidable by designing run-off ways such that rain waters
are not available to rejuvenate the ground waters by passing through
the disposal site. Further assessments will be made of this.
6.6.3 Sintering
Although no specific technological development has
demonstrated its feasibility, sintering of the sludge offers another
alternative method of disposal. It is presumed here that this method
of disposal would be performed not solely for the sake of disposal but
rather because of useful product results from the sintering operation.
These products might be finished products such as bricks or blocks
but more likely they would be synthetic raw material like aggregate
6-49
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for concrete or feed for cement clinker. The latter is a prime
consideration because the sludge can provide not only the lime origi-
nating from the sorbent, but also the argillaceous components for
cement originating from the fly ash. Such a sintering process will
require a subsequent scrubbing system for sulfur removal. The con-
centration of sulfur dioxide in the effluent gas would be high enough
that an efficient sulfur dioxide recovery plant can be installed to eco-
nomically make sulfuric acid or elemental sulfur. The unique market-
ing conditions necessary to make this use of sludge economically fea-
sible will limit its application to single, isolated locations.
6.6.4 Nonchemical Additives
The alternative method of sludge disposal using non-
chemical additives is an alteration of the ponding/landfill concept. In
this method, low-cost materials, such as sand, soil, or clay, are
mixed with the sludge that is disposed of by being placed in a disposal
basin. The role of these additives is primarily to dewater the sludge,
but additional utility is derived if clay is the additive. Clay has a high
ion exchange capacity and when intimately mixed with the sludge could
reduce the availability of toxic elements to subsequent leaching waters.
The superb water absorptive capability of sands and slit and the ion
exchange capacity of clay make most soils ideal additives for this dis-
posal technique.
6.6.5 Sludge Conditioning Assessment
The chemical fixation of sludge is the most advanced
conditioning technique presently available for sludge disposal. It
offers one of the more secure methods for detoxification and provides
a material suitable for landfill and, in some cases, also for structural
fill. Disposal by drying or by using nonchemical additives is less
expensive, but their use is limited by the uncertainty of the toxic
6-50
-------
hazard that may be introduced. Sintering is a technique by which
sludge is converted to a saleable product and depends on favorable
market conditions to implement.
6-51
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REFERENCES
6-1. J. W. Jones, and R. D. Stern, "Waste Products from
Throwaway Flue Gas Cleaning Processes - Ecologically
Sound Treatment and Disposal," Paper presented Environ-
mental Protection Agency Flue Gas Desulfurization Sym-
posium, New Orleans, Louisiana (14-17 May 1973).
6-2. Personal Communication, W. A. Wheeler and H. C. Ellingston,
Jr. , McKittrick Mud Company, Inc. , Bakersfield, California
(October 1973).
6-3. Personal Communication, R. L. Curfman, Texasgulf, Inc.,
Moab, Utah (October 1973).
6-4. Personal Communication, C. E. Staff, Staff Industries, Inc.,
Upper Montclair, New Jersey (October 1973).
6-5. Personal Communication, C. Lee, Pacific Gas and Electric
Company, Barstow, California (October 1973).
6-6. Personal Communication, J. A. Jedlicka, Pacific Gas and
Electric Company, San Francisco, California (October 1973).
6-7. Personal Communication, Chemfix, Division of Environmental
Sciences, Inc., Pittsburgh, Pennsylvania (September 1973).
6-52
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-------
SECTION 7
ENVIRONMENTALLY SOUND DISPOSAL COST DETERMINATION
7. 1 POND LINING AND DISPOSAL COST ESTIMATES
7. 1. 1 General
The cost for constructing a sludge pond will depend not
only on the many technical details discussed in Section 6. 5, but it will
also depend upon its location. The cost for shipping the liner materials
to the site from the factory or processing center will vary with the dis-
tances traveled, and the labor cost for construction and liner installa-
tion varies with the different areas of the country. The engineering
analysis undertaken in this study considers these variations and uses
average values such that the costs presented can be considered typical,
but not necessarily specific.
Cost data were obtained from users and builders of
sludge ponds to provide as true a cost value as possible without
requiring the preparation of detailed engineering drawings for a spe-
cific configuration pond at a definitized site location.
The following ground rules or methods were used:
a. The annual operating time (hours) of the power plant is a
function'of the age of the facility (Table 7-1). Limestone
sludge without the ash added would be about half of this
annual production quantity.
7-1
-------
Table 7-1. SLUDGE PRODUCED AS A FUNCTION OF POWER
PLANT AGE AND OPERATING HOURS
Age of power
plant, yr
0 - 1
1 - 10
11-20
21 - 30
Plant operating
hours per year
at rated capacity
6400
5850
4580
3200
Sludge at 50 percent solids including
ash--annual production, tons X 10&
Metric tons
1. 305
1. 188
0.923
0. 651
Short tons
1. 438
1.315
1. 025
0. 719
f.
g-
Engineering, experimentation, or design costs for the
sludge ponds are not included.
In many of the calculations, the cost for the land is kept
separate from the initial investment to permit compari-
sons to be made of the ponding costs using various
liners. When incorporated, the land costs are assumed
to be $1000 or $5000 per acre. The higher value repre-
sents the probable maximum cost value for disposal
site land.
The annualized cost on a 30-year average basis is
defined as 18 percent of the initial capital investment
(Ref. 7-1). This value includes such items as interest,
depreciation, insurance, replacements, maintenance,
and taxe s.
Costs have not been included for the following items
and/or equipment that might be needed or installed as
part of the overall sludge disposal operations: engi-
neering costs, operating utilities, and security alarm
systems.
All costs are as of October 1973.
The ponds are located 1. 6 km (1 mile) from the power
plant and are included as a portion of a closed-loop
system.
There are six scrubbers per a 1000 MW capacity power
plant with all scrubbers operating at the same efficiency.
To compare the costs of various types of lined ponds and
to obtain total estimated ponding disposal costs, 30-year
averaging is used. Economic comparisons between
fixation and ponding processes are on the basis of first
year costs.
7-2
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7.1.2 Flexible Liners
Figure 7-1 presents a composite cost summary for the
various flexible liner materials considered in this study. The data
were obtained from either the manufacturer of the sheeting material
or the liner installation contractor (Refs. 7-2 through 7-12). The
values shown are to be considered for planning purposes only and are
typical of the range of costs that might be expected for the fabricated
panels installed at the pond sites. For this study, however, the mid-
point of the quoted price range has been used as the installed prices
that are listed in Table 7-2.
The values shown do not include any installation
(spreading) of soil over the polyethylene or PVC film that would
require it, whereas the others may not. This particular cost was
omitted to permit a direct comparison among the different materials.
The cost for adding 15. 2 to 30. 4 cm ( 6 to 12 in.) of soil was quoted
to be in the range of 4. 19 to 12. 55 i /sq m (5 to 15 I / sq yd)
(Refs. 7-2 and 7-13).
The widespread variations in liner costs have resulted
because of the inclusion of the following factors:
a. Cost of transportation from the panel manufacturer's
facility to the field site within a radius of about
1609 km (1000 miles)
b. Variations in the cost of labor to install the panels.
c. Discounts and lower unit costs for purchasing large
quantities of the sheeting materials.
Discussions with the liner installation contractors
revealed that, because of the vast quantities of material to be involved
in the sludge ponds, it is expected that the flexible liner materials
could probably be purchased and installed at the lowest cost values
indicated in Figure 7-1; however, those lower limit values were avoided
as a precautionary measure against data which may not be reliable.
7-3
-------
TO CONVERT
5
-o 4
>*
U)
^ 3
iO
8
2
1
0
FROM
- sq yd
mil
-
TO
sq m
cm
PV<
26
JO mil 7>
I PVC
<
»
nil
MULTIPLY BY
0. 8361 T
0. 00254 T
ff E ., T POLYESTER
30 mil I FIBERGLASS
T 9 65 mil
EPDM
30 mil
^
mil
(
>
T
T
BUTYL HYPALON
> ?n M 30 mil
PETROMAT
LINERS AND THICKNESS
Figure 7-1. Relative costs of flexible liners (installed)
7-4
-------
Table 7-2. FLEXIBLE LINER COST DATA MIDPOINT
PRICE RANGE VALUE--INSTALLED
Material
Polyethylene (PE)
Polyvinyl chloride (PVC)
Polyvinyl chloride (PVC)
Petromat fabric
Butyl rubber
Chlorinated polyethylene (CPE)
Hypalon
EPDM rubber
Fiberglass polyester
Thickness, mil
10
10
20
125
30
30
30
30
65
Cost, $/sq yd
0.70a
i.ioa
1.50a
2.00
2.80
3.25
3.25
4.00
4.75
Does not include soil on top of the liner at $0. 10/sq yd.
To convert
from
to
Multiply
by
sq yd
mil
sq m
cm
0.8361
0.00254
7. 1.3
Nonflexible Liners
The costs for the nonflexible liners installed in a pond
are shown in Table 7-3. These values were obtained from installation
contractors and are considered for comparative purposes only.
7. 1.3. 1 Clay
The cost for bentonite type clay was quoted from $10 to
over $>25/ton (FOB the clay processing plant) with about $20/ton as a
typical value (Refs. 7-2 and 7-13). The cost variations are a function
7-5
-------
Table 7-3. NONFLEXIBLE LINER COST DATA--INSTALLED
Material
Soil cement
Asphalt
Concrete
Pozzolan stabilized base
Gunite
Clay
Thickness, in.
6
6
6
6
3
Up to 18
Cost, $/sq yd
1.00
4.00
3.75 - 4.75
3.85
6.30
1.00 - 6.00
To convert
from
sq yd
in.
short tons
ft
acre
to
sq m
cm
metric
tons
m
sq m
Multiply
by
0. 8361
2.45
0.9072
0.3048
4046.8
of the clay quality, degree of processing, and quantity purchased. In
addition to the basic cost of the clay, unless the pond site is located
near the clay processor, there is the additional high cost for shipping
the material to the pond site. The shipping costsa are a direct function
of the mode of transportation and distance traveled.
Examples of rail shipping costs in bulk lots from clay pits in
Wyoming are:
Ship to
Buffalo, New York
Galveston, Texas
Chicago, Illinois
Los Angeles, California
Cost, ft/ton
28
21
22
28
7-6
-------
For estimating purposes the contractors suggested that a shipping
cost of $30/ton be used. This value would include transportation
costs and costs for loading and unloading the clay at the rail heads.
With the transportation cost added to the cost of the clay, the contrac-
tors recommended that processed bentonite type clay be estimated at
$50/short ton installed. The use of clay would be prohibitive as a
pond liner unless it can be found locally or used in thicknesses of
1 - 2 in.
It was reported that the projected cost for an 18-in.-
thick clay liner installed in several large ponds being constructed in
the midwest is about $6.00/sq yd. It was further stated that the local
clay was transported by truck about 30 miles from the clay pits
directly to the pond site. Therefore, to be realistic in this study, a
cost of $6. 00/sq yd installed was used as the basis for the clay liner
calculations. It must be noted, however, that if clay suitable for pond
lining is available on the pond site, the cost could be as low as $1.00/
sq yd for a comparable liner thickness if the clay could be moved into
position by merely bulldozing.
7.1.3.2 Wood and Steel
Quotations were obtained for large wood and steel tanks
and for creosote impregnated plywood panels (Refs. 7-14 and 7-15).
Because of their high cost, this study did not evaluate these materials
as a potential sludge pond liner. Values obtained are given in
Table C-9, Appendix C.
7. 1.3.3 Asphalt
During discussions with the contractors (Refs. 7-16 and
7-17), prices of $1.75 - $2. 25/0. 836 sq m (1 sq yd) were quoted for
7. 6-cm-thick (3 in.) "asphalt coatings" installed in the ponds.
However, to be consistent with the contractor's recommendations and
7-7
-------
users of ponds constructed from asphalt liners, it was decided to use
a 15. 2 cm (6 in.) liner at a cost of $4.00/0. 836 sq m (1 sq yd) installed
(see Table 7-3). This cost includes any extra grading and compaction
of the asphalt required for the ponding application that might be needed
to prevent erosion from weathering or wave action.
7.1.3.4 Soil Cement, Concrete, Gunite, and Pozzolan
The thicknesses and costs for the cement-based products
(Refs. 7-11 and 7-18 through 7-21) used in this report are as shown in
Table 7-3. Soil cement was assumed to be disked into place in a
thickness of about 6 in. Concrete was also assumed to be installed in
a 15. 2 cm (6 in.) thickness, but the Gunite was sprayed on in a 7. 6 cm
(3 in.) coating. Three inches of Gunite was selected because company
representatives indicated that Pacific Gas and Electric Company has
had high success with this thickness of Gunite for lining dam surfaces
and water canals.
Several companies have mixed appropriate quantities of
fly ash as a pozzolan together with sand, lime, aggregate, and water
to form a cementitious material for use in road beds, embankments,
and reservoirs. This material has been considered as a possible
sludge pond liner. It has been estimated that a 6-in. -thick liner could
serve as an excellent leachate barrier. Further information on
pozzolan products is given in Section C. 3. 9.
7.1.4 Engineering Costs
The detailed engineering costs for a power plant sludge
pond will depend somewhat on whether the engineering work is per-
formed by an independent engineering firm or by the company's
in-house engineering department. In the latter case it is further
influenced in the manner in which the overhead accounting charges are
applied to a project.
7-8
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If it is an in-house effort, normally overhead expenses
are not added onto the project cost. There is also the possibility that
the in-house engineering department is considered completely within
the overhead account of the company, and then the project is not
charged directly with any engineering costs.
Other variables affecting the design cost are: charges
for any study effort prior to the detailed design phase, soil borings,
experimentation to ascertain the quality and permeability of the com-
pacted native soil, and the amount of detail design data required to
be provided to each of the supporting contractors.
It is realized that the engineering phase of the pond
design must be accomplished regardless of the type of pond liner to
be used, and that corporate funds must still be made available for
this effort.
Because of the uncertainties in the variables associ-
ated with charging off the engineering and/or experimentation
expenses, and because these expenses are not directly related to
the specific type of pond liner used, no costs have been included in
this study for the engineering and related experimental work.
Any quality control laboratory testing required, on the
effluent from the scrubber or intake water to the cooling tower, is
charged against the operation of the scrubber or tower, respectively.
7.1.5 General Contractor Costs
The costs for the general contractor to construct the
ponds (Refs. 7-2 and 7-11), the access roads, and related dirt moving
tasks will depend to a large extent on the terrain, soil conditions, and
local labor market. However, an average value for a balanced cut
and fill operation to form the side walls and to compact the soil in the
pond is quoted as $0. 635 - 0. 764/cu m ($0.75 - Sl.OO/cu yd) of dirt
moved. A number of the general contractors indicated that they would
7-9
-------
install a limited amount of unpaved access reading within the $l/cu yd
cost number. Limited access road construction includes bulldozing,
grading, and compacting a road of only a few miles primarily to per-
mit the movement of earth handling equipment needed for the pond
construction.
This cost number includes all of the bulldozing, scrap-
ing, piling the soil to one side then using this soil to construct the
dikes around the ponds, compacting the pond sidewalls and bottom,
and preparing any slope roads into the ponds.
7.1.6 Ancillary Equipment
7.1.6.1 Piping and Pumping
As indicated in Section 6. 5. 6. 1, the exact size of the
pipe to handle the flow of the sludge from the scrubbers to the pond
and of the effluent from the pond will depend upon the specific design
conditions related to each pond. In this study it was assumed that the
pond was 1. 6 km (1 mile) from the power plant and that the effluent
discharge line would also be of that length. There would be six
scrubbers per 1000 MW power plant. The cost for the piping, valves,
fittings, etc. , assumed that the pipe is laid along the surface of the
ground with proper supports added, but it does not include items such
as crossing of a major road that must be ditched and repaired.
The cost for the purchase (Ref. 7-22) and installation
of nine pumps (six from the scrubbers and three return water pumps
or spares) is about $20, 000. All pumps are to be located in a single
pump house. The cost for the pump house and installation of associ-
ated utilities was estimated to be $50, 000.
7.1.6.2 Flow, Temperature, and Level Instrumentation
Sections 6. 5. 6. 3 and 6. 5. 6. 4 briefly describe the types
of instrumentation that might be installed to monitor the flow of the
7-10
-------
limestone sludge to the pond. The cost for the Parshall Flume flow
transmitter, temperature, and level indicators and the associated
instrumentation has been quoted from the instrument contractors at
about $5000 installed (Ref. 7-23). It was assumed that the instru-
mentation could be located on a single centralized control panel to
permit operation of the sludge pond facility from a single location,
such as the pump house.
7.1.6.3 Soil Resistivity
Section 6. 5 reviews some potential types of seepage
monitoring systems that might be used to determine if any pond leak-
age occurs. For this study, it was assumed that a soil resistivity
system would be used with the rods (pins) positioned on 152. 5 m
(500 ft) centers. The cost for each copper rod was estimated to be
$100 installed. An instrument to measure and record the soil
resistivity (Ref. 7-23) has been included in the system costs; the
total cost was estimated to be $15, 000 for a 888, 000 sq m (220 acre)
size pond.
7.1.7 Labor Costs
An estimate was made of the cost for operating per-
sonnel to monitor and control the total disposal pond operations; the
estimate was $80, 000/year.
7.1.8 Cost Comparisons
7.1.8.1 Initial Investment
Fifteen types of liners of different thicknesses were
investigated relative to disposal ponds capable of containing the sludge
from the scrubbing of flue gases. The costs for ponds constructed
with these liners are summarized in Table 7-4. The costs are shown
for a pond with a 3 -year production capacity and for one with a
7-11
-------
Table 7-4. LINER MATERIAL COMPARISONS
All costs are rough order of magnitude only. Dike height is 13 ft, including 3 ft freeboard.
Material
Flexible
Polyethylene (10 mil)
Polyvinyl chloride (10 mil)
Polyvinyl chloride (20 mil)
Petromat fabric (125 mil)
Butyl rubber (30 mil)
Chlorinated polyethylene (30 mil)
Hypalon (30 mil)
EPDM rubber (30 mil)
Fiberglass polyester (65 mil)
Nonflexible
Soil cement (6 in.)
Pozzolan stabilized base (6 in.)
Asphalt (6 in.)
Concrete (6 in.)
Clay (18 in.)
Gunite (3 in.)
Index of
installed
liner
costs3
1.0d
1.49d
1.98d
2.48
3.46
4.04
4.04
4.94
5.88
1.26
4.53
4.94
5.25
7.38
7.81
Sludge production capacity, years
3
Installed,
liner cost.
$X 106
0.90d
1.34d
1.78d
2.23
3. 11
3.61
3.61
4.45
5.29
1. 13
4.08
4.45
4.73
6.63
7.02
3
3
10
Initial investment
Pond cost,0
ft/acre
5,300
7,400
9,400
11, 500
15, 500
17, 800
17,800
21, 500
25,300
6,400
19,800
21, 600
22,800
31,400
33,200
Total cost,0
$X 106
1. 19
1.63
2. 07
2.52
3.40
3.91
3.91
4.74
5. 58
1.42
4.37
4.74
5.02
6.92
7. 31
Total cost,0
$X 106
3.28
4.60
5.93
7.27
9.91
11.49
11.49
13.89
16.44
3.98
12.79
13.89
14.74
20.49
21.64
I
I-*.
ro
Liner index: $/sq yd installed/0. 80
Excludes land, pond construction, and ancillary
equipment costs
Excludes land costs
Includes cost of covering liner with soil
To convert
from
to
mil
in.
acre
ft
cm
cm
sq m
m
Multiply
by
0. 00254
2. 54
4046.8
0. 3048
-------
10-year capacity. Also shown is the cost for the installed liner only
and the cost per acre based upon the 3-year capacity size pond.
Table 7 -4 also shows the relative cost for the different
liners using 10-mil-thick polyethylene as the datum base. Figure 7-2
is a graphic representation of the initial investment of total pond costs
tabulated in Table 7-4.
The ponds were configured with 3.96-m-high (13 ft)
dikes including a 0.9 m (3 ft) high freeboard. The pond bottom was
sized to be 888,000 sq m (220 acres) for the 3-year production
capacity pond and 2.71 million sq m (669 acres) for the 10-year
capacity pond.
The ratio of surface area-to-depth of pond to contain
a constant volume (acre-feet) of sludge will affect the cost of the
individual ponds. Table 7-5 shows the breakdown of initial investment
for ponds with 3.96-, 7.01-, 13. 10-m-high (13, 23, 43 ft) dikes includ-
ing a 0.9 m (3 ft) freeboard for a 3-year and a 10-year capacity pond.
The two liners selected are 20 -mil-thick polyvinyl chloride and 30-mil-
thick Hypalon. The dike construction costs increase as the height
increases; however, there is a corresponding liner material cost
decrease because of a decreasing total surface area to be covered.
It was assumed that all of the land needed to contain the
sludge during the full 30-year life of the power plant would be pur-
chased initially. However, the sludge ponds would be constructed
periodically. Land cost was estimated at $1000 and $5000/acre. The
higher value represents the probable maximum cost value for disposal
site land. The land cost decreases as the dike height increases
because of a smaller area needed for the ponds.
Figure 7-3 illustrates the variations of capital invest-
ment for the liner only, ancillary equipment, and land as a function
of dike height when a 20-mil-thick PVC liner is used and land costs
are $1000 per acre. From these curves it is evident that for each
7-13
-------
FIBERGLASS GUNITE
POLYESTER 3 in-
65 mils^ CLAY
18 in.-v
CONCRETE \ X
EPDM
RUBBER
30 mils
3 10
POND CAPACITY,
YEAR
POZZOLAN
6 in.
HYPALON
CPE 30 mils
30 mils
BUTYL
RUBBER
30 mils
PETROMAT
125 mils
SOIL
CEMENT
6 in.
~ 15 -
E
c
8 iol_
LINER MATERIALS
NOTE:
DIKE HEIGHT IS 13 ft INCLUDING 3 ft FREEBOARD.
QINCLUDES COST FOR SOIL OVER LINER.
TO CONVERT FROM FEET TO METERS MULTIPLY BY 0.3048.
Figure 7-2. Initial investment, total pond cost
7-14
-------
Table 7-5. POND INITIAL INVESTMENT COSTS
($x io6)
Cost breakdown
Pond
Dike construction
Piping /pumping
Instrumentation
Resistivity monitoring
Subtotal
PVC (20 mil) liner
installed0
Hypalon liner installed
Total
Landd
At $1000/acre
At $5000/acree
3-year capacity
Dike height, ft
13
0.199
0.076
0.005
0.015
0.295 0.295
1.776
3.608
2.071 3.903
1.660
8.300
23
0.497
0.076
0.005
0.013
0.591 0.591
0.955
1.939
1.546 2.530
0.952
4.760
43
1. 194
0.076
0.005
0.010
1.285 1.285
0. 560
1. 137
1.845 2.422
0.639
3. 195
10-year capacity
Dike height, ft
13
0.482
0.088
0.005
0.017
0.592 0.592
5.340
10.845
5.932 11.437
1.660
8. 300
23
1.224
0.088
0. 005
0.014
1.331 1.331
2.910
5. 910
4.241 7.241
0.936
4. 680
43
2.941
0.088
0.005
0.012
3.046 3.046
1.704
3.461
4.750 6.507
0. 608
3.040
-0
I
All costs are rough order of magnitude.
Side walls have 2:1 slope for 13 ft height;
2-1/2:1 for 23 and 43 ft heights
Values applicable to equivalent cost liners
Land cost for 30-year capacity
eRepresents maximum that would probably be
paid for disposal site land.
To convert
from
ft
acres
to
m
sq m
Multiply
by
0. 3048
4046. 8
-------
I
E
3
u
TOTAL INCLUDING LAND
(at $1000 per acre)
TOTAL COST WITHOUT LAND
LAND ONLY \
(at $1000 per acre)
V
ANCILLARY
EQUIPMENT
ONLY
LINER ONLY- - INSTALLED COSTS-
I I I
10
20
30
40
50
DIKE HEIGHT, ft (including 3 ft freeboard)
Notes:
Sufficient land purchased for 30-year capacity
All costs are rough order of magnitude
To convert: From To Multiply by
ft
acres
m
sq m
0.3048
4046.8
Figure 7-3.
Capital investment for 3-year capacity pond--
example for 20-mil-thick PVC liner
7-16
-------
pond concept there is an optimum point on the capital cost curve that
represents the minimum investment.
The function of the pond influences the height of the
dikes. For example, the American Magnesium Company facility at
Gail, Texas, is being built with dikes of 1. 52 - 3. 66 m (5 - 12 ft) to
provide a large surface area for water evaporation. Whereas, a
planned Northern States Power Company disposal pond in Minnesota
will not require the evaporation surface and will contain sludge to a
depth of 12. 19 m (40 ft).
7.1.8.2 Leasing Alternative
McKittrick Mud Company, Bakersfield, California, has
proposed (Ref. 7-2) an alternative concept to the need for the utility
companies to invest its capital in sludge disposal ponds. McKittrick
personnel stated that their company would build the sludge disposal
ponds and then lease them to the power plant operators. Furthermore,
McKittrick would assume all risks in any potential contamination from
pond leakage. The utility companies might then charge off the pond
lease rental fee as part of the power plant's direct annual operating
expense. This concept was not evaluated in this study, but considera-
tion will be given in a continuation of these analyses, to leasing ponds
or pond services rather than purchasing and operating ponds.
7.1.8.3 Disposal Costs
Table 7-6 shows the average 30-year disposal cost in
dollars/short ton (50 percent solids) for the installation and operation
of the sludge ponds. The ponds selected for this example have PVC or
Hypalon liners, and dike heights range from 13 to 43 ft. Land costs
have been assumed at $1000 or $5000/acre. The higher value repre-
sents the maximum that would probably be paid for disposal site land.
From this table and Figure 7-4 it can be seen that the cost for dis-
posal is a function of: land cost, liner used, and dike height.
7-17
-------
Table 7-6. AVERAGE DISPOSAL, COSTS--30 YEAR
Total land purchased for 30-year sludge capacity. Pond capacity of 22,000 acre-ft
required for 30 years of 50 percent solids sludge with ash included. About 1025
million short tons produced per year average over 30 years. Costs based on an
annual charge of 18 percent capital investment. Includes operating labor costs.
Based on 1973 dollars. About 4560 operating hours per year average over 30 years.
Liner
only
X
X
X
X
X
X
X
X
X
X
X
X
Pond Components
Ancillary
equipment
only
-
X
X
X
-
X
X
X
-
X
X
X
Land cost,
S/acre
1000
-
-
X
-
-
-
X
-
-
-
X
-
5000a
-
-
-
X
-
-
-
X
-
-
-
X
Dike
height,
ft
13
13
13
13
23
23
23
23
43
43
43
43
Polyvinyl chloride
Thickness: 20 mil
Cost: 81. 60/sq yd installed
Mills/kWh
produced
0.51
0. 59
0.66
0.92
0. 28
0.45
0.48
0. 63
0. 17
0. 53
0.55
0.66
$/ton of
sludge
2.27
2.63
2.92
4. 08
1. 25
2.00
2.14
2. 80
0.76
2.36
2.45
2.94
Hypalonb
Thickness: 20 mil
Cost: S3. 25/sq yd installed
Mills/kWh
produced
1.02
1. 10
1. 16
1.43
0.55
0.72
0.76
0.91
0.33
0. 69
0.71
0.81
S/ton of
sludge
4. 54
4. 89
5. 16
6.46
2.45
3. 20
3.38
4. 05
1.47
3. 07
3. 16
3. 60
-J
I
00
Represents maximum that would probably
be paid for disposal site land.
Values applicable to equivalent cost liners.
To convert
from
sq yd
mil
acres
short tons
to
sq m
cm
sq m
metric tons
Multiply
by
0.8361
0.00254
4046. 8
0. 9072
-------
5.0
1 I ' I ' I
PVC Thickness: 20 mil
T
4.0
-J
i
o>
3
I 3'°
I
8. 2.0
1.0
TOTAL COST
INCLUDING
LAND (at
SI000 per acre)
Cost: $1.60 per sq yd Installed.
Values applicable to equivalent
cost liners (see Figure 1-2).
aLand values represent the
maximum range ($0 to $50007
acre) that would probably be
paid for disposal site land.
TOTAL COST INCLUDI
(at $5000 per acre)a
LAND _
TOTAL COST
WITHOUT LAND" ~
LINER ONLY
INSTALLED
COST
I i I
7.0
6.0
5.0
a
at
5
s <-
S. 3.0
2.0
1.0
1 \ 'I ' I
HYPALON Thickness: 30 mil
Cost: $3.25 per sq yd Installed.
Values applicable to equivalent
cost liners (see Figure 1-2).
"Land values represent the
maximum range ($0 to S5000/
acre) that would probably be -
paid for disposal site land.
TOTAL COST INCLUDING
LAND (at $5000 per acre)"
TOTAL COST
INCLUDING
LAND (at
_$1000 per acre
LINER ONLY
INSTALLED COST
TO CONVERT:
FROM
mil
sq yd
acres
ft
short tons
$ per short ton
TO
cm
sq m
sq m
m -
metric tons
mills per kWh
MULTIPLY BY
0.00254
0. 8361
4046. 8
0.3048
0.9072
0.225
_L
J_
_L
10 20 30
DIKE HEIGHT, ft
40
SO
10 20 30
DIKE HEIGHT, ft
40
SO
Figure 7-4. Sludge disposal costsponding (30-year average)
-------
These disposal costs were calculated on the basis of
an annual average cost of 18 percent of the initial investment being
charged per year for interest, depreciation, replacement, mainte-
nance, insurance, and taxes. The annual percentage that was used
in this study was based on a generally accepted value by some power
utilities and the EPA for estimating capital charges on operating equip-
ment. Calculations were also made to determine an average cost per
kWh to dispose of the sludge by ponding during the 30-year life of the
power plant. Table 7-6 shows these values. The trends are the same
as those indicated for the disposal costs as a function of the short tons
of sludge produced.
Additional calculations were made to determine the
disposal costs during the first year that the sludge disposal pond is in
operation. The costs are in the range of $0. 51 to $2. 31/ton for a
3-year capacity pond, and $1.01 to $3. 69 for a 10-year capacity pond.
Table 7-7 presents the results of this study which was based on ponds
with PVC or Hypalon liners, pond dike heights ranging from 13 to 43 ft,
and land costs assumed to be $1000 and $5000/acre.
Data in Table 7-7 can be compared directly with the
data in Table 7-6, which shows the average cost for the sludge dis-
posal over a 30-year period. It can be seen that the first year costs
are lower than the 30-year average value because of the larger quantity
of sludge to be disposed of during the first year and a capital investment
less than the 30-year average, although the capital charges are higher
initially than the 30-year average. (For the quantities of sludge pro-
duced per year, refer to Section 7.1.1.)
7. 2 SLUDGE CONDITIONING AND DISPOSAL
COST ESTIMATES
The identification and technical descriptions of sludge
fixation (conditioning) processes that have been studied thus far are
7-20
-------
Table 7-7. SLUDGE DISPOSAL COST DURING FIRST YEAR
($/short ton of sludge)
Total land purchased for 30-year sludge capacity. Capital investment charges of
26. 5 percent first year only. The 6400 operating hours will give 1.438 million short
tons of sludge per year. Sludge contains 50 percent solids and includes ash. Labor
costs at $80, 000/year. All costs based on 1973 dollars.
Material
PVCb
20-mil thick; $1.60/sq yd
installed
Hypalonb
30-mil thick; $3.25/sq yd
installed
Land cost,
$/acre
1000
5000a
1000
5000a
3-year capacity
Dike height, ft
13
0.74
1.96
1. 08
2.31
Z3
0.52
1.22
0.70
1.40
43
0. 51
0.98
0. 62
1. 09
10-year capacity
Dike height, ft
13
1.46
2. 68
2.47
3.69
23
1.01
1.70
1.56
2.25
43
1.04
1.49
1.37
1.82
Represents maximum that would
probably be paid for disposal
site land.
Values applicable to equivalent cost
liners.
To convert
from
sq yd
acres
ft
mil
short tons
ft/short ton
to
sq m
sq m
m
cm
metric tons
mills /kWh
Multiply
by
0.8361
4046. 8
0.3048
0. 00254
0.9072
0. 225
-------
given in Section 6. 6. Cost estimates are discussed below for disposing
of chemically fixed sludge based on relevant data available from these
processes. Cost estimates vary considerably because of factors such
as the fixation processing system and contractor operating efficiencies,
sludge characteristics (e.g., water content, ash content, chemical
constituents), disposal site location and characteristics, land costs,
transportation, site monitoring, etc. Additionally, some power
companies provide their own fixation process.
Since the fixation of power plant sludges is an emerging
business, cost quotes quite often are related to the demonstration
aspect of new developments and/or the public relations benefits that
may accrue. Also, cost reductions that can be gained through process
efficiency improvements may occur as an industry grows. Therefore,
cost quotes are given as a range of values, and for the purpose of this
report they are given in general terms related to what the fixation
industry is experiencing. It is expected that -within the following year
industrial progress will have been made, and that direct charges
resulting from actual disposal operations will be available.
Documents that quote fixation disposal costs have been
reviewed. These are articles or brochures published by IUCS, Chemfix,
and Commonwealth Edison, and portions of the proceedings of the
National Power Plant Hearings in Washington, B.C., October and
November, 1973. (See Refs. 7-24 through 7-32.) Additionally, cost-
ing data have been obtained through personal communications. The
publication of fixation costs is somewhat vague, for reasons just
mentioned and because of the varying conditions that exist in the sludge
disposal operation. However, the values given tend to focus on the
general region of the costs. Comments on each are given in the
following paragraphs.
In Refs. 7-24 and 7-25, IUCS quotes the cost of con-
version of the sludge to their conditioned material--"Sulf-O-Poz."
7-22
-------
A range of $1. 50 to $2. 50/ton is given for new plants in the general
size range of 1000 to 2000 MW using lime scrubbers. This may not
include the cost of removing the Sulf-O-Poz from the plant site or all
of the necessary handling required at the disposal site.
In Refs. 7-26 and 7-27, it is reported that Chemfix,
which is currently treating industrial waste sludges, has quoted prices
of 2 to 10 cents/gal of sludge processed, and that the average is about
4 cents/gal. These values do not include the cost of removing the
material or handling it at the disposal site. Although Chemfix has not
treated power plant sludges commercially, they have shown in their
own laboratories that the Chemfix process is applicable. The cost
information given in Ref. 7-27 is not directly convertible to applica-
tions to a power plant disposal program. Early indications made in
this survey are that the Chemfix process could be used and that the
cost could be less than $5. 00/ton of sludge processed with the treated
material deposited at a nearby disposal site. Furthermore, cost
reductions may be realized through minimizing the water content of
the sludge, minimizing the pumping distances, and accounting for
large volume operations.
In Ref. 7-28, an estimate of sludge disposal costs at
Commonwealth Edison's Will County Station is given as $7. 00/ton on
a dry basis. It is assumed, though not confirmed, that this would be
approximately $3. 50/ton on a 50 percent solids basis. However, con-
tact with the author since that document was published indicates some-
what higher costs at this time. For example, recent costs of operation
have varied from $5. 25 to $10. 00/ton of sludge (50 percent solids);
the lower value is for a period in which conditions were trouble-free,
whereas the higher value is for a period during which the operation
experienced machinery breakdown and repair. In a more recent docu-
ment, Ref. 7-29, a value of $17. 10/ton on a dry basis ($8. 55 wet) is
given. These costs are for operations and maintenance only; they do
7-23
-------
not include land acquisition, pond construction, or capital equipment.
Unofficial estimates at Commonwealth Edison, considering improved
processes and reliable operations, place the projected cost of dis-
posal operations and maintenance at about $5. 00/ton (50 percent
solids).
The data from the references noted are difficult to
relate to varying water content of the sludge, chemical constituents of
the sludge, transportation and handling effects, and many other factors.
Surveys of disposal processes have included contacts with the three
companies noted and also with the Dravo Corporation in Pittsburgh,
Pennsylvania, which offers its own fixation process using their
Calcilox additive, and with the Duquesne Light Company, Pittsburgh,
Pennsylvania, which is attempting its own disposal program using
Calcilox purchased from the Dravo Corporation. A verbal report
made recently by the Dravo Corporation (Ref. 7-32) identified a total
disposal cost to the customer of $1.50 - $3. 00/ton of wet sludge. This
included pumping of the sludges as far as 10 miles from the plant site.
These values have not been published by Dravo, and any related quali-
fications have not been identified. In Ref. 7-33, the Duquesne Light
Company identified an estimated total disposal cost of their Phillips
Station lime sludge of $14. 00 - $15. 00/ton on a dry basis (approxi-
mately $7. 25 wet). This involves a fixation process, curing in a
separate basin followed by excavation and hauling to a disposal site
approximately 1 mile from the plant.
A summary of the cost data just discussed is given in
Table 7-8. Continuing surveys of these processes will be directed
toward refining these cost estimates and identifying conditions and
qualifications attached to each quote so that the existing variations
can be explained and possibly decreased, and to properly relate
disposal requirements to technology, site, and operating conditions.
7-24
-------
Table 7-8. SLUDGE FIXATION COST ESTIMATES
All values are condition and site dependent
Source
Commonwealth
Edison, Will
County Station
Duquesne Light Co.,
Phillips Station
IUCS, Inc.
Chemfix
Dravo
Quoted costs
1973,
ft/ton
11.82
17. 10
10.50
20.00
5.00
14.00 - 15.00
1. 50 - 2. 50
~5.00
1.50 - 3.00
Percent
solids
Dry
Dry
Dry
Dry
50
Dry
30 - 50
30 - 50
30 - 50
References
7-29
7-29, -30
7-31
7-31
7-31
7-33
7-24, -25
7-26
7-32
1973,
$/ton
(50 percent
solids)
5.91
8.55
5.25
10.00
5.00
7.25
1. 50 - 2. 50
~5.00
1. 50 - 3.00
Disposal conditions
On-site disposal- -vendor quote
Current estimate
Best operating experience
Worst operating experience
Company target
Total disposal
On-site disposal
On-site disposal
Total cost to customer;
includes pumping up to
10 mi
-0
I
t\>
On-site disposal; capital costs excluded
-------
It should be noted that the technology being developed
or offered by the chemical processors is or will be available to the
power industry ( see Section 6. 6). Although the processors are willing
to participate in a turnkey operation, they recommend providing a
service to the power company such that for a price the processor
will treat the material and remove it to a disposal site owned either
by the power plant or by the processor. This service can also include
the necessary monitoring of the disposal site for environmental impact.
Based on the preliminary estimates and referring to the
numerous developments and applications for sludge fixation identified
in Section 6.6, it appears that the cost of disposing of a sludge (50 per-
cent solids) in this manner ranges from approximately $1. 50 to $7. 25/
wet ton. Excluding unusual conditions it should be reasonable to narrow
this general cost range to about $2.50 to $5.00/ton for typical
operations.
The following example considers the cost of fixation/
disposal of all sludge and ash produced at a 1000 MW station using a
limestone scrubber. A total of 1. 44 million tons of 50 percent solid
sludge is produced and it is assumed that the output of the plant is
6. 4 billion kWh/year, and that the coal has a 3 percent sulfur content
and 12 percent ash. The annual cost of this form of disposal would be
0. 56 to 1.12 mills/kWh, using a disposal cost of $2. 50 and $5. 00/ton,
respectively. If a lime scrubber is used, the cost of disposal would be
from 10 to 20 percent less, principally because the tonnage would be
reduced. Also, reductions in disposal costs should be possible by:
(a) reducing the tonnage by collecting the fly ash upstream of the
scrubber and (b) reducing the water content of the sludge.
7. 3 COST COMPARISONS--PONDING AND FIXATION
Based on information provided in Section 7.2, it is
apparent that the cost of disposal of power plant sludge by fixation
is indefinite at this time because that form of sludge disposal is in
an emerging industry with little information based on actual practice
7-26
-------
by the power utilities. Similarly, the cost of disposal by lined ponding
(see Section 7.1) is indefinite but for different reasons. The art and
technology of ponding are well established, but there is little experi-
ence with power plant sludge disposal through the use of lined ponds.
There are many choices available that offer a wide range of costs with
apparently small differences in net results. Therefore, at this time,
comparisons are made by observing the ranges of values available and
making rational comparisons in light of the variations in both the
requirements and potential disposal methods.
It must be acknowledged that these two methods, which
appear to be the best currently available or now in development, do
not necessarily offer the same degree of environmentally sound dis-
posal. For example, fixation, which maybe the more expensive
process of the two, appears to offer a permanent solution, but there
is no proof that the environmental safeguards introduced by the fixa-
tion process will protect indefinitely. Whereas flexible liner ponding,
which may be the less expensive of the two, may provide safeguards
at a particular site for as long as approximately 25 years, and at that
time some as yet undefined technology may have to be applied to
provide environmental protection afterward. Whether nonflexible
liners will be adequate for longer than 25 years is not known.
The power industry, therefore, is offered the following
three general choices if environmental safety is to be achieved:
a. Fixation that may protect indefinitely and be suitable
for land reclamation, but is unproven.
b. Flexible liners that may protect for up to 20 - 25 years
but may require additional considerations for permanent
environmental protection and land reclamation.
c. Nonflexible liners that may protect for periods greater
than 25 years, but the systems are still unproven. Per-
manent environmental protection and land reclamation
may require additional considerations.
7-27
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Comparisons of fixation and lined ponding can not be
made on an equal basis since the two methods do not always offer the
same results. If the two could offer the same environmental protec-
tion indefinitely and if land reclamation is not of primary interest at
a particular disposal site, then a reasonably equal comparison could
be made.
Regardless of the many variations and differences that
exist between the two processes, both are being considered throughout
the power generating industry. Therefore, cost comparisons are in
order at this time to assist in making the differentiation between the
two, and in making the eventual determination of what the disposition
should be toward a disposal site at the time it is filled to capacity.
Table 7-9 gives the sludge disposal cost ranges for
both the fixation and the lined pond processes. Data on the fixation
process are based upon current cost quotations from contractors and
power companies undertaking this type of operation (see Section 7.2).
The values given for the ponding process are estimates of first year
costs based on ponds lined with PVC or Hypalon (see Section 7. 1). The
ponds have dikes varying from 13 to 43 ft in height, and a capacity for
10 years sludge production was selected. This is considered repre-
sentative of a practical, initial design approach. The cost of land to
accommodate the lined ponds that would be necessary to contain the
full 30-year capacity was included in the capital investment.
A review of the values in Table 7-9 indicates that the
disposal costs by the ponding process vary from $1. 00 to $3. 70/ton
depending upon the dike height, liner material used, and cost of the
land. The comparable numbers quoted for a typical fixation process as
in Section 7. 2 is $2. 50 - $5. 00/ton. Thus it appears that on a current
cost basis, ponding is approximately half the cost of the fixation
processes.
7-28
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Table 7-9. DISPOSAL COST COMPARISONS--SLUDGE INCLUDING ASH;
50 PERCENT SOLIDS
($/short ton; 1973 dollars)
Disposal site suitable for reclamation.
Soil cover not included. Current price
quotes.
Fixation
Cost,
1.50
3.00
5.00
7.Z5
Remarks
Lowest quote
Ideal conditions
Disposal site adjacent to plant
No land cost included
Maximum quote by two processors
Fly ash supplied by plant
Disposal site up to several miles
distance
Land cost included in one case
Quote by one processor
Disposal site up to 1 mile distance
Target cost for one processor
No land cost included
Total disposal cost quote by one
power company
Values applicable to equivalent cost liners.
Represents maximum that would probably
be paid for disposal site land.
.First year costs shown. Annual capital
charge 26. 5 percent first year. Ten-year
sludge production capacity pond. Thirty -
year land cost included - no residual value.
Future effort may be required for permanent
environmental protection or land reclamation.
Ponding
Cost, $
PVC liner, 20 mil thick &
1. 00 - 1.50
1. 50 - 2.70
a
Hypalon, 30 mil thick
1.40 - 2. 50
1.80 - 3.70
Remarks
Land cost at SlOOO/acre
Land cost at $5000/acreb
Land cost at $1000/acre
Land cost at $5000/acreb
To convert Multiply
from to by
short tons metric tons 0.9072
acres sq m 4046. 8
-------
The 30-year average ponding disposal costs are given
in Table 7-6. Comparable values for fixation processes are not
available at this time.
The many factors that affect the above disposal values
are discussed in Sections 7. 1 and 7. 2, and in Appendix C. All costs
are given in 1973 dollars, and fluctuations of the economy will impact
the costs of both the fixation and ponding processes. Also, any costs
associated with land reclamation or the effects of land values and
whether the land is owned by the power company, the processor, or
others, are economic considerations additional to the values shown
above.
All values given are approximations and will be refined
in succeeding efforts to include the effects of ash content and water
content of the sludge, quantities of sludge produced per kilowatt hour
based on the sulfur input and plant operating conditions, pond piping/
pumping requirements, refined capital charges, etc.
7-30
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REFERENCES
7»1. G. T. Rochelle, "Economics of Flue Gas Desulfurization, "
Paper presented Environmental Protection Agency Flue Gas
Desulfurization Symposium, New Orleans, Louisiana
(14-17 May 1973).
7-2. Personal Communication, W. A. Wheeler and H. C.
Ellingston, Jr., MeKittrick Mud Company, Inc., Bakersfield,
California (October 1973).
7-3. Personal Communication, C. E. Staff, Staff Industries,
Inc., Upper Montclair, New Jersey (October 1973).
7-4. Personal Communication, G. E. Lewis and Pond and
Reservoir Liners, 821-944-510, Goodyear Tire and Rubber
Company, Akron, Ohio (October 1973).
7-5. Personal Communication, R. J. Bennett, Phillips Petroleum
Company, Commercial Development Division, Chemical
Department, Bartlesville, Oklahoma (October 1973).
7-6. Fiber-glass Pit Liner, Anti Pollution Liner, Inc. , Odessa,
Texas (October 1973).
7-7. Chlorinated Polyethylene for Pond Liners. 301-313-72,
Dow Chemical, Midland, Michigan.
7-8. Pond, Pit Reservoir Liners of Hypalon. A70059, E. I.
Du Pont De Nemours and Company, Los Angeles, California
(October 1973).
7-9. Personal Communication, D. T. Skowlund, B. F. Goodrich,
General Products Company, Marietta, Ohio (October 1973).
7-10. Personal Communication, O. H. Hensgen, Waterproofing
Systems, Inc., Los Angeles, California (September 1973).
7-11. Personal Communication, J. A. Jedlicka, Pacific Gas and
Electric Company, San Francisco, California.
7-12. Personal Communication, C. Lee, Pacific Gas and Electric
Company, Barstow, California.
7-13. Personal Communication, D. G. Grenier, Black Hills
Bentonite Company, Mills, Wyoming (October 1973).
7-31
-------
7-14. Personal Communication, J. Evans, Buehler Tank and
Welding Works, Orange, California (October 1973).
7-15. Personal Communication, J. Langford, Pacific Wood
Tank, Water W. Perkins Company, Los Angeles, California
(October 1973).
7-16. Personal Communication, D. C. Cambell, The Asphalt
Institute, Long Beach, California (October 1973).
7-17. Personal Communication, R. Donahue, Black Top
Materials Company, Sun Valley, California (October 1973).
7-18. Personal Communication, J. A. Dobrowolski, California
Cement Company, Los Angeles, California (October 1973).
7-19. Personal Communication, E. R. Koller, Portland Cement
Association, Los Angeles, California (October 1973).
7-20. Personal Communication, D. M. Gross, Superior Gunite,
North Hollywood, California (October 1973).
7-Z1. Personal Communication, Chicago Fly Ash Company,
Chicago, Illinois (March 1973).
7-22. Personal Communication, H. Dewey, L. A. Liquid
Handling Systems, Los Angeles, California (October 1973).
7-23. Personal Communication, A. M. Beavens, Control
Specialists, Inc., El Monte, California (October 1973).
7-24. L. J. Minnick, "Fixation and Disposal of Flue Gas Waste
Products: Technical and Economic Assessment, " Paper
presented Environmental Protection Agency Flue Gas
Desulfurization Symposium, New Orleans, Louisiana
(14-17 May 1973).
7-25. International Utilities Conversion Systems, Inc. Testimony,
National Power Plant Hearings on Scrubbers, Washington,
D. C. (November 1973).
7-26. Personal Communication, Chemfix, Division of Environmental
Sciences, Inc., Pittsburgh, Pennsylvania.
7-27. "Truck Loads of Landfill from Waste Sludge, " Chemical
Week (26 January 1972).
7-32
-------
7-28. D. C. Gifford, "Sulfur in Utility Fuels, " Paper presented
Electrical World Conference, Chicago, Illinois
(25-26 October 1972).
7-29. D. C. Gifford, "Will County Unit 1 Limestone Wet Scrubber
Waste Sludge Disposal, " Paper presented Electrical World
Conference, Chicago, Illinois (30-31 October 1973).
7-30. Commonwealth Edison Company Testimony, National Power
Plant Hearings on Scrubbers, Washington, D. C.
(October 1973).
7-31. Personal Communication, Commonwealth Edison Company,
Chicago, Illinois.
7-32. Dravo Corporation, Oral presentation Electrical World
Conference, Chicago, Illinois (30-31 October 1973).
7-33. Duquesne Light Company Testimony, National Power
Plant Hearings on Scrubbers, Washington, D. C.
(October 1973).
7-33
-------
-------
SECTION 8
WATER QUALITY AND SOLID WASTE
DISPOSAL CRITERIA
8. 1 SUMMARY
The measure of what conditions constitute the
environmentally sound disposal of sludges is defined by authoritative
water quality standards and solid waste disposal ^regulations, or by
the judgment of regulatory officials when standards are nonapplicable
or nonexistent. The procedure, therefore, in the development of this
task effort has been to gather the existing standards to determine what
qualities or conditions must be prevented or controlled, and to com-
pare the criteria specified therein with the characteristics of as many
sludges as possible, including the effects of the method of disposal on
the environment. Also, regulatory officials have been contacted for
Water Quality Standards consist of four major components: (a) use
designations, (b) narrative and numerical criteria, (c) a plan of im-
plementation and enforcement and solid waste regulations defining
various types of waste materials with requirements for disposal,
and (d) an antidegradation statement.
8-1
-------
information on methods of standards application. The collection of
standards has produced documents from all states for which water
quality standards are available at this time (90 percent of all states).
Accordingly, solid waste regulations have been obtained from 20 per-
cent of the states. This collection of solid waste regulations is con-
sidered representative for an initial determination of status based on
information provided by the EPA NERC, Cincinnati. All told, the
water quality standards identify numerical criteria for the quality of
receiving interstate waters. These criteria when considered in terms
of regulations that may be applied to the qualities of sludges include
items such as heavy metals, toxic materials, total dissolved solids,
pH, and various compounds such as sulfates and chlorides.
Some excerpts from summaries of state water quality
criteria, showing variations in the approaches taken by several states,
are given in Table 8-1. Additionally, there are the U.S. Public Health
Service (USPHS) - 1962 Drinking Water Standards (Ref. 8-1) that pro-
vide concentration limits for chemical substances in a water supply.
This portion of the USPHS standards is reproduced in Table 8-2. Also,
some states have regulations concerning the quality of ground water.
For example, Illinois (Ref. 8-2) requires that underground waters that
are a present or potential source of water for public or food processes
supply shall meet the general and public and food processing water
supply standards. In general, other states, which do not have a specific
regulation concerning the quality of underground water, apply stream
or drinking water standards to the underground water for lack of more
definitive regulations. Finally, in all cases, according to EPA stan-
dards, stream dilution is not to be considered a substitute for or an
extension of, a waste treatment facility.
As for the regulation of solid waste disposal, standards
are much less specific than water quality criteria. Regulations ordi-
narily limit the disposal of toxic, hazardous, or harmful substances
8-2
-------
Table 8-1. EXAMPLES OF VARIATIONS IN STATE
WATER QUALITY STANDARDS
Illinois Public and Food Processing Water Supply
Constituents (selected) Concentration (mg/l)
Arsenic (total) 0.01
Barium 1. 0
Cadmium (total) 0. 01
Chlorides 250. 0
Iron (total) 0. 3
Lead (total) 0. 05
Manganese (total) 0.05
Mercury 0.0005
Nitrates plus Nitrites as N 10.0
Selenium (total) 0.01
Sulfates 250. 0
Total Dissolved Solids 500. 0
After Conventional Treatment USPHS Drinking Water
Standards - 1962
Underground Waters
Present or potential sources of water for public or food pro-
cessing limited to USPHS Drinking Water Standards - 1962;
owner monitoring of ponds required.
Kansas Water Supplies
USPHS Drinking Water Standards - 1962
Nevada
General practice:
Quality of discharge to surface waters at least as good as
receiving water
Ponding: Effluent treatment, or pond lining; owner monitor-
ing required; quality of seepage as good as receiving water.
Criteria being developed
8-3
-------
Table 8-2. EXCERPTS FROM UNITED STATES PUBLIC HEALTH
SERVICE DRINKING WATER STANDARDS - 1962
The following chemical substances should not be present in a
water supply in excess of the listed concentrations where, in the judg-
ment of the Reporting Agency and the Certifying Authority, other more
suitable supplies are or can be made available.
Substance Concentration (ing/liter)
Alkyl Benzene Sulfonate (ABS) 0. 5
Arsenic (As) 0. 01
Chloride (Cl) 250.0
Copper (Cu) 1.0
Carbon Chloroform Extract (CCE) 0.2
Cyanide (CN) 0.01
Iron (Fe) 0. 3
Manganese (Mn) 0.05
Nitrate (NO3) 45.0
Phenols 0.001
Sulfate (SO4) 250.0
Total Dissolved Solids 500.0
Zinc (Zn) 5.0
The presence of the following substances in excess of the con-
centrations listed shall constitute grounds for rejection of the supply.
Arsenic (As) 0. 05
Barium (Ba) 1.0
Cadmium (Cd) . 0.01
Chromium (Hexavalent) (Cr ) 0.05
Cyanide (CN) 0. 2
Lead (Pb) 0.05
Selenium (Se) 0. 01
Silver (Ag) 0.05
8-4
-------
by requiring that those materials not be disposed of on the ground,
or underground without the express approval of a designated authority
such as the State Department of Health, the State Health Commissioner,
County Health Commissioner, or the State Department of Commerce.
This survey to date indicates that those offices, when judging the dis-
posal of sludges, base their judgment on sludge quality as related to
PHS water quality criteria.
The limitations imposed on sludge disposal are further
intensified by the recent passage of legislation and the potential pas-
sage of others. For example, the Federal Water Pollution Control
Act Amendments of 1972 (Ref. 8-3) essentially require the revision
and reapproval of all state water quality standards: to change appli-
cability from interstate waters to all waters including ground waters,
to specifically prohibit or limit direct discharges of pollutants to
streams, to limit subsurface disposal, and to include Federal EPA-
prescribed criteria for specific toxic elements. Additionally, the
federal drinking water standards are being revised, and legislation
is in process to develop new limitations for the land disposal of solid
waste.
Chemical analyses conducted in this program have
shown sludge properties that make those tested unsuitable for direct
discharge into streams, and because of a lack of understanding of the
attenuation of harmful or undesirable components into soil, it is be-
lieved that disposal on the earth or in an underground cavity will be
disallowed because of the potential contamination of ground waters.
The undesirable components in the sludge that have appeared in ana-
lytical tests are total dissolved solids, sulfates, chlorides, arsenic,
mercury, lead, selenium, and other materials of lesser concentra-
tions. A typical analysis of heavy metals is given in Table 8-3.
With current water quality standards and solid waste
management regulations that prohibit sludge disposal in water and
8-5
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Table 8-3. ANALYSIS OF SAMPLES TAKEN FROM LIMESTONE
SCRUBBER AT TVA SHAWNEE STATION, PADUCAH,
KENTUCKY, 11 JULY 1973
(parts /million)a
Element
Clarifier underflow
liquor
Arsenic (As)
Beryllium (Be)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr) (total)
Copper (Cu)
Lead (Pb)
Magnesium (Mg)
Mercury (Hg)
Selenium (Se)
Zinc (Zn)
0. 2
0.01
0. 005
2500C
0. 05
0.05
O.lb
600C
0.06d
0.3b
0. 5
Equivalent to mg/liter
bExceeds USPHS Standards - 1962 (see Table 1-6)
Total dissolved solids exceed USPHS Standards -
(see Table 1-6)
Exceeds some state standards
1962
8-6
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that are being interpreted to prohibit its disposal on land without
safeguards, and with new and pending legislation that is or will be
more restrictive, it is apparent that the sludges must be disposed
of in such a manner as to prevent direct discharge to streams. It
also appears that it will be necessary to prevent leaching through the
soil to ground or surface waters. There are EPA-sponsored programs
in progress to verify effective means of impounding, chemically treat-
ing, or conditioning the sludges so that their disposal will be accom-
plished in an environmentally sound manner.
8.2 REGULATIONS
8.2.1 Water Quality Standards
In conformance with the requirements of the Water
Quality Act of 1965 which amended the Federal Water Pollution Con-
trol Act of 1956, all of the states, the District of Columbia, and the
territories of Guam, Puerto Rico, and Virgin Islands established or
:,': jf
are establishing water quality standards for interstate (including
coastal) waters. In December 1970, the responsibility for adminis-
tering the Water Quality Act of 1965 was transferred from the Secre-
tary of the Interior to the Administrator of the EPA. Most of the state
standards have now been written, and they have been accepted by the
EPA. The state standards are, therefore, the major sources of cri-
teria by which the power plant scrubber effluents are to be judged at
this time, and they deal with the quality of the receiving surface waters
before or after conventional treatment. Further, the state standards,
Significant background information for the state standards can be
found in "California Water Quality Criteria, " McKee and Wolf (Ref.
8-4); "Federal Water Quality Criteria," FWPCA, Dept. of the Inter-
ior, (Ref. 8-5); "Public Health Drinking Water Standards - 1962,"
USPHS Publication 956 (Ref. 8-1); and "Water Quality Standards and
International Development, " Agency for International Development
(Ref. 8-6).
8-7
-------
when citing criteria for domestic water supplies or for food processing,
generally repeat or refer to the USPHS Drinking Water Standards that
apply to water distribution systems.
Other legislation [e.g. , the Federal Water Pollution
Control Act Amendments of 1972 (PL92-500), generally referred to
as the "New Water Act"], has established a goal of zero pollution dis-
charge by 1985. While calling for interim guidelines and standards to
regulate pollution discharges, it establishes the applicability of two
definitions of particular interest for future consideration in sludge
studies. They are:
a. The act regulates pollution discharges to all waters
of the United States including ground waters (pre-
viously, control was only for interstate waters
including coastal waters).
b. The discharge of toxic elements is not allowed in
toxic amounts.
These provisions are particularly important because
of the inclusion of ground waters in the coverage, and the allowance
of some toxic discharge even though the Act specifies a national goal
of zero pollution discharge. Limitations, guidelines, and recommended
criteria are to be published periodically by the EPA in response to the
provisions of the Act.
Summaries of Water Quality Standards of 90 percent of
the states have been obtained. Additionally, summaries of the State
Standards have been compiled by the EPA and were issued in August
1972. The federal summaries are convenient for surveying require-
ments because they compile values for a particular category (e.g. ,
"Mercury and Heavy Metals," "Acidity/Alkalinity," etc.) for all states
in a single pamphlet. However, the status of water quality regulations
is continually changing; therefore, variations will often occur between
published summaries and the current state regulations whether in use
-------
or in the process of being published. Additionally, "no degradation
of the environment" is emphasized. A sample listing of the types of
criteria that exist is given in Table 8-4.
In actual practice, and to a great extent because of the
goals and expected limitations to be imposed in accordance with the
New Water Act, the power industry generally has chosen to operate
the scrubbers and to dispose of the sludge such that there will be no
discharge to streams and no seepage to underground waters. This
appears reasonable in light of the results of The Aerospace Corpora-
tion analyses of sludge samples to-date (see typical analysis in
Table 8-3 and discussions of sludge quality in Section 2). Those data
indicate concentrations of heavy metals in excess of the criteria de-
fined in state standards and in the USPHS-1962 Drinking Water Standards.
Additionally, those sludges contain excessive concentrations of total
dissolved solids (TDS) or sulfates or chlorides. The consensus among
our contacts is that raw sludges will not be acceptable for disposal
without safeguards even if they do not have excessive concentrations
of heavy metals because they will have excessive concentrations of
TDS or the anions just mentioned.
Closed-loop operation of the scrubber prevents dis-
charge to streams. To prevent leaching problems, plans for sludge
disposal include chemical fixation or pond linings. The goal for both
disposal approaches, fixation or lining, is zero pollution; however,
the long-term effects of these approaches have not been determined.
To verify the adequacy of the disposal, most regulatory agencies re-
quire the disposal site operator to monitor adjacent streams and the
ground water, and they will make spot checks. If any leaching does
occur, the USPHS drinking water standards will probably be used as the
limiting criteria because the effects of soil attenuation are not well
defined. Some exception to this may be taken since each disposal is
8-9
-------
Table 8-4. SELECTED STATE WATER QUALITY CRITERIA (SHEET 1 of 3)
oo
h-»
o
State
Illinois
Ohio
Material or
condition
Stream quality
where water is
withdrawn for
treatment
After conven-
tional treatment
Stream quality
where water is
withdrawn for
treatment
After conven-
tional treatment
Applicability
Public and food pro-
cessing water supply
(PWS)
PWS
PWS
PWS
Criteria (selected)
As
Ba
Cd
Chlorides
Fe
Pb
Mn
Hg
Nitrates plus
Nitrites as N
Se
Sulfates
TDS
0.01 mg/liter
1.0
0.01
250.0
0. 3
0. 05
0. 05
0.0005
10.0
0.01
250.0
500.0
USPHS Drinking Water
Standards - 1962
As
Ba
Cd
Cr (Hex)
Pb
Se
Ag
Hg
USPHS - 1962
0.05 mg/liter
0.800
0.005
0.05
0.040
0. 005
0. 001
0.0005
-------
Table 8-4. SELECTED STATE WATER QUALITY CRITERIA (SHEET 2 of 3)
State
(Federal -
Department
of Interior,
Ref. 8-5)
Alabama
Maryland
New Mexico
Arizona
Kansas
Material or
condition
Toxicity
pH
pH
pH
Dissolved oxygen
Dissolved oxygen
Applicability
PWS
Receiving waters
PWS
Receiving waters
[cold water! [warm water!
[fishery J " [fishery I
[cold water! [warm water!
[fishery 1 [fishery 1
Criteria (selected)
As
Ba
B
Cd
Chlorides
Cr (Hex)
Cu
Fe
Pb
Mn
Se
Ag
Zn
Sulfates
TDS
6. 5 - 8. 5
5.0-9.0
6.6 - 8.6
6 mg/liter
- 5
0. 05 mg/liter
1. 0
1. 0
0. 01
250. 0
0. 05
1.0
0. 3
0. 05
0.05
0.01
0.05
5. 0
250. 0
500.0
- 6 mg/liter
mg/liter
oo
i
-------
Table 8-4. SELECTED STATE WATER QUALITY CRITERIA (SHEET 3 of 3)
State
Pennsylvania
Arizona
Indiana
Florida
(Federal -
Department
of Interior,
Ref. 8-5)
Material or
condition
Dissolved oxygen
Turbidity
Turbidity
Turbidity
Radiation
Applicability
[cold water] [warm water
[fishery J " ^fishery
Warm water streams
Cold water streams
All classes
All classes
Criteria
6 mg/liter -
5 mg/liter -
(selected)
5 mg/liter daily avg;
4 mg/liter minimum
50 Jackson Turbidity Units
(JTU)
10 JTU
No visible increase
50 JTU
Gross Beta
Radium -226
Strontium -90
Tritium
1000 pc/liter
3 pc/liter
10 pc/liter
3000 pc/liter
00
I
t\J
-------
a distinct case usually different from all others, being affected by
many parameters such as sludge quality, disposal techniques, weather,
topography, soil conditions, and ground and surface water proximity
and quality. The burden of proof for those exceptions, if any, will be
on the operator of the disposal site.
8.2.2 Solid Waste Regulations
The principal controls for the disposal of solid waste
are solid waste regulations prepared by the states. Additionally, there
are literally thousands of state laws dealing with individual subjects
related in one way or another to solid waste disposal; those are listed
in Ref. 8-7. Also, there are "State Solid Waste Management Plans"
which are prepared through federal grants provided by the 1965 Solid
Waste Disposal Act (PL89-272) for the purpose of establishing policies
and procedures, and to provide a base for improved solid waste legis-
lation. And in response to the Resource Recovery Act of 1970 (PL91-
512) which amended the Solid Waste Disposal Act of 1965, the EPA
Office of Solid Waste Management Programs is in the process of issu-
ing guidelines for land disposal and thermal processing operations.
Of all the documentation just mentioned, the state solid
waste regulations and the proposed EPA guidelines for land disposal
are the most appropriate for regulating sludge disposal, and then only
remotely. For example, 20 State Regulations have been reviewed in
addition to the proposed guidelines. None gives specific criteria for
the disposal of sludge; the most relevant portion of each regulation
appears to be in the definition of hazardous materials and the require-
ment of the approval of a regulatory official before dumping. A typical
example is the definition of hazardous wastes given in "Regulations of
the Virginia Department of Health Governing Disposal of Solid Waste,"
effective April 1, 1971 (Ref. 8-8): "Hazardous waste includes those
materials which, because of their inherent nature and/or quantities,
8-13
-------
require special handling during disposal to avoid creating
environmental damage or hazards to public health or safety." The
regulation goes on to say that "hazardous waste shall be disposed of
in a manner approved by the Health Commissioner." The lack of
numerical criteria apparently is due to the lack of sufficient informa-
tion to define any limits on what material can be contained by the
various soils upon which the sludges may be dumped. Contacts made
with power plant personnel and solid waste regulatory officials all
indicate that because of nonexistent criteria, the disposal of the sludge
should be made in consideration of its potential hazard to water qual-
ity, and that it should be disposed of such that seepage should not occur
to surface or ground waters. As noted in Paragraph 8. 2. 1, the gen-
eral practice to prevent seepage is to provide either an impermeable
liner in the disposal area, or a chemical fixation process. Some iso-
lated cases, as in Kansas and Alabama, are considering the disposal
of raw sludge in a pond or the disposal of dried and compacted sludge
in a pond in hopes that continued monitoring of the local ground waters
will show no appreciable degradation of the environment. The opinion
of regulatory and power plant personnel of other states, without excep-
tion, is that the disposal of sludge in that manner will not be environ-
mentally sound. The progress of those two cases will be followed dur-
ing the second half of this study.
8.2.3 Status and Plans
In consideration of existing state water quality standards
and solid waste regulations, of the Federal Water Pollution Control Act
Amendments of 1972, and of the chemical characteristics of sludges
analyzed so far in this program, it is believed that power plant sludges
must be disposed of in a manner such that seepage to surface or ground
waters will not occur. And, the prevention of seepage is considered
mandatory in the absence of data necessary to determine the attenua-
tion of leachates in soils. These statements are based on the analysis
8-14
-------
of sludges from two sites only; therefore, they cannot be considered
generally applicable at this time. Further efforts in this task will in-
clude considerations of the properties of sludges generated at other
power plants, reviews of actions taken by regulatory agencies in the
process of issuing permits for sludge disposal, and assessment of all
processes available to minimize or eliminate the undesirable qualities
of sulfur sludges.
8-15
-------
REFERENCES
8-1. "A Guide to the Interstate Carrier Water Supply
Certification Program, " 1962 Drinking Water Standards.
U. S. Public Health Service Publication 956.
8-2. Water Pollution Regulations of Illinois. State Department
of Health, Springfield, Illinois.
8-3. "Federal Water Pollution Control Act Amendments of
1972, 92nd Congress - Second Session, " United States Code
Congressional and Administrative News. No. 10, West
Publishing Company (1972).
8-4. McKee and Wolf, California Water Quality Criteria.
Publication 3-A, State Water Resources Control Board,
Sacramento, California (1971).
8-5- Federal Water Quality Criteria. Report of the National
Technical Advisory Committee to the Secretary of the
Interior, Federal Water Pollution Control Administration,
Department of the Interior, Washington, D. C. (April 1968).
8-°- Water Quality Standards and International Development.
Agency for International Development, U.S. Department of
Commerce (October 1971).
8-7. Solid Waste Laws. Autocomp Incorporated, prepared for
Environmental Protection Agency (1972).
8-8. "Regulations of the Virginia Department of Health Governing
Disposal of Solid Waste, " The Health Laws of Virginia.
1971 edition. Department of Health, Richmond, Virginia
(1 April 1971).
8-16
-------
-------
-------
SECTION 9
PROGRAM STATUS AND PLANS
9. 1 INTRODUCTION
This section presents brief summaries of the work that
has been accomplished for each task in this study and identifies the
work to be performed in the following year for each task. Most of
these statements are included in various areas of each of the preced-
ing sections; however, they are combined in this section for.
convenience.
9.2 STATUS AND PLANS
9.2.1 Chemical Analyses
Two sample sets from the TVA Shawnee Station and one
from the Mohave Station have been analyzed by various chemical tech-
niques. These analyses are not yet completed so that full chemical
characterization is not now available; however, the data to date indi-
cate that several toxic trace elements are or can be sufficiently solu-
ble to cause environmental concern in the handling and disposal of
power plant sludges.
9-1
-------
Two additional sample sets from the Shawnee limestone
scrubber will be obtained: a set from a lime eastern coal scrubber
system and a set from a double alkali eastern coal burning system.
Analyses will also be conducted on samples exposed to simulated and
environmental conditions of high oxidation potential and low pH. In
addition, analyses will be made of sludges chemically conditioned by
several different processes.
9.2.2 Toxicity Determination
Arsenic, mercury, lead, and selenium have been
identified in soluble constituents sufficient in quantity to be considered
a potential toxicity problem. Therefore, attention will be addressed
to a buildup in liquor concentrations of these elements in particular
and to other elements in the recirculation system of the Shawnee
limestone scrubber.
An explanation of the system's chemistry will be
attempted with regard to the concentration of disposed elements rela-
tive to the variables of operation. Samples from other power plants
will also be analyzed and compared with the analyses made on the
Shawnee samples.
9.2.3 Physical Properties
All physical property measurements have been made
on the Shawnee sludge and all except the completion of drainability
measurements have been made on the Mohave sludge. The physical
properties relating to sludge disposal technology will be determined
for the sludges from a lime scrubbing system and the double alkali
system.
9.2.4 Detoxification Potential
The most likely potentially toxic elements have been
identified, and several alternative methods of detoxification have been
considered in a cursory manner. Further definition of the detailed
9-2
-------
chemistry of these elements will be determined, and the various
alternative methods available for detoxification will also be further
considered. In addition, detoxification techniques for other elements
that appear to pose a toxic hazard will be assessed when the extent
of their hazard has been identified.
9. 2. 5 Disposal Methods Determination
Surveys have been made of the technology related to
potential or actual disposal methods using ponding techniques or chem-
ical fixation of the sludges. Ponding data include the use of flexible
and nonflexible liners. Fixation surveys have covered the available
technology provided by three different processors. Tentative com-
parisons have been made between the use of ponding and chemical
fixation.
Further surveys and assessments will be made of pond-
ing techniques specifically to obtain more accurate data regarding the
containment of sulfur sludges and the potential life of the liners. Con-
tact will be continued with the three chemical processors already sur-
veyed and others will be surveyed as appropriate.
9.2.6 Disposal Costs
Tentative costs have been determined for the disposal
of power plant sludges by means of using lined ponds and chemical
fixation processes. The costs are not firm and are currently given
as a range rather than in specifics.
Studies will continue for the purpose of determining
more accurate cost data for ponding and fixation. Additionally, the
effects of all pertinent variables related to costs such as coal sulfur
content, plant operating conditions, absorbent characteristics, scrub-
ber operations, fly ash collection methods, etc. , will be studied.
9-3
-------
9.2.7 Water Quality and Solid Waste Criteria
A significant number of state water quality standards
and solid waste management regulations have been obtained and re-
viewed. Sludges are generally judged against the limitations imposed
by drinking water standards, and passage of the Federal Water Pol-
lution Control Act Amendments of 1972 makes all waters of the United
States subject to environmental control. Review of these regulations
indicated that sludges must not be discharged directly into water
courses and must be contained so that they cannot leach through the
soil into ground water or surface waters.
Surveys of state water quality and solid waste regula-
tions will continue and reviews will continually be made of new guide-
lines, limitations, or regulations resulting from requirements of the
New Water Act (FWPCA - 1972). A final determination will be made
relating sludge disposal to environmental quality regulations based on
considerations of properties of sludges generated at other power
plants, reviews of actions taken by regulatory agencies in the process
of issuing permits for sludge disposal, and assessment of all processes
available to minimize or eliminate the undesirable qualities of sulfur
sludges.
9-4
-------
-------
APPENDIX A
COMPANY/AGENCY VISITS OR COMMUNICATIONS
Company /agency
Personnel contacted
Allyn Transportation Company
Los Angeles, California
Anti Pollution Liner, Inc.
Odessa, Texas
Argonaut
Division of General Motors
Detroit, Michigan
The Asphalt Institute
Long Beach, California
Bechtel Corporation
San Francisco, California
M. Lucus, Sales
Representative
G. H. Forehand, Manager
E. R. Harris, Supervisor
D. C. Campbell, District
Engineer
Satish Almaula, Scientific
Development
Dewey A. Burbank
Gene H. Dyer, Manager,
Process Development
Michael Epstein, Project
Manager
Abdul H. Saltar
Robert M. Sherwin, Scientific
Development
Louis Sybert, Scientific
Development
A-l
-------
Company/agency
Personnel contacted
Black Hills Bentonite Company
Mills, Wyoming
Black Top Materials Company
Sun Valley, California
Buehler Tank and Welding Works
Orange, California
California Cement Company
Los Angeles, California
California Institute of Technology
Pasadena, California
Chemfix, Division of Environ-
mental Sciences, Inc.
Pittsburgh, Pennsylvania
Coastal Engineering Company
Bakersfield, California
Combustion Engineering
Company, Inc.
Windsor, Connecticut
Combustion Equipment
Associates, Inc.
San Francisco, California
Commonwealth Edison Company
Chicago, Illinois
D. G. Grenier, Technical
Sales
R. Donahue, Technical
Representative
J. Evans, Technical
Representative
J. A. Dobrowolski, Manager
of Technical Services
R. H. Covell, Civil Engineer
Jack E. McKee, Professor
Environmental Engineering
Jesse R. Conner, President
Donald Opacic, Vice President
And General Manager
Lawrence P. Cowman, Vice
President
Ronald J. Poloski, Technical
Director
Robert K. Salas, Manager
Marketing Services
K. Jones, Technical
Representative
'William C. Taylor, Kreisinger
Development Laboratory
Irwin A. Raben, Vice
President
Donald C. Gifford, P. E.
Eugene B. Smyk, Chemical
Engineer
A-2
-------
Company /agency
Personnel contacted
Commonwealth Edison Company
(Continued)
Control Specialists, Inc.
El Monte, California
Dow Chemical USA
Midland, Michigan
Dravo Corporation
Pittsburgh, Pennsylvania
Duquesne Light Company
Pittsburgh, Pennsylvania
E. I. du Pont de Nemours
and Company
Los Angeles, California
Ebasco Services, Inc.
New York, New York
Ecodyne Corporation
Graver Water Division
Union, New Jersey
Christine Kondrat
Joseph Agosta
A. M. Beavens, Technical
Representative
R. B. Cramer, Technical
Representative, Olefin
Plastics Department
O. Davis, Technical Repre-
sentative, Plaquemine,
Louisiana
Mel Robinson, Vice President
William H. Lord, Projects
Director
J. G. Selmeczi, Manager of
Research
C. N. Dunn, General
Superintendent
R. G. Knight, Superintendent
of Technical Services
Robert O'Hara
Steve L. Pernick, Manager
Environmental Affairs
Department
K. Rogers, Technical Sales
Representative
John A. Rasile, P. E. , Con-
sulting Environmental
Engineer
M. Fischer, Senior Engineer
R. Parcelli, Technical
Representative
A-3
-------
Company/agency
Personnel contacted
Environmental Protection Agency
NERC, Research Triangle
Park
North Carolina
Control Systems
Laboratory
Office of Air Quality,
Planning and Standards
NERC, Cincinnati, Ohio
Solid Waste Research Lab
Advanced Waste Treatment
Research Laboratory
NERC, Corvallis, Oregon
Region 5, Chicago, Illinois
Regions 1 through 10
Everett L. Plyler, Chief, Gas
Cleaning and Metallurgical
Processes Branch
Frank T. Princiotta, Chief,
Nonregenerable Processes,
Section
Richard D. Stern, Develop-
ment Engineer (Chief, Regen-
erable Processes Section)
Julian Jones, Development
Engineer
John Williams, EPA Repre-
sentative, TVA Shawnee
Power Station
James Durham
Norbert Schomaker, Branch
Chief, Disposal Technology
Henry Johnson, Project Man-
ager, Hazardous Waste
Ron Hill, Senior Engineer
Alden G. Christiansen,
Research Sanitary Engineer
Guy R. Nelson, Research
Chemical Engineer
Chris Potos, Chief, EPA
Water Quality Standards
Offices of Water Quality and
Solid Waste; Publications;
Public Relations
A-4
-------
Company/agency
Personnel contacted
Environmental Water Control,
Inc.
Denver, Colorado
General Concrete, Ltd.
Hamilton, Ontario
General Motors Corporation
Warren, Michigan
J. H. Glenn and Associates
Vitla Park, California
B. F. Goodrich, General
Products Company
Marietta, Ohio
Goodyear Tire and Rubber
Company
Akron, Ohio
Illinois State EPA Water Quality
Standards Office
Chicago, Illinois
Industrial Resources, Inc.
Chicago, Illinois
IU Conversion Systems, Inc.
Philadelphia, Pennsylvania
B. Reetz, Technical
Representative
J. F. Boux, Chief Product
Engineer
Thomas T. Dingo, Manufac-
turing Development
James H. Frazier, Staff
Engineer
William R. Johnson,
Administrator
Robert J. Phillips, Staff
Engineer
J. Harlan Glenn
D. T. Skowlund, Marketing
Supervisor
D. Herchler
G. E. Lewis, Southern
California Technical
Representative
Carl Blomgren
Jacques M. Dulin, President
Leon V. Hirsch, President
L. J. Minnick, Executive
Vice President
Gerald Kleiman, Vice President
Richard D. Vaughan, Consultant
William J. Minnick
A-5
-------
Company /agency
Personnel contacted
Kern Rock Company
Bakersfield, California
Koch Engineering Company, Inc.
Wichita, Kansas
L. A. Liquid Handling Systems
Los Angeles, California
Louisville Gas and Electric
Louisville, Kentucky
Maness Excavating and Grading,
Inc.
Paramount, California
McKittrick Mud Company, Inc.
Bakersfield, California
National Ash Association, Inc.
Washington, D. C.
National Car Rental
Mud Cat Division
Minneapolis, Minnesota
National Lime Association
Denver, Colorado
Northern States Power Company
Minneapolis, Minnesota
Ohio Edison Company
Akron, Ohio
Ontario Hydro
Toronto, Ontario
R. Jones, General Manager
Steve Smith, Senior Project
Engineer
H. Dewey, Sales Agent
Robert P. VanNess, Manager,
Environmental Affairs
M..Haberman, Technical
Representative
W. A. Wheeler, President
H. C. Ellingston, Jr. , Vice
President
John Faber, Executive Director
D. Hallen, Western Sales
Manager
C. O'Brien, Design Engineer
Clifford J. Lewis, Environ-
mental Consultant
J. A. Noer, Mechanical
Engineer
Gary C. Ashley, Senior
Research Engineer
Richard Krueger
Neil M. Bevere, Fuel Coordi-
nation Supervisor
Lew Hartman, Surplus Sales
Engineer
A-6
-------
Company / agency
Personnel contacted
Owl Rock Products Company
Arcadia, California
Pacific Gas and Electric
Company
San Francisco, California
Walter W. Perkins Company
Los Angeles, California
Pennsylvania Department of
Environmental Resources,
Bureau of Water Quality
Assessment
Harrisburg, Pennsylvania
Phillips Asphalt Paving
Glendale, California
Phillips Petroleum Company
Bartlesville, Oklahoma
Portland Cement Association
Pacific Southwest Region
Los Angeles, California
Quelcor, Inc.
Media, Pennsylvania
J. Reece, Transportation
Agency
C. Roberts, Vice President,
Rates and Evaluation
S. M. Andrew, Manager,
Economics and Statistics
Department
J. A. Jedlicka, Senior Civil
Engineer
C. Lee, Area Gas Superin-
tendent, Hinkley Compressor
Station, Barstow, California
R. Plunkett, Superintendent,
Moss Landing Facility
J. Langford, Technical
Representative
Gary Merritt
B. Phillips, Owner
R. J. Bennett, Technical
Advisor
F. Holland, Technical Advisor
E. R. Koller, National
Accounts Executive
J. Watson Pedlow, President
A-7
-------
Company /agency
Personnel contacted
Radian Corporation
Austin, Texas
Rheem Superior Division of
Rheem Manufacturing Company
Los Angeles, California
SAS Corporation
Muscle Shoals, Alabama
Southern California Edison
Company
Rosemead, California
Stabilization Chemicals
Newport Beach, California
Staff Industries, Inc.
Upper Montclair, New Jersey
Superior Gunite
North Hollywood, California
T. E. Brown, Inc.
San Leandro, California
Tennessee Valley Authority
R. Murray Wells, Chemical
Engineer
Nancy Phillips, Chemical
Engineer
J. Lessing, Technical
Representative
A. V. Slack, President
John Norris
Alexander Wier, Jr. , Principal
Scientist for Air Quality
W. C. Craghill, General Man-
ager Soil Science Products
J. Harlan Glenn, Professional
Engineer, Consultant
T. Selfridge, Manager, Tech-
nical Operations
C. E. Staff, President
D. M. Gross, Technical
Representative
T. E. Brown, Owner
James S. Morris
J. B. Barkley
James Crowe
W. H. Elder
Neal D. Moore
Philip E. Stone
A-8
-------
Company/agency
Personnel contacted
Tennessee Valley Authority
(Continued)
Texasgulf, Inc.
Moab Potash Operations
Moab, Utah
Waterproofing Systems, Inc.
Los Angeles, California
Wisconsin Electric Power
Company
Milwaukee, Wisconsin
Colby Ardis
Gerald A. Hollinden
Robert D. Mitchell
Glendon L. Crow
R. L. Curfman, Manager
A. K. Gentry, Operations
Superintendent
O. E. Hensgen, Vice President
Merlin Abler, Sales
Coordinator
A-9
-------
-------
APPENDIX B
LABORATORY CHEMICAL ANALYSES
ANALYTICAL RESULTS
This appendix presents the analytical results of sludge
samples taken at the Shawnee and Mohave power plants. The Shawnee
(TVA) samples are from sludge produced by scrubbing flue gas from
eastern coal with a limestone sorbent. The Mohave samples are
from sludge produced by scrubbing flue gas from western coal with
a limestone sorbent.
Suitable aliquots were taken for analysis. Methods
used were emission spectroscopy (designated ES in tables of analyti-
cal results), spark source spectroscopy (SSMS), and atomic absorp-
tion (AA) spectrophotometry. Atomic absorption was the preferred
method because its greater sensitivity gives more precision and higher
accuracy. In most, if not all cases, when the AA analysis of some
elements had low sensitivity, it was still greater than that obtained
from the other analytical methods.
B-l
-------
Power plant: Shawnee
Analysis, ppm: Process Water, Make-up
Date: 1 February 1973
pH: 7.40
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
CB
Cu
F
Fe
Ga
Hg
K
LI
ES
SSMS
AA
0. 21
<0.02
<0.0005
40
<0.0005
<0.001
0.012
0.007
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
6
<0.005
10,000
38
76
12
2,500
580
1.8
AA
6
10
4
2
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Tl
V
Y
Zn
Zr
ES
29,000
110
360
<10
<100
6,500
780
<30
SSMS
>10, 000
140
4. 5
360
85
1.7
220
>10, 000
1, 500
440
15
59
AA
2
1
B-2
-------
Power plant: Shawnee
Date: 1 February 1973
Analysis, ppm: TCA Effluent, Separated,' Liquid Portion pH: 2.33
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
1.7
0.006
Z800
0.0094
0.025
0.041
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
100
0.030
0.35
Power plant: Shawnee ^ Date: 1 February 1973
Analysis, ppm: TCA Effluent, Separated, Solids Portion
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
>10.000
24
28
1,600
1,700
>10,000
47
1
33
30
MO, 000
3,700
5. 1
AA
6
2
15
14
2
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
>10.000
180
1
2,800
170
20
13
>10,000
>10,000
750
4, 500
94
63
330
AA
2
2
Liquor separated from effluent at power plant.
B-3
-------
Power plant: Shawnee Date: 1 February 1973
Analysis, ppm: TCA Effluent, Retained?" Liquid Portion pH: 7.80
Element
Al
As
B
Da
Be
Dr
C
Ca
Cd
Cl
Co
Cr
Ca
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
0.7
0.8
0.015
1600
0.0014
0.006
O.OZ1
Element
Mg
Mn
Mo
N .
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
53
0.026
0. 15
Power plant: Shawnee Date: 1 February 1973
Analysis, ppm: TCA Effluent, Retained, Solids Portion
Element
Al
As
D
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
>10,000
53
42
870
170
>10,000
79
250
1. 2
49
16
>10,000
760
7.9
AA
13
4
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
>10,000
230
3
290
150
64
30
2, 100
>10,000
1, 500
5,300
150
45
450
AA
1
16
Liquor separated from effluent after delivery at The Aerospace
Corporation.
B-4
-------
Power plant: Shawnee Date: 1 February 1973
Analysis, ppm: Clarifier Effluent, Retained^ Liquid Portion pH: 7.15
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
0. 34
1 1
1100
0.0017
0. 17
19
SSMS
AA
0. 16
0.01Z
1900
0.0039
0.015
0.051
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
67
1.6
0.56
7. 5
<0.05
14
2. 1
SSMS
AA
160
0.039
0. 54
Power plant: Shawnee Date: 1 February 1973
Analysis, ppm: Clarifier Effluent, Retained, Solids Portion
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ca
Hg
K
Li
ES
26,000
92
270,000
<10
25
5.3
2,500
27
8,800
SSMS
>10,000
16
7.6
520
140
>10,000
42
66
5.9
>10,000
860
AA
33
6
1
14
9
1
1.2
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
130
2,300
0.0017
ISO
89,000
990
5,300
SSMS
>10, 000
190
3
270
110
9
330
>10,000
1, 100
4,200
150
27
90
AA
1
2
+ Liquor separated from effluent after delivery at The Aerospace
Corporation.
B-5
-------
Power plant:
Analysis, ppm:
Shawnee
TCA Inlet Fly Ash
Date: 1 February 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Ca
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
>10,000
22
38
1,000
6.5
2,000
>10,000
25
440
1.3
25
4.2
>10,000
960
6.5
AA
32
15
6
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
y
Zn
Zr
ES
SSMS
4,400
180
5. 1
870
140
27
11
440
>10, 000
440
6,000
65
73
290
AA
3
8
Power plant:
Analysis, ppm:
Shawnee
TCA Outlet Fly Ash
Date: 1 February 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ca
Hg
K
Li
ES
SSMS
>10,000
450
2ZO
6,400
7,000
>10,000
58
230
1.4
140
30
>10,000
2,500
13
AA
50
9
11
7
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
5,700
290
230
2,800
1,800
64
40
1,200
>to,ooo
1,300
>10,000
820
47
1,600
AA
7
2
B-6
-------
Power plant: Shawnee
Analysis, pprn: Bottom Ash, Unit No. 10
Date: 1 February 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
- Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
>10, 000
3
220
>10,000
2, 500
>10, 000
17
700
6.0
220
4. 1
>IO,000
1.300
42
AA
7
10
4
2
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
9,700
530
3
350
680
63
200
>10,000
170
>10,000
290
340
640
AA
1
Power plant: Shawnee
Analysis, ppm: Coal
Date: 1 February 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Ca
Cu
F
Fe
Ca
Hg
K
Li
ES
SSMS
7,500
46
1,800
>10,000
>10,000
280
310
7.9
4, 500
3,000
3.3
AA
4
0.2
1
20
8
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
1,700
350
<30
1,700
40
30
24
>10, 000
>10, 000
1, 100
5,900
180
95
180
AA
0. 5
6
B-7
-------
Power plant: Shawnee
Analysis, ppm: Process Water, Make-up
Date: 11 July 1973
pH: 7.25
Element
Al
As
B
Ba
Be
Br
C
Ca'
Cd
Cl
Co
Cr
Ce
Cu
F
Fe
Ca
Hg
K
Li
ES
SSMS
AA
0.02
<0. OZ
0.0012
30
<0.0005
<0. 001
0.005
<0.0001
Element
Mg
Mn
Mo
N
Na
ML
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
5
<0.005
<0. 01
<0.4
Power plant: Shawnee
Analysis, ppm: Limestone
Date: 11 July 1973
Element
Al
As
B
B.a
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
7
0.6
9
2
1
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
2
2
B-8
-------
Power plant: Shawnee ^ Date: 11 July 1973
Analysis, ppm: TCA Effluent, Separated, Liquid Portion pH: 2.44
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Ca
Cu
F
Fe
Ca
Hg
K
LI
ES
SSMS
AA
1. 5
0. 020
2200
0. 0072
0.060
0. 11
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Tl
V
Y
Zn
Zr
ES
SSMS
AA
700
0.25
Power plant: Shawnee ^ Date: 11 July 1973
Analysis, ppm: TCA Effluent, Separated, Solids Portion
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Ca
Cu
F
Fe
Ca
Hg
K
LI
ES
SSMS
i
AA
2.3
8
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
17
Liquor separated from effluent at power plant.
B-9
-------
Power plant: Shawnee , Date:
Analysis, ppm: TCA Effluent, Retained, Liquid Portion
11 July 1973
pH: 8.36
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Ca
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
0.45
Z. 0
0.028
4,300
0.0092
0. 17
0.064
8
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se .
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
950
0.32
3. 1
38
Power plant: Shawnee
Analysis, ppm: TCA Effluent, Retained, Solids Portion
Date: 11 July 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
7
3
13
20
3
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
1
8
Liquor separated from effluent after delivery at The Aerospace
Corporation.
B-10
-------
Power plant: Shawnee Date: 11 July 1973
Analysis, ppm: Clarifier Effluent, Retained, Liquid Portion pH: 9.01
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Ca
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
0.30
O.OZ6
2600
0.0089
0.052
0.07
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
675
Power plant: Shawnee Date: 11 July 1973
Analysis, ppm: Clarifier Effluent, Retained, Solids Portion
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ca
Hg
K
Li
ES
SSMS
AA
33
3
18
1
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
1
4
Liquor separated from effluent after delivery at The Aerospace
Corporation.
B-ll
-------
Power plant: Shawnee
Analysis, ppm: TCA Inlet Fly Ash
Date: 11 July 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
1Z
7
4
18
2.6
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
4
7
Power plant: Shawnee
Analysis, ppm: Bottom Ash
Date: 11 July 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
AA
6
0.4
17
9
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
AA
1
7
B-12
-------
Power plant: Shawnee
Analysis, ppm: Coal
Date: 11 July 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
LI
ES
SSMS
AA
19
5
10
8
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Tl
V
Y
Zn
Zr
ES
SSMS
AA
0.3
6
B-13
-------
Power plant: Mohave Date: 30 March 1973
Analysis, ppm: Scrubber Input from Hold Tank, pH: 7. 48
Retained, Liquid Portion
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
19
300
0.30
<100
SSMS
AA
0.038
<0.001
300
0.05
0.23
0.20
Element
Mg
Mn
Mo
' N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
300
3.0
29,000
16
9.6
SSMS
AA
2,400
<0.005
0. 18
Power plant: Mohave Date:
Analysis, ppm: Scrubber Input from Hold Tank,
Retained, + Solids Portion
30 March 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ca
Hg
K
Li
ES
34, 000
< 50
250,000
71
41
12,000
<4,000
SSMS
AA
19
0.04
0.4
11
6
Element
Mg
Mn
Mo
N
Na
Nl
P
Pb
Rb
S
Se
SI
Sn
Sr
Tl
V
Y
Zn
Zr
ES
5,300
170
24,000
24
< 200
100,000
80
300
1,000
80
SSMS
AA
0.4
7
Liquor separated from effluent after delivery at The Aerospace
Corporation.
B-14
-------
Power plant: Mohave Date:
Analysis, ppm: Scrubber Slurry Effluent, Retained,"*"
Liquid Portion
30 March 1973
pH: 7.83
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ca
Hg
K
Li
ES
1.2
16
ZOO
0.37
SSMS
AA
0.03
<0.001
400
0. 1
<0.005
0.08
0.0012
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
310
3. 1
30,000
21
SSMS
AA
2,400
0.01
0.12
Power plant: Mohave Date: 30 March 1973
Analysis, ppm: Scrubber Slurry Effluent, Retained,"1" Solids Portion
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
58
28
1400
920
1600
250
53
1
190
1100
7.9
AA
21
0.07
0.6
7
10
8
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
7400
90
72
1100
22
1700
1100
42
71
AA
0.1
2
Liquor separated from effluent after delivery at The Aerospace
Corporation.
B-15
-------
Power plant: Mohave Date:
Analysis, ppm: Centrifuge Discharge, Liquid Portion
30 March 1973
pH: 6.71
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
4.0
13
180
< 2
0.82
SSMS
AA
0.028
<0.001
480
0.047
0.25
0.56
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
390
3.0
29,000
51
SSMS
AA
2,800
<0.005
0. 18
Power plant: Mohave Date: 30 March 1973
Analysis, ppm: Centrifuge Discharge, Solids Filtered
from Liquid Portion
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ca
Hg
K
Li
ES
150.000
160
1,900
42,000
43
720
360
36,000
240
9,400
SSMS
AA
44
0.05
2.5
10
30
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
13,000
460
88
52,000
140
< 5,000
640
180.000
950
9,400
300
SSMS
AA
3.2
8
B-16
-------
Power plant: Mohave
Date: 30 March 1973
Analysis, ppm: Centrifuge Discharge, Precipitate
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
46
35
2000
5500
1400
290
1
3500
2100
5.5
AA
30
0.05
0.4
17
10
6
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
5600
180
41
390
7.3
1600
3700
59
210
AA
18
Power plant: Mohave
Analysis, ppm: Process Water Make-up
Date: 30 March 1973
pH: 9.10
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
< 0.04
3.1
610
< 0.2
0.91
0.34
130
4.0
SSMS
AA
0.21
0.009
200
0.07
0.03
0.2
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
230
< 0.05
2700
41
3.7
SSMS
AA
590
0.0025
0.6
0.20
B-17
-------
Power plant: Mohave
Analysis, ppm: Process Water Make-up, Solids
Date: 30 March 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
CB
Cu
F
Fe
Ga
Hg
K
Li
ES
62,000
170
< 2.000
96.000
< 20
380
3,800
42,000
< 60
<4,000
SSMS
AA
10
0.06
2.9
5.8
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
14,000
1,300
<40
< 2.000
28
26.000
340
220,000
< 80
1,600
1,200
< 80
8,600
SSMS
AA
3.2
3
Power plant: Mohave
Analysis, ppm: Limestone
Date: 30 March 1973
Element
Al
As
B
Ba
Be
Br
C
Ca
Cd
Cl
Co
Cr
Cs
Cu
F
Fe
Ga
Hg
K
Li
ES
SSMS
3300
1 1
0.80
4.3
19
4.3
900
330
0.31
AA
5
5
0.5
14
8
2
Element
Mg
Mn
Mo
N
Na
Ni
P
Pb
Rb
S
Se
Si
Sn
Sr
Ti
V
Y
Zn
Zr
ES
SSMS
4000
150
2.2
1700
50
0.7
30
220
160
5.3
6.0
AA
5
24
B-18
-------
-------
APPENDIX C
POND LININGS AND POND CONSTRUCTION
CHARACTERISTICS AND DESIGN FEATURES
C. 1 INTRODUCTION
This appendix includes information on: (a) material
properties and characteristics of flexible and nonflexible liners, (b)
liner fabrication and installation, (c) pond design and construction,
and (d) safety.
C.2 FLEXIBLE LINER CHARACTERISTICS
C.2.1 Polyvinyl Chloride
Table C-l shows some typical properties of polyvinyl
chloride (PVC) sheeting (without scrim) as used for pond lining. This
material is used in thicknesses of 0.0254 - 0.0762 cm (10 - 30 mil)
depending upon the designer's choice. The industry (Refs. C-l through
C-3) uses 0. 0508-cm-thick (20-mil) liners because experience has
indicated that: this thickness is sufficient to resist tearing, it is less
expensive than the thicker sheetings, it is easy to handle during fac-
tory liner fabrication and field installation, and has sufficient elonga-
tion for expanding over hard points on the soil surface without tearing.
C-l
-------
Table C-l. TYPICAL PROPERTIES OF PLASTIC LINERS WITHOUT SCRIM
O
ro
Property
Specific gravity
Thickness, mil
Tensile strength, psi
Elongation, % minimum
Graves tear, Ib/in.
100% modulus, psi
Water extraction, % maximum
Volatility, %
Cold crack, °C
Dimensional stability,
% maximum (70° C)
Shore "A" durometer
Pinholes per 10 sq m
Alkali resistance
Weatherability.
Resistance to burial
Color
Vapor transmission rate
Test methods
ASTM-D-792
--
ASTM-D-882
ASTM-D-882
ASTM-D-1004
ASTM-D-882
ASTM-D-1239
ASTM-D-1203
ASTM-D-746
ASTM-D-1204
ASTM-D-676
--
CRD-572-61
--
--
ASTM-E-96-66
Range of test results
PVC
1.2-1.3
10-30
2200-2800
300-400
270-300
1000-1600
0.35
0.7-0.85
-28.9
2
65-90
<1
Pass
Good
Good
Grey-black
0. 1-0. 2
Polyethylene
0. 91-0. 95
10-30
2000-2500
500-600
--
--
<0.01C
--
<- 100
--
--
<1
__
Poor
Good
Grey-black
Chlorinated
polyethylene
1. 35-1.39
10-30
1800-2000
350-600
190-600
400-1000
0. 30
0. 30
Pass -50
3
<1
Good
Good
Grey-black
0.02
Hypalon
1. 1-1.26
30
1000-20003
250-400b
200
-45
--
-------
The PVC bonding process to be used (heat sealing or
solvent/resin) depends upon the liner manufacturer's operating pro-
cedures; however, solvent/resin bonding is used exclusively for field
installation. These joints are formed by overlapping the panel edges
by about 2. 54 - 5.08 cm (1-2 in.), and applying a solvent/resin mix-
ture as the sealing agent. A three-man crew can field seam with the
solvent/resin mixture at the rate of about 6.1 - 9. 1 m/min (20 - 30
ft/min). A typical sealer for PVC is a mixture of basic PVC resin
and tetrahydrofuran in the proper ratio to provide long shelf life and
ease of application.
Since the PVC liner material will crack or craze if it
is exposed to the ultraviolet rays of the sun for a long time, it must
be protected by at least 6 in. of soil or by some other type of ultra-
violet filter. The plastic liner material is fabricated both with and
without scrim. The scrim increases the stability and strength of the
liner and reduces its tendency to slump. Most scrims are nylon or
Dacron threads of 210 or 420 denier and have more than 8 threads/in.
Many ponds and drainage canals have been constructed
that use PVC liners. The ponds range in size from less than 2024 sq
m (1/2 acre) for small sludge or water containment ponds to large
facilities of 1,618,800 sq m (400 acres) such as the Texasgulf, Inc.
plant at Moab, Utah. The Moab facility was constructed for the evap-
oration of water from the Texasgulf potash (KC1) extraction process.
The process is used to extract KC1 from the ground by dissolving the
KC1 and NaCl in hot water and pumping the salt solution into the evap-
oration ponds. The Texasgulf ponds were lined with 0.0508 cm
(20 mil) PVC (Ref. C-4) and have been in continuous operation since
they were constructed in 1970. At this facility, PVC is used in a sin-
gle layer throughout the bottom and lower portion of the slopes. An
extra layer is used on the upper area of the side slopes to protect the
underneath sheeting; it is scheduled for replacement when visual
C-3
-------
inspection reveals that it has become brittle through exposure to
ultraviolet rays or is physically damaged. It is expected that the top
layer on the side slopes will be replaced every 4 to 5 years and that
the layer which is not exposed to the sunlight will last about 20 years.
Since winds of 30. 9 m/sec (60 knots) are common in the Moab area,
special precautions are being taken to protect the liner, such as in-
stalling heavy chain link type fencing over the exposed liner material
and weighing the fencing down with sandbags. Because of the high
winds, a freeboard of at least 0. 61 m (2 ft) is always maintained to
keep any salt solution from washing over the berm.
C.2.2 Polyethylene
Table C-l shows some typical physical properties of
polyethylene (PE) liner material (without scrim). This material is
used in thicknesses of 0.0254 - 0.0762 cm (10 - 30 mil); the thinner
material is used most often because the thicker joints are difficult to
work with. Polyethylene has been widely used for liners in water re-
tention ponds for farms, golf courses, and recreational areas. It is
less expensive than some of the other flexible liners and is readily
available throughout the country. (Refs. C-l and C-3. )
Polyethylene sheeting is purchased by the liner manu-
facturer in rolls of about 127 - 190. 5 cm (50 - 75 in. ) wide by 91.4 -
152.4m (300 - 500 ft) long. It is processed by heat sealing or
solvent/resin bonding in the factory to form the large 21.3 by 152. 4 m
(70 by 500 ft) panels.
Field installation of the PE panels is similar to other
flexible liner material, except that some fabricators prefer to use a
folded seam bond (Figure C-l) to provide a tighter seal. In addition,
an adhesive-backed tape is sometimes placed over the seal to provide
temporary added strength until the liner is covered with soil.
Polyethylene liners are normally covered with a mini-
mum of 15. 2 cm (6 in.) of soil primarily to protect the sheeting from
C-4
-------
POLYETHYLENE LINER
-ADHESIVE BACKED
TAPE
POLYETHYLENE
LINER
ADHESIVE
PLASTIC SEALER
Figure C-l. Folded seam concept
ultraviolet rays, but also to help keep the liner from floating on the
surface of the pond. The ultraviolet rays cause the film to crack or
craze with age and subsequently result in leakage. The ray's detri-
mental effect on PE liners is a major disadvantage that must always
be considered in any pond design. However, PE sheeting has been
used successfully to line agricultural ponds because the soil, which
in many cases was spread to protect the liner from farm animals that
walk into the ponds, also protected the liner against ultraviolet rays.
If the PE sheeting is protected from the ultraviolet rays, it should
last about 20 years.
Polyethylene sheeting has been used successfully in a
series of evaporation ponds of 830,000 sq m (205 acres) in Lindsay,
California. At this facility, water is evaporated from the caustic
waste of the olive processing industry. The 830,000 sq m (205 acres)
of ponds are divided into eight individual ponds ranging in area from
64,800 - 206,000 sq m (16 - 50 acres).
C-5
-------
Heat sealing sheets of chlorinated polyethylene (CPE)
to the PE sheeting is a technique that was developed by the pond liner
manufacturers to overcome the disadvantage of the ultraviolet attack.
This approach incorporates an ultraviolet resistant material for use
on the side slopes of the ponds (which are subjected to the sun's rays),
while using the PE liner on the bottom surface of the pond. The bot-
tom surface would be covered with liquid or sludge and not subjected
to the direct ultraviolet rays. However, because the PE's specific
gravity is less than 1, even if CPE is used for the side walls there
should be some method of weighting down the PE to keep it from
floating.
C.2.3 Chlorinated Polyethylene
The CPE is a flexible thermoplastic produced by the
chemical reaction of chlorine and high-density polyethylene. Table C-l
summarizes some of the typical physical properties of CPE sheeting.
Since CPE is a saturated polymer, it is reported to be relatively in-
sensitive to ozone attack. Dow Chemical (Ref. C-5) reports that CPE
samples exposed to the weather in the dry Arizona atmosphere for
7-1/2 years showed better than 90 percent retention of their original
tensile and elongation properties. The pond lining industry has con-
firmed the information that CPE is weather resistant and is not affected
by ultraviolet rays. Consequently CPE is now being widely considered
in many applications where the side slopes of the ponds have prolonged
exposure to the sun.
Although CPE is more expensive than PVC or PE, CPE
is being used to line ponds requiring long life (at least 20 years) and
resistance to certain toxic chemicals.
The CPE is fabricated into pond liners both with and
without the incorporation of scrim. The sheet thickness varies from
0.0254 - 0.0762 cm (10 - 30 mil). Goodyear Rubber (Ref. C-6) re-
ports that the 0.76 mm (30 mil) CPE liner with scrim is fabricated
C-6
-------
from two plies of 0.0355 cm (14 mil) film with the scrim sandwiched
between the films. This material is used on the side slopes of the
ponds where the added stability provided by the scrim is used to pre-
vent slumping of the plastic liner.
The large panels are fabricated in the factory by heat
sealing or resin bonding procedures, the panels are accordion folded,
brought into the field, and unfolded in place. The solvent used for
sealing CPE is normally a mixture of about 50/50 parts of toluene
and tetrahydrofuran that is mixed with CPE resin to form the bond-
ing agent. Field sealing techniques are the same as those discussed
for the PVC and PE liners.
C.2.4 Hypalon
Hypalon is a chlorosulfonated polyethylene polymer
produced by DuPont and sold to film manufacturers for calendering
into sheets about 0.0762 cm (30 mil) thick for use as pond lining. The
calendered sheets are produced in rolls 1.22 - 1.823 m (4 - 6 ft) wide
by several hundred feet long. In the liner manufacturer's factory the
large panels are formed by heat sealing or adhesive bonding the nar-
rower strips together. At the site, the accordion folded liner is un-
folded and the sealing of the large panels is accomplished by overlap-
ping 2.54 - 5.08 cm (1-2 in.) of the material and sealing the joint
with adhesive. DuPont personnel (Ref. C-7) indicated that a hot-air,
heat-welding process has also been developed for field sealing the
panels. They further stated that a process has been developed for
joining the panels together by a "zipper." The zipper is a 0.0762-cm-
thick (30 mil) Hypalon extrusion that is installed along the panel edges
when they are being fabricated. When the panels are to be connected
in the field, adhesive is injected into the tracks and the zipper is
rolled together. Trichloroethylene, which is used by many fabrica-
tors as the solvent for Hypalon, and a small amount of Hypalon resin
are sometimes used as the adhesive bonding agent.
C-7
-------
Table C-l shows some of the physical properties of
the Hypalon sheeting.
Hypalon is more expensive than the liners previously
discussed, but it is being installed because of its reported good weather-
ing characteristics, and resistance to ozone and the microorganisms
in the soil. Hypalon liners are expected to have a serviceable life of
about 20 years.
C.2.5 Butyl Rubber
Butyl rubber or isobutylene-isoprene resin that has
been calendered into sheets is used for pond lining where there are
specific requirements for resistance to highly acidic chemicals. The
properties of butyl rubber are briefly summarized in Table C-2. The
panels are joined at the site with adhesive cement or tape.
C.2.6 Ethylene-Propylene-Terpolymer Rubber
Ethylene-propylene-terpolymer (EPDM) rubber is a
synthetic rubber proposed for pond linings because it has excellent
weatherability and resistance to ozone and ultraviolet rays. Some
physical properties of EPDM rubber are shown in Table C-2. At the
present time not many ponds have been lined with this material as it
is still more expensive than many other types of flexible liners and
the annual U.S. production rate is lower. B. F. Goodrich is experi-
menting with EPDM rubber (Ref. C-8) and should be in full production
for pond liners within the next year. Currently EPDM is used as a
replacement for neoprene rubber products.
The procedures for preparing the pond site, fabricating
the large panels, and installing the liner at the pond site are generally
the same as for other types of flexible liners. In the factory, the
panels are assembled by heat sealing or adhesive bonding together
the strips of rubber sheeting. In the field, the panels are bonded
C-8
-------
with an agent reported to be a mixture of halogenated hydrocarbons
and EPDM rubber.
C.2.7 Fiberglass Mat Impregnated with Polyester Resin
Another type of liner material available for pond lining
is fiberglass matting or fabric that has been impregnated with a poly-
ester resin. This material is currently being manufactured in limited
quantities by Anti Pollution Liner, Inc. , Odessa, Texas, and has been
installed in ponds up to 8094 sq m (2 acres) (Ref. C-9).
The pond construction is the same as that previously
described for the flexible liners, except that the slopes are limited
to 3:1 or less and the anchor design on the berm is limited to Method 1
as shown in Figure 6-1. The reason for these limitations is that this
liner material is rather stiff and somewhat difficult to bend into a 90°
angle without cracking the resin/fiberglass bond. However, because
this liner material has a higher strength than the thin, flexible plastic
liners, the need to remove all sharp rocks is not as imperative. The
liner is manufactured in the factory by laying out fiberglass mats 1. 52
by 15. 2 m (5 by 50 ft) long and impregnating these mats with the poly-
ester resin. The resin has been highly catalyzed for a rapid room
temperature cure. After curing, the liner panel is rolled for delivery
to the pond site. The liner is unrolled at the site, positioned to have
about a 2. 54 - 5.08 cm (1-2 in.) overlap and stapled to the adjoin-
ing panel. Next, a 10.2 - 15.2 cm (4-6 in.) mat strip is placed
over the joint and catalyzed resin is applied to the matting to form a
rigid seal. It is reported that a crew of three or four men can install
836 - 1255 sq m (1000 - 1500 sq yd) of liner per day. The liner can be
repaired by applying a patch to the damaged area and impregnating it
with resin.
Table C-2 shows some of the physical properties of
this type of lining material.
C-9
-------
Table C-2. TYPICAL PROPERTIES OF RUBBER AND FIBERGLASS LINERS
Property
Specific gravity
Tensile strength, psi
Elongation, % minimum
Cold crack, °C
Shore "A" Durometer
Pinholes per 10 sq m
Weatherability
Flexural strength, psi at 25° C
Flexural modulus, psi at 25° C
Izod impact notched,, ft Ib/in.
Color
Thickness, mil
Test methods
ASTM-D-792
ASTM-D-412
ASTM-D-412
ASTM-D-746
ASTM-D-676
--
--
- -
--
--
--
Range of test results
Butyl
rubber
0.90-1.2
2, 500-3,000
650-850
-45
40-90
<1
Good
- -
--
--
--
EPDM
rubber
0.87-0.9
800-3, 000
200-600
-50
20-95
<1
Good
-
--
--
--
^
Fiberglass
>2.5
10, 000-14,000
--
--
--
--
--
27, 000-38,000
1.3 X 106
12-14
Marine blue
65
o
I
Fiberglass mat impregnated with polyester resin; no ASTM test method specified
To convert
from
to
Multiply
by
Ib/sq in.
ft Ib/in.
gm/sq cm
gm-m/cm
70.31
54.5
-------
C.2.8 Petromat
Petromat pond lining material is a nonwoven
polypropylene fabric coated with an asbestos filled (0. 254 cm size)
asphalt emulsion. The liner material is fabricated by producing the
lightweight fabric (169. 5 gm/sq m) (5 oz/sq yd) in rolls 4. 57 m (15 ft)
wide by 91.4 m (300 ft) long, laying this fabric strip in the pond area,
and then sewing the individual uncoated strips together. After cover-
ing the pond area with fabric, the asphalt emulsion is sprayed onto the
fabric surface. The emulsion is sprayed warm to permit it to pene-
trate the fabric, but not hot so as to run down the slide slopes.
Phillips Petroleum Company makes Petromat and has
been constructing ponds from this material for their own use since
1967 (Ref. C-10). About 242,000 sq m (60 acres) of ponding is now
in operation. The largest single pond lined with Petromat is about
72,800 sq m (18 acres).
The pond configuration and construction techniques are
the same as described previously for the plastic liners. The ground
must be compacted, all roots and large stones removed (pea size
gravel can be tolerated), and the slopes limited to 2:1 or less. If a
large area of the liner needs to be repaired, the damaged section can
easily be removed prior to sludge additions, a patch of uncoated poly-
propylene sewn in its place, and the patch sprayed with the warm
asphalt emulsion. Small areas can be repaired with a roofing adhe-
sive or mastic.
Petromat liners do not have to be covered with soil
because the asphalt is unaffected by ultraviolet rays; however, the
polypropylene is affected by the ultraviolet rays and must be coated
with the asphalt within days after installation. If it becomes neces-
sary to "dress" the liner on the side slopes, a spray coating of the
asphalt emulsion can be applied to the surface. With proper mainte-
nance and repair, Petromat liners should last over 20 years.
C-ll
-------
Table C-3 shows some of the physical characteristics
of the Petromat fabric; the asphaltic emulsion is added to this fabric.
C.3 NONFLEXIBLE LINER CHARACTERISTICS
C.3.1 Chemical Soil Sealers
Treating the soil with an emulsion of oil soluable res-
inous polymers is another sealing technique used at the sludge dis-
posal pond site. Chemical soil sealer is reported to be a mixture of
sodium polyacrylates of molecular weight over 100,000 and cross-
linked unsaturated fatty acids (such as linoleic acid) with a high degree
of double bonds (Refs. C-ll and C-12). When the sealer is mixed with
water in a ratio of 1 part sealer to 1000 parts water, the sealer pene-
trates the soil and fills in the pores thereby reducing the size of
Table C-3. TYPICAL PROPERTIES OF PETROMAT FABRIC
Property
a
Range of
test results
Tensile strength in either direction, minimum
per inch of width, Ib
Elongation, in. maximum
Warp direction, 20-lb pull
Fill direction, 50-lb pull
Weight, oz/sq yd
50
0.5
1. 1
3-5
Material is nonwoven polypropylene fabric coated with an
asbestos filled asphalt emulsion
To convert from to Multiply by
Ib
in.
oz/sq yd
gm
cm
gm/sq m
453.6
2. 54
33.9
C-12
-------
openings among the soil particles. It is reported that by proper use
of this type of material the seepage rate can be limited to 548 - 3280
liters/sq m (1. 8 - 10. 8 cu ft of water per sq ft) of wetted soil per
year. Wet/dry cycles in some soils cause stress cracking that de-
stroys the benefit of the chemical sealer, and a resealing process is
necessary. This technique has been used in water control ponds, and
has the advantage that it can be applied prior to filling the pond or
used as a repair technique after the pond has been filled.
Since chemical soil sealers have been used primarily
with drinking water and recreational ponds, information is not cur-
rently available about its reaction with the limestone sludge material.
C.3.2 Soil Cement
Soil cement has been used for lining water storage
reservoirs, irrigation and drainage channels, sewage lagoons, mill
ponds, and as slope protection for earthen dams and other embank-
ments (Ref. C-13). It consists of Portland cement, soil, and water;
proportioned, mixed, placed, and compacted so that the complete soil
cement in place forms a dense, uniform mass. Proportioning and
mixing of the soil and cement are accomplished by either the mix-in-
place or the central mixing plant method. In general, the central
plant method is more economical, except for projects requiring very
small quantities of soil cement.
Selection of soil materials and determination of cement
content are prime factors in attaining the desirable soil cement char-
acteristics (i.e., compressive strength, durability, and impermea-
bility). In general the soil should be well graded, sandy, gravelly
material. For example, in the application of soil cement for slope
protection of earthen dams it is recommended that: the soil contain
no material retained on a 5. 08 cm (2 in.) sieve, at least 55 percent
C-13
-------
of the material pass the No. 4 sieve, and between 5 and 35 percent
pass the No. 200 sieve.
The average cement content, depending on the type of
soil, may vary between 7 and 14 percent by weight. The most com-
mon type of cement used is the ASTM Type I. Water for mixing with
soil cement can be raw, treated, or sea water. The only requirement
is that the water be free from excessive amounts of alkalines, acids,
or organic matter. Sandy soil cement mixtures need about 18.95
liters (5 gal) of water per 0.836 sq m (1 sq yd) for a 15. 2 cm (6 in.)
compacted thickness. Evaporation losses may require an additional
7. 57 liters (2 gal) or more per 0. 836 sq m (1 sq yd).
It was reported that the permeability of the average
type of soil cement made with pure water is approximately 0. 305 m
(1 ft) per year [i. e. , flow rate of 0. 305 m (1 ft) per 0. 0929 sq m
(1 sq ft) per year through the material under a 0. 305 m (1 ft) head].
This rate may be decreased to approximately 15.2 cm (0. 5 ft) per
year by increasing the cement content and adjusting the type of soil
used.
On slopes of 4:1 or less, soil cement liners can be
constructed with normal road construction equipment. Apparently
with higher slopes a stair-step method is required. To move the
equipment up and down these slopes it must be attached with a cable
to additional equipment at the top of the slope. It has been estimated
that about a 6-in.-thick soil cement liner would be satisfactory for
sludge disposal ponds. Soil cement liner maintenance imposes no
unique problems and can be accomplished by available techniques.
Hairline shrinkage cracks will occur, but they will have a limited
effect on the liner's permeability. These cracks will probably in-
crease the normal seepage rate about 5 percent.
C-14
-------
The advantage of soil cement is that no rodent or weed
problems will be encountered. Also, with a soil cement liner, clean-
ing equipment can be operated within the sludge disposal ponds. The
disadvantage is that the cement is subject to attack by sulfate com-
pounds. Laboratory experimentation -with specific sludges must be
performed to determine the extent of this reaction. This reaction
can be decreased or nullified by using ASTM Type V cement or a fly
ash additive. Type V cement, which costs approximately 7 percent
more than Type I, is used principally where soils or ground waters
have a high sulfate content.
C.3.3 Concrete
Concrete, which is a controlled mix of cement, aggre-
gate and water, has been used extensively in the construction of irri-
gation canals, dams, water and sewage treatment units, etc. The
proportion of the three ingredients depends on the specific application.
With a 15. 2 cm (6 in.) liner of concrete and the proper water to cement
ratio, it was reported that the rate of seepage could be reduced to
approximately 0.304 cm (0.01 ft) per year as compared to soil cement
at 15.2 cm (0. 5 ft) per year. The application of a concrete liner on
slopes of 2:1 imposes no unique problems and can be accomplished
with existing equipment.
The problems and solutions to concrete being suscep-
tible to attack by sulfate compounds within the sludge are similar to
those of soil cement (see C. 3. 2). Some contractors suggested that
several coats of linseed oil applied to the concrete surface might pro-
vide protection from the possible chemical reaction from the sludge.
There should be no concrete damage by rodents or weeds.
C.3.4 Clay
Bentonite clay is a montmorillonite-based clay formed
by the alteration of volcanic ash. Although montmorillonite is the
C-15
-------
predominant constituent in bentonite, other clay minerals (e.g., illite
and kaolinite) and variable amounts of nonargillaceous detrital min-
erals may be present. Certain bentonites appear relatively pure;
however, the content of nonargillaceous minerals is very rarely below
10 percent. Moreover, cristobalite is frequently present in bentonites.
The type of montmorillonite clay itself varies among bentonites, either
in its lattice structure or in the nature of the exchangeable ions. Con-
sequently, the characteristics of bentonite clays vary among products
and a detailed knowledge of the properties of the specific clay to be
used in the sludge pond is essential (Refs. C-14 through C-16).
The treatment of commercial bentonite is relatively
simple and includes the following steps: mining, drying, and crush-
ing to size. After it is mined, either in open pits or underground,
the clay is transported to the treatment plant where it is crushed and
dried in a rotary dryer to reduce the moisture content from its mined
condition of about 40 percent moisture. This clay is next pulverized
to the proper size for the specific application.
At the pond site common sand/gravel handling equip-
ment can be used to apply the clay to the ground surface. Whether the
clay is disked into the soil and then compacted or merely applied to
the surface in the selected thickness depends on the local conditions
at the pond site. The thickness required to prevent seepage of the
leachate from the sludge is a function of the soil conditions at the pond
site and type of clay used. It was reported that sludge ponds have used
clay linings in thicknesses from a few inches to several feet.
Some of the disadvantages that must be considered when
evaluating the possible use of clay as a seepage barrier are:
a. The clay will crack when exposed to wet/dry cycles
and will not necessarily close again to form an effec-
tive seal when rewetted.
b. Small earth-burrowing animals have been reported
to have burrowed many underground passageways
C-16
-------
through the clay barrier and thus opened cracks for
the flow of the leachate.
c. There may be a need to cover the pond slopes to
protect the clay from erosion caused by the wave
action.
C.3.5 Wood
California redwood, Douglas fir, and other weed spe-
cies have been used extensively for liquid storage tanks for many
years. Wood tanks made of 7. 62-cm-thick (3 in.), clear, all-heart
California redwood are readily available. A disadvantage is that
these wooden free-standing tanks will dry out and become loose at
the joints if left empty. If allowed to remain this way, the tanks will
collapse. Ponds could be lined with creosote impregnated plywood
panels nailed together and the joints could be sealed with a mastic.
However, the cost is higher for these pond liners (Table C-4) than
for other acceptable materials.
C.3.6 Steel
Welded steel tanks are used in the chemical processing
industry; many of these tanks have inside coatings or liners to protect
them from corrosion. A typical tank that might be used to contain the
limestone sludge is one fabricated from 9. 53-mm-thick (3/8 in. ) low
carbon sheet steel of ASTM A283, Grade C. However, because of the
high cost of steel tanks (Table C-4) as compared to the cost of an open
sludge pond, they were eliminated from evaluation in this study.
C.3.7 Asphalt
Asphalt linings have been used for many years in the
construction of reservoirs, irrigation canals, and various types of
waste ponds. Two of the major types of asphaltic materials (Ref.
C-17) that could be considered for use as liners in sludge disposal
ponds are: asphalt concrete, and hot sprayed asphalt membranes.
C-17
-------
Table C-4. WOOD AND STEEL TANK COST ESTIMATES
Tanks (delivered
and erected)
Redwood, 3-in. -thick
material
Steel, ASTM A283,
Grade C
3/8-in. -thick
1/2-in. -thick
Diameter,
ft
42. 5
48.0
50.0
50.0
Height,
ft
20.0
20.0
20.0
20.0
Cost,
$
22,500a
25,000b
45,000b
15,000a
25,000b
35,000b
Without cover
bWith cover
To convert from
in.
ft
to
cm
m
Multiply by
2.45
0.3048
Asphalt concrete is a mixture of asphalt cement and
graded aggregate that is mixed, placed, and compacted under ele-
vated temperatures. For canals and laterals the lining is normally
constructed to thicknesses of at least 5.08 cm (2 in.), and for reser-
voirs thicknesses of over 7.62 cm (3 in.) are most generally used.
The dense graded, hot-mix asphalt concrete that would be used for
waste ponds is very similar to that used for highway surfaces. How-
ever, it would have a higher percentage of mineral filler and a higher
percentage (6. 5 - 9. 5 percent) of asphalt cement of a low penetration
C-18
-------
grade. A composition recommended by one of the contractors for a
dense sludge disposal pond lining is as follows:
Sieve size Percent passing by weight
9.52 mm (3/8 in.) 100
No. 4 65-85
No. 8 45-65
No. 30 20-36
No. 50 10-22
No. 200 3-9
Asphalt cement percent 5.8-7.8
by weight of total mix
The asphalt mixes can be placed on side slopes of 2:1
and on flat planes with conventional paving equipment. Power winches
and cables are generally used to maneuver the equipment on the side
slopes. The maximum steepness of slope that should be permitted
for various vertical heights of slope paving are as follows:
Vertical height Maximum Steepness
of slope paving Horizontal Vertical
up to 3 m (10 ft) 1-1/2 1
3 m to 6 m (20 ft) 1-3/4 1
6 m to 12 m (40 ft) 2 1
over 12 m 2-1/2 1
The hot sprayed asphalt membrane consists of a con-
tinuous layer of asphalt usually without filler or aggregate and is gen-
erally about 6. 35 mm (1/4 in.) thick. The application temperature of
the asphalt should be from 176.6° - 204. 4°C (350° - 400°F); the hot
asphalt can be applied under nearly any air or ground temperature
from 37.8°C (100°F) to below -17.8°C (O'F). The heated asphalt is
sprayed on in quantities of about 6.8 1/sq m (1-1/2 gal/sq yd) which
C-19
-------
will produce a membrane of approximately 6. 35 mm (1/4 in.) thick.
The membrane should be covered or buried by approximately 0.254
m (10 in. ) of earth to keep it from weathering and to protect it from
mechanical damage. For the application of the membrane lining to
the side slopes, the slopes should not be steeper than 2:1.
It was reported that the seepage rate for either of
these two asphalt linings is "immeasurable" when properly applied;
however, the exact amount of seepage is not known under field con-
ditions. It was further reported that asphalt-lined ponds have expe-
rienced difficulties with liquid accumulating behind the liner and caus-
ing a crack to occur in the coating. Furthermore, liner selection is
based primarily on the availability of material and equipment for a
particular site and the specific characteristics of the site.
Subgrade preparation is generally the same for either
type of asphalt lining to be used. It should be thoroughly cleaned of
all organic and loose material and compacted sufficiently to attain
stability (particularly the side slopes), and to sustain the traffic of
any vehicles used to place and compact the lining. Subgrade soils
that swell considerably when wetted can exert sufficient pressure to
damage asphalt linings. Also trapped water, which cannot drain
because of underlying impervious soil layers, can exert sufficient
hydrostatic back pressure to break up large sections of the lining.
When such conditions are likely to occur, it has been recommended
that the faulty material be removed to a depth of at least 0. 3 m (1 ft)
and replaced with selected material. Application of a soil sterilant
is recommended when favorable growth conditions exist.
The chemicals within the limestone sludge should have
no effect on the asphalt, as asphalt is considered stable in the presence
of inorganic chemicals except for high concentrations of sulfuric acid.
The plasticity of asphalt concrete will allow for slight earth movements
or settlements in the subgrade without damaging the liner structure.
C-20
-------
C.3.8 Gunite
"Gunite" is a trade name of the Cement Gun Company
of Allentown, Pennsylvania. Gunite is defined as a mixture of port-
land cement and sand thoroughly mixed dry, passed through a cement
gun and conveyed by air through a flexible tube, hydrated at a nozzle
at the end of the flexible tube, and then deposited where desired by
air pressure. It has been reported (Ref. C-18) that this material has
been successfully used to construct ponds for sewage treatment plants
and for lining canals, flumes, and tanks. "Shotcrete" is similar to
Gunite except that the cement, aggregate, and water are premixed and
then passed through a cement gun. The recommended mix for Gunite
is in the proportions of 1 part of cement to 4-1/2 parts of sand. The
ASTM Types I or II cement are generally used, and the aggregate con-
sists of washed sand. The limits of grading of the fine aggregates as
specified by the Gunite Contractors Association are as follows:
Sieve size Percent passing by weight
9. 52 mm (3/8 in.) 100
No. 4 95-100
No. 8 65-90
No. 16 45-75
No. 30 30-50
No. 50 10-22
No. 100 2-8
Gunite is an extremely dense product that can be easily
applied on 2:1 slopes. It has been recommended that at least a 7.6 cm
(3 in.) Gunite lining with reinforcing of 15.2 cm (6 in.) No. 10 gauge
welded wire mesh be used for sludge disposal ponds.
Gunite provides a good waterproof membrane; however,
experimental testing should be accomplished to obtain actual test data.
C-21
-------
Also, Gunite, like soil cement or concrete, require additives for
protection against attack by the sulfate compounds within the sludge.
C.3.9 Pozzolan Stabilization
The use of fly ash as a pozzolan ingredient mixed with
sand, lime, aggregate, and water to form a cementitious material is
a well established process used to make road bases, airport runway
bases, embankments, and reservoirs. This usage is particularly sig-
nificant when watertightness and crack and sulfate resistance are re-
quired. It has been applied in various mixes by several users, with
the more prevalent mix being Poz-O-Pac, originated and controlled
by the G. and W. H. Carson Company of Philadelphia, Pennsylvania
[now International Utilities Conversion Systems, Inc. (IUCS)]. This
pozzolan stabilized material could be used as a pond base material
superior to and cheaper than asphalt because it would be used at or
near the fly ash supply (i. e. , if the ash is collected and stored so that
it can be used for this purpose).
The Poz-O-Tec process developed by IUCS uses sulfur
sludges that include fly ash (or add fly ash separately) in a process
similar to the Poz-O-Pac process. The new process reportedly
achieves improved engineering properties and can be used without
the addition of aggregate. Similar characteristics may be obtainable
through the use of the Dravo Corporation's Calcilox additive. To
date, the application of these pond linings for sludge disposal has not
been reported; however, the possibility has been considered (e.g. ,
at Commonwealth Edison Company's Will County Station in Joliet,
Illinois).
The potential use of pozzolan stabilized materials as
pond linings will be investigated further in the succeeding portion of
this study.
C-22
-------
C.4 PROCEDURE FOR FABRICATING FLEXIBLE
LINER PANELS AND FIELD INSTALLATION
Flexible sheeting or film is purchased from the sheeting
manufacturer in rolls about 127 - 191 cm (50 - 75 in.) wide by 152 m
(500 ft) long. This sheeting is fabricated into large sections called
panels in the liner manufacturer's factory heat sealing or solvent/
resin bonding together strips of the narrower sheeting. The resul-
tant pond liner panel is normally about 21.3- 24. 4 m (70 - 80 ft) wide
by 106.7 - 137.2 m (350 - 450 ft) long. The panel size depends upon
the size and shape of the pond to be lined, the capabilities of the fac-
tory, and the ability of the field personnel to handle the large sheets
(Refs. C-l through C-3).
The fabricated panels of the flexible liner are accordion
folded in both the longitudinal and transverse directions, packaged for
minimum handling in the field, and boxed at the factory for shipment.
However, the pond lining contractor may elect to fabricate the large
liner panels near the pond site rather than to ship from the factory
area. Factories are located throughout the United States, and the
decision as to factory versus on-site fabrication is essentially a mat-
ter of cost, construction feasibility, and the size and location of the
pond to be lined.
At the pond site, the ground is graded and compacted
to provide a reasonably smooth surface. Compaction of the soil to
90 - 95 percent is advisable to provide a firm base for the pond. The
removal of sharp sticks, stones, and trash reduces the local stresses
on the liner membrane and decreases the chances of developing holes
in the liner. Roots and grasses have a tendency to grow through the
membrane and should be destroyed before lining. The soil should be
sterilized to preclude future growth.
C-23
-------
Several methods of pond liner installation have been
used, but the system that appears to be the easiest to perform is to:
a. Place the accordion folded panel on a flat-bed truck,
a fork lift loader, or other suitable carrier and open
the accordion fold to expose the panel lengthwise by
holding one end of the panel and driving the vehicle
forward. Each panel is positioned adjacent to the
previously opened panel in the pond so that a field
joint can be made.
b. Field seam the liner panels by using a solvent/resin
sealer or taping technique (Figure C-l); other tech-
niques (e.g., field heat sealing, zipper designs, or
sewing in place) are used for specific applications.
The quality control on the factory and field seams is
by visual inspection of the seal which has been pre-
pared based upon accepted company standard oper-
ating procedures.
c. The panel, which is opened lengthwise and bonded to
the previously opened panel, is next opened to its full
width by the construction crew pulling sideways on the
liner.
d. The liners are positioned on the side slopes to fit into
a perimeter trench located approximately 20.3 - 30.4
cm (8 - 12 in.) along the berm surface and still per-
mit bonding to the adjacent panels.
e. Repair of a liner is accomplished by cutting out the
damaged section and bonding in a new piece, or by
installing a patch over a small hole.
C.5 POND DESIGN AND CONSTRUCTION PROCEDURE
In the design and construction of a sludge pond the fol-
lowing general procedures are normally employed:
a. The need for a pond has been established as the result
of new manufacturing or operating processes being
instituted, new or changed laws affecting the accepted
disposal techniques, attempts to reduce costs, or
many other equally urgent reasons.
b. An independent engineering firm or the Company's
in-house engineering office will conduct field surveys
C-24
-------
and experimentation to gather data for detailed
technical and economic analyses to determine the
best location, size, construction materials, special
features, and other requirements for the pond(s).
c. If the project is large and costly, and special financ-
ing is required, arrangements are made through reg-
ular banking circles to obtain the capital for the ini-
tial investment.
d. Detailed construction drawings and plans are made
after all preliminary investigations have been com-
pleted and details agreed upon. Normally, plans
are prepared to solicit bids from the following:
Contractors for dirt movement (e.g. , building
the roads, pond walls, covering the liners with
soil)
Pond lining contractors
Building and fencing contractors
Piping/steam fitting/pumping contractors
Instrumentation and electrical contractors
General contractor for more than one phase
of the work
Construction and start-up schedules are established,
and contracts are negotiated with the winning contractors. Construc-
tion times vary from a few weeks for small ponds like the Pacific Gas
and Electric pond at Barstow, California, 2024 sq m (0. 5 acres), to
about a year for the 1,618,800 sq m (400 acres) at Texasgulf's Moab,
Utah facility.
Construction is undertaken using local labor whenever
possible with the job contractor providing the supervision. This phi-
losophy applies to all the contractors including those who install the
flexible pond linings. There are many local rules, regulations, and
customs that influence how the pond is to be built. The preceding pro-
cedures are general in nature, but they provide an insight into some
of the methods currently being employed.
C-25
-------
C.6 POND SAFETY
Procedures must be made to protect the workers, the
general public, animals, and in some cases, birds, from injuries
associated with the sludge ponds. Some of the standard techniques
that are used and should be evaluated in any sludge pond operation
are summarized below:
a. Fencing - The pond area should be totally enclosed
within a 1. 83 - 2. 44 m (6 - 8 ft) high sturdy fence
(e. g. , chainlink) to prevent intrusion from the gen-
eral public and large animals. In some areas the
fencing must be buried several feet deep in the ground
to retard any intrusion from burrowing animals.
b. Netting - Polypropylene netting material is being used
to prevent birds from landing on oil sump ponds (Ref.
C-19). This netting material is lightweight (5 gm per
1000 sq m) and is currently being fabricated in panels
15. 2 m (50 ft) wide by 60. 96 m (200 ft) long. Guy
wires attached at the berms are stretched across the
ponds, the panels are laid over the wires, and each
panel is laced to its adjoining panel with a Dacron
cord. The polypropylene netting is usable to -45.6°C
(-50°F), but its long-term weatherability is still un-
known because the resin is affected by sunlight. How-
ever, Coastal Engineering Company reports a suc-
cessful 5-year field installation test in New Mexico.
A need for covering sludge ponds has not been shown.
c. Vehicle Travel on Berms - The size of the berms is
a function of the depth and area of the sludge pond and
the local terrain. To protect the employees, who have
a need periodically to drive vehicles along the berm
surface, from accidents during this phase of their
work it is advisable to incorporate a specifically de-
signed road surface into the design of any new large
pond. By incorporating the road into the original de-
sign and engineering, sufficient planning can be given
to the road bed, width of the road, and protective
guard rails.
C-26
-------
d. Security - Companies currently operating large
evaporation or sludge ponds generally have a secur-
ity guard to patrol the area on a periodic basis. This
operation serves not only to discourage intruders,
but acts as an emergency patrol if a person or animal
should get past the protective barriers and should
accidentally fall into the pond.
C-27
-------
REFERENCES
C-l. Personal Communication, W.A. Wheeler and H.C. Ellingston,
Jr. , McKittrick Mud Company, Inc. , Bakersfield, California
(October 1973).
C-2. Personal Communication, C. E. Staff, Staff Industries, Inc.,
Upper Montclair, New Jersey (October 1973).
C-3. Personal Communication, O. E. Hensgen, Waterproofing Sys-
tems, Inc. , Los Angeles, California (September 1973).
C-4. Personal Communication, R. L. Curfman, Texasgulf, Inc. ,
Moab, Utah.
C-5. Chlorinated Polyethylene for Pond Liners, 301-313-72, Dow
Chemical, Midland, Michigan.
C-6. Personal Communication, G. E. Lewis and Pond and Reser-
voir Liners, 821-944-510, Goodyear Tire and Rubber Com-
pany, Akron, Ohio (October 1973).
C-7. Pond, Pit, Reservoir Liners of Hypalon, A70059, DuPont
de Nemours and Company, Los Angeles, California
(October 1973).
C-8. Personal Communication, D. T. Skowlund, B. F. Goodrich
General Products Company, Marietta, Ohio (October 1973).
C-9. Fiber-glass Pit Liner, Anti Pollution Liner, Inc.
(October 1973).
C-10. Personal Communication, R. J. Bennett, Phillips Petroleum
Company, Commercial Development Division, Chemical
Department, Bartlesville, Oklahoma (October 1973).
C-ll. Personal Communication, W. C. Craghill, Stabilization Chem-
icals, Newport Beach, California (October 1973).
C-12. Personal Communication, J. H. Glenn, J.. Harlan Glenn and
Associates, Vitla Park, California (October 1973).
C-28
-------
C-13. Soil-Cement Slope Protection for Earth Dams; Planning
and Design (1971), Soil-Cement Linings for Water Reser-
voirs, Essentials of Soil Cement, PA 0002. 09, and Port-
land Cements, IS004. 04T, Portland Cement Association,
Pacific Southwest Region, Los Angeles, California.
C-14. Bentonite; Its Properties, Mining, Preparation and
Utilization, U. S. Bureau of Mines Technical Paper 609
(1940).
C-15. "Identification and Consideration of Dispersed Soils for
Design and Construction," Paper presented South Region
State Conservation Engineer's Workshop, West Palm Beach,
Florida (February 1972).
C-16. Encyclopedia of Chemical Technology, Vol 3, 2nd Edition,
(1964).
C-17. Asphalt in Hydraulic Structures. MS-12 (March 1965) and
Asphalt Linings for Waste Ponds, IS-136 (August 1966),
The Asphalt Institute, Long Beach, California.
C-18. Personal Communication, J. A. Jedlicka, Pacific Gas and
Electric Company, San Francisco, California.
C-19. Personal Communication, K. Jones, Coastal Engineering
Company, Bakersfield, California (October 1973).
C-29
-------
-------
APPENDIX D
POTENTIAL COMMERICAL UTILIZATION OF
SULFUR DIOXIDE SLUDGES
D. 1. OVERVIEW
As a result of the extensive research that has been
performed to determine the technical properties and characteristics
of the potential commercial products to which sludge may be applied nu-
merous products and applications have been developed. Some of the pro-
ducts and applications would require the consumption of a major portion
of the available sludge'if used nationally on a large scale. However,
these new products would have to compete successfully (both technically
and economically) on the open market with well established manufac-
tured or natural products. Since sludge is a relatively new material
that is not yet available in large quantities throughout the nation, a true
market test has not been made. However, indications are that poten-
tial sludge products will not be competitive enough in the near term to
consume an appreciable portion of the projected supply and that the
principal concern for sludge will be "disposal" and not "utilization."
D-l
-------
This appendix discusses that situation and provides the rationale for
the conclusion just made.
D.2. TECHNICAL STATE OF THE ART
D.2.1 Potential Utilization
Research, development, and investigative activities
have been conducted or sponsored by numerous government and pri-
vate organizations to determine the potential utilization of power plant
desulfurization sludges. Some of the more significant organizations
include: the EPA (Refs. D-l through D-3), the Bureau of Mines
(Ref. D-4), the Federal Highway Administration (Ref. D-5), West
Virginia University's Coal Research Bureau (Refs. D-l, D-2, and
D-6), the TVA (Ref. D-7), The Aerospace Corporation (Ref. D-3),
Combustion Engineering, Inc. (Ref. D-8), International Utilities
Conversion Systems, Inc. (Refs. D-9, D-10, D-ll, andD-12), the
National Ash Association, the Dravo Corporation (Ref. D-13), and
the Chicago Fly Ash Company. These efforts have identified desul-
furization sludge as a unique raw material that has some potential
use in the manufacture of products now using fly ash as an additive,
or in new products or applications.
An inspection of the products listed for which fly ash
is used as an additive, and the applicability of sludges to these products,
provides an insight into the great difficulty attached to the possible
utilization of the throwaway sludge. For example, an annual survey
conducted by the Edison Electric Institute (EEI) (Ref. D-14) presents
a breakdown (Table D-l) of ash collection and utilization in the United
States for 1972. Three significant factors regarding sludge have been
derived from this table and previous EEI surveys (Ref. D-3), namely:
the low percentage of available fly ash that is actually used; some
technical capability, but an economic inability to apply sludge in most
uses of fly ash; and the economic inability to apply sludge in the major
uses of bottom ash and boiler slag.
D-2
-------
Table D-l. ASH COLLECTION AND UTILIZATION YEAR 1972
AS REPORTED IN REFERENCE D-14
(tons)
Ash utilization
1.
2.
3.
4.
Ash sold or used internally (This
includes ash sold by a utility or its
sales agent and/or ash used by a
utility)
a. Mixed with raw material before
forming cement clinker
b. Mixed with cement clinker or
mixed with cement (pozzolan
cement)
c. Partial replacement of cement
in:
Concrete products (blocks,
bricks, pipe, etc.)
Concrete
Dams and/or other mass concrete
d. Lightweight aggregate
e. Fill material for roads, con-
struction sites, land reclamation,
etc.
f. Stabilizer for road bases, parking
areas, etc.
g. Filler in asphalt mix
h. Miscellaneous
Total Item No. 1
Ash removed from plant sites at no
cost to utility, but not covered in
categories listed under Item No. 1
Total ash utilized (Item Nos . 1 and 2)
Total ash produced
Fly ash
116, 178
72,201
143, 112
301.689
67,880
133,901
584,860
153,629
139.937
426,737
2,140, 124
1,495, 156
3,635.280
31,808,065
Bottom ash
30,248
_
22. 678
-
-
23,521
750,660
24, 648
14, 634
921, 193
1,787,582
814,336
2,601,918
10,672,860
Boiler slag
(if separated
from
bottom ash)
110,000
_
.
-
.
-
477,293
4,683
43.431
701,663
1.337,070
1,235
1,338.305
3,781,660
D-3
-------
Table D-l shows that 7 percent of all fly ash produced
was utilized in the products noted, and that another 4.8 percent was
removed from plant sites at no cost to the utility (some was used and
the remainder was probably stored). In addition, there is the utiliza-
tion of bottom ash and boiler slag, principally as a constructional fill
material with which the sludges cannot compete economically because
the bottom ash and slag are used as aggregate without appreciable
processing. When all these applications for power plant ash are con-
sidered, the maximum utilization of the total produced is about 16 per-
cent. Of these applications, the "stabilizer for road bases, park-
ing areas, etc." category is the only current use in which the sludge
should be able to compete technically and economically on a national
basis in the ash market. As an artificial aggregate, it can also enter
some local markets depending on the supply of natural aggregate.
However, the current ash-usage categories of road bases and aggre-
gate account for a usage of less than 1 percent of the total ash produced.
Also, it has been shown (Ref. D-3) that for a given power plant, an
alkali scrubber system will produce up to three times as much sludge as
the amount of ash produced without scrubbing. Therefore, with the
by-product production increased as much as three times at a given plant
and the potential utilization in the near term being inconsequential on
a national basis, the disposal of the by-product appears to be the
principal method for handling these materials.
D.2.2 Material Properties
A theoretical chemical analysis of the sludge reveals the
wide range of values attached to the chemical constituents depending
on the sulfur and ash content of the coal burned. Physical phases vary
widely in the same manner. Table D-2 shows the values for 10 and
20 percent ash content coal and for a sulfur content of 1 and 4 percent in
D-4
-------
Table D-2. LIMESTONE SLUDGE -- THEORETICAL VARIATIONS
IN CHEMICAL AND PHASE COMPOSITION WITH
VARIATIONS IN SULFUR AND ASH CONTENT OF COAL
BURNED AS REPORTED IN REFERENCE D-3
The following conditions were used in this theoretical analysis: the sulfur collection
system was assumed to be 95 percent efficient, limestone was added at 11 0 percent
stoichiometric and was assumed to be 100 percent CaCO,, and the only ash collection
device was a wet scrubber.
Composition
Si°2
A12°3
Fe2°3
£ Ti02
1 CaO
B MgO
u so2, so3
Other
LOIa
Relative
Quantity
t, B Gypsum"
'I? rt Free Lime
* 0. Fly Ash
Typical
fly ash
(unmodified)
10 percent ash in coal
20 percent ash in coal
Sulfur content of coal
1 percent
4 percent
1 percent
4 percent
Weight percent
45
23
19
1
2
1
0.7
2.3
6
1.00
0
2.0
97.3
30.6
15.7
12.9
0.7
14.4
0.7
17.5
1.6
4. 1
1.47
28.3
2.8
66.3
16.2
8.3
6.8
0.4
28.5
0.4
36.2
0.8
2.2
2.77
60.1
4.5
35.1
36.8
18.8
15.5
0.8
9.5
0.8
10.8
1.9
4.9
1.22
17.5
2.3
79.5
23.9
12.2
10.1
0.5
21.5
0.5
26.9
1.2
3.2
1.88
43.5
3.7
51.6
Loss on ignition.
Values given for gypsum include both sulfates and sulfites, but exclude combined
water.
D-5
-------
each case. The variations in properties are large, and the differences
are considerable when compared to fly ash. The principal problems
that face the utilization of the sludge are, therefore, centered in
several areas:
a. The sludge quality is affected appreciably by the
sulfur content of the coal burned and by the efficiency
of the combustion and scrubbing process.
b. The sludge contains sulfur that creates additional
problems of sulfur gas collection for manufacturing
processes requiring high temperatures.
c. The pozzolanic (concreting) properties of the sludge
are weak when compared to those of fly ash.
d. The volume of sludge produced will be much greater
than that of the ash produced without the scrubbing
process.
/
On the positive side, as appropriate, the sludge contains:
some pozzolanic properties, nominal amounts of unreacted lime, and
appreciable amounts of gypsum.
The sludge qualities shown in Table D-2 consider the
collection of fly ash in the scrubber. At power plants where efficient
fly ash collection systems exist, the fly ash will be collected upstream
of the scrubber, and very little fly ash will exist in the sludge. There-
fore, for essentially all developments for sludge usage (other than
gypsum production and processing for one claimed landfill method)
fly ash will have to be added to provide the pozzolanic properties
necessary for structural qualities.
D.2.3 Potential Product Applications
Technical developments for the potential usage of the
sludge have been made for the most part by: the Coal Research Bureau
at the University of West Virginia under the sponsorship of the EPA;
The G. and W. H. Corson Company (now International Utilities Con-
version Systems, Inc.), Philadelphia, Pennsylvania; Combustion
Engineering, Inc., Windsor, Connecticut; and Michigan Technological
D-6
-------
University, Houghton, Michigan. Uses being studied or considered
include those for which fly ash is being used or could be used, plus
new developments. Table D-3 summarizes those considerations and
includes uses that may be possible regardless of how slight their
potential is.
Table D-3. POTENTIAL PRODUCT APPLICATIONS
Uses same as or similar to
those for fly ash
Potential new uses
Concrete admixture (struc-
ture and products)
Manufacture of portland
cement
Fired brick
Filler in bituminous concrete
Road base course, parking
lots, etc.
Structural fill
Soil amendment
Mine void fill
Neutralization of acid mine
drainage
Autoclaved products -
gas concrete, bricks,
mineral aggregate
Hot press sintering -
pipes, metal coatings
Gypsum products -
wallboard, plaster
Mineral recovery
Sulfur or sulfuric
acid production
Artificial aggregate
D-7
-------
D.2.4 Use Inhibitions
The difficulty associated with the small usage of fly
ash in the United States and the weak projections for the potential use
of sludge products are best seen by examining the inhibitions to the
use of fly ash and by comparing fly ash properties with those of
sludge. It has been determined that the major inhibitions to the use
of fly ash, which generally apply to the inhibitions to the use of
sludge, are:
a. Highly variable chemical and physical properties
b. Lack of control or availability of usable supply when
needed
c. Necessity for appreciable capital expenditures to
classify, handle, store, or process materials
d. High transportation costs
e. Inability to compete economically with other materials
Thus it has been shown (Ref. D-3) that although there
are many uses for the fly ash considering already developed techno-
logies, and that these potential products are in many ways equal to
or superior to existing materials, its actual utilization is particularly
limited. The situation is worse for sludge as an additive in the pro-
duction of commercial products as described in the following
discussion.
When the potential technical uses of the sludge are
related to the basic properties and qualities mentioned in Paragraphs
D.2.2 and D.2.3, various factors are applicable to the potential uti-
lization of large tonnages of sludge on a national basis. These factors
identify reasons where: (a) the sludge product is expected to be tech-
nically or economically inferior to a fly ash product (which is already
in a weak marketing position as shown in Table D-l, (b) its production
or use may create a pollution problem, or (c) it may be technically
D-8
-------
sound, but not economically competitive on a wide scale. These
factors are:
a. The sludge is produced in a wet state and will have to
be dewatered or dried for many uses to prevent agglom-
eration due to the interaction of the pozzolan with self-
contained lime in the presence of water. Agglomera-
tion can require a grinding operation depending on the
fineness required for structured concrete qualities.
b. Its pozzolanic properties for concrete product applica-
tions are reduced because the sum of the SiO2, ^203,
and Fe2O3 content and consequently, the glassy phase
is reduced (see Table D-2).
c. Sludge properties can be highly variable (see Table
D-2); therefore, blending may be required for many
applications.
d. The use of sludge in the manufacture of sintered pro-
ducts has three distinct disadvantages:
' Sulfur is released and would have to be collected.
Decomposition of sulfates (or sulfites) takes place
at temperatures below sintering and results in the
physical destruction of the "green formed" product.
The fusion temperature is such that a short range
exists between sintering and melting, thereby re-
quiring a sophisticated temperature control system
for the sintering process.
e. The soluble salt content of the sludge presents a pro-
blem of leaching heavy metals to ground waters for
certain applications (e.g., soil amendment and acid
mine drainage neutralization).
f. There is the problem of nondeveloped or high-cost
technology for mineral recovery to obtain aluminum
(Ref D-l), iron, titanium, silicon, and lime.
g. Severe competition from a saturated current market
for products such as gypsum^, mineral wool (Ref. D-3)
sulfur, and sulfuric acid (Refs. D-3 and D-8).
Gypsum is the only sludge product sold overseas; it is marketed in
Japan where the material is competitive (Refs. D-4 and D-15). In
Reference 4, it is projected that in Japan in the mid-1970s, the
sludge-gypsum supply will exceed demand.
D-9
-------
h. High capital investments are required to produce
autoclaved products.
In consideration of the factors noted, it should be recog-
nized that of all the potential large-scale uses for the sludge, the most
promising are: (a) road base materials (Refs. D-5, D-6, D-10, and
D-12). and artificial aggregate (Ref D-9) and (b) landfill or land re-
clamation when appropriately conditioned to prevent leaching (Refs.
D-8, D-9, D-ll, and D-13). The former are considered commerical
utilizations of the sludge while the latter is generally considered a
disposal process. As a road building material, the sludge has a po-
tential for large tonnage utilization; however, it must compete with
existing materials such as crushed rock and bituminous concrete
(Ref. D-3). Although the sludge-produced road base materials are
believed to be superior in regards to strength, stability, water-tight-
ness, and crack resistance when compared to competing products,
a comparatively thin layer of crushed rock in particular is accepted
by most specifications and agencies and is generally used because it
is cheaper. Only in local areas where crushed rock is unavailable or
not allowed would sludge-produced materials be considered. Artifi-
cial aggregate could also consume large masses of sludge, but its
demand is only local where natural aggregate is not available. In
the near term, this is not expected to be a widespread condition.
D.3 POTENTIAL UTILIZATION CONCLUSIONS
Because the sludge is not expected to find large-scale
commercial outlets in the near term, it is concluded that its potential
utilization as an ingredient in a commercial product is low and that
the major consideration for its disposition must be disposal. The
principal applications then would be: landfill, artificial aggregate to
be used in a landfill and possibly to be reclaimed later, and possibly
for both the filling of mine voids and the neutralization of acid mine
D-10
-------
drainage. All of these applications will require the appropriate
determination of environmental impact on the earth and water supplies,
and the appropriate treatment or conditioning necessary for the en-
vironmentally sound disposal of the material.
D-ll
-------
REFERENCES
D- 1. Technical and Economic Evaluation of Dewatering,
Production of Structural Materials, and Recovery of Alumina
from the Limestone Modified Fly Ash Produced by a Lime-
stone Wet-Scrubbing Process, Final Progress Report,
Contract EHS D-7-11, Environmental Protection Agency
(Not Released).
D-2. L. Z. Condry, R. B. Muter, and W. F. Lawrence, "Potential
Utilization of Solid Waste from Lime /Lime stone Wet Scrubbing
of Flue Gases, " Coal Research Bureau, West Virginia
University, Proceedings of Second International Lime/Lime-
stone Wet Scrubbing Symposium, Volume I, Environmental
Protection Agency (June 1972).
D-3. Final Report Technical and Economic Factors Associated
With Fly Ash Utilization. EPA No. APTD 1068, The Aerospace
Corporation, El Segundo, Calif. , Prepared for Control
Systems Division, Office of Air Programs, Environmental
Protection Agency (26 July 1971). (EPA Contract
68-02-1010 (Aerospace Report No. TOR-0059(6781)-1.
D-4. J. P. Capp and J. D. Spender, Fly Ash Utilization, A
Summary of Applications and Technology, Information Circular
8483, Bureau of Mines, U.S. Department of the Interior
(1970).
D-5. R. H. Brink, "Use of Waste Sulfate on Transpo '72 Parking
Lot, " Paper presented Third International Ash Utilization
Symposium, Pittsburgh, Pennsylvania (13-14 March 1973).
D-6. J. F. Slonaker and J. W. Leonard, "Review of Current
Research on Coal Ash in the United States, " Paper presented
Third International Ash Utilization Symposium, Pittsburgh,
Pennsylvania (13-14 March 1973).
D-7. A. V. Slack and J. M. Potts, "Disposal and Uses of By-
Products from Flue Gas Desulfurization Processes - Introduc-
tion and Overview, " Paper presented Environmental Protec-
tion Agency Flue Gas Desulfurization Symposium, New Orleans,
Louisiana (14-17 May 1973).
D-12
-------
D-8. W. C. Taylor, "Experience in the Disposal and Utilization
of Sludge from Lime /Lime stone Scrubbing Processes,"
Paper presented Environmental Protection Agency Flue Gas
Desulfurization Symposium, New Orleans,' Louisiana (14-17
May 1973).
D-9. J. L. Minnick, "Fixation and Disposal of Flue Gas Waste
Products: Technical and Economic Assessment," Paper
presented Environmental Protection Agency Flue Gas
De sulfur ization Symposium, New Orleans, Louisiana (14-17
May 1973).
D-10. J. L. Minnick, "Multiple By-Product Utilization, " Paper
presented Third International Ash Utilization Symposium,
Pittsburgh, Pennsylvania (13-14 March 1973).
D-ll. "Putting Industrial Sludges in Place," Environmental Science
and Technology, b (10) (October 1972).
D-12. J. L. Minnick, "Structural Compositions Prepared from
Inorganic Waste Products, " Paper presented Annual Meeting
of the American Association of State Highway Officials,
Miami Beach, Florida (5-10 December 1971).
D-13. J. G. Selmeczi, and G. R. Knight, "Properties of Power
Plant Waste Sludges," Paper presented Third International
Ash Utilization Symposium, Pittsburgh, Pennsylvania
(13-14 March 1973).
D-14. Ash at Work, National Ash Association, Volume V, Number
3 (1973).
D-15. J. Ando, "Status of Japanese Flue Gas Desulfurization
Technology and Utilizing and Disposing of Sulfur Products
from Flue Gas Desulfurization Processes in Japan, " Paper
presented Environmental Protection Agency Flue Gas
Desulfurization Symposium, New Orleans, Louisiana (14-17
May 1973).
D-13
-------
-------
APPENDIX E
COMMENTS ON SELECTED POWER PLANT
SLUDGE DISPOSAL PROGRAMS
This Appendix contains comments on four different
approaches to sludge disposal, each being investigated by one of four
different power companies. Progress is being made by each of these;
however, none has reached the point of steady-state operation and it
is expected that all of these programs will undergo change either with-
in themselves or in succeeding applications as the technology improves.
These approaches and others will be investigated during the remainder
of this program to form as complete a survey of all industrial progress
as is possible.
E. 1 COMMONWEALTH EDISON, WILL COUNTY
STATION, JOLIET, ILLINOIS
The sludge at this station is produced by a full-scale
scrubber on a 175 MW boiler. The disposal problem is compounded
by the unavailability of sufficient acreage to contain the sludge, the
immediate proximity to the Illinois River, and a high water table.
Since Commonwealth Edison operates in high-density population areas,
considerations given to disposal techniques at the Will County Station
E-l
-------
can be reasonably extended throughout the company's power system.
In this regard, the company has addressed sludge disposal with con-
sideration given to the following priorities: (a) Economic Land Use -
pit disposal or landfill areas within short haul distance of power plants
are not considered for thixotropic sludge because they may not allow
subsequent economic development of the land after filling, (b) Environ-
mentally Safe - the sludge must not contaminate by leaching to ground
water or nearby water courses, (c) Disposal Costs - the disposal
technique must minimize transportation and eliminate excessive han-
dling, thereby reducing disposal costs. Commonwealth Edison has
decided, therefore, that the sludge must be conditioned so that it will
not leach to the ground water and that it must serve adequately as a
landfill material because the final disposal is planned on land that is
not owned by the power company.
Commonwealth Edison has consulted with several com-
mercial sludge processors, but because of the economics involved they
are attempting to develop their own fixation process with the aid of the
Chicago Fly Ash Company who, in turn, has employed the Civil Engi-
neering Department of the University of Illinois for assistance. Their
plans are to extract thickener underflow to which lime and fly ash and
one wet additive will be intermixed with the sludge in a pug mill and
loaded in a dump truck. The truck will transport these ingredients to
one of two 10-ft-deep clay basins that total about 7 acres. An arbi-
trary lining thickness of 1 foot was chosen for these basins. The clay
has a permeability coefficient of about 10" cm/sec whereas the cured
material is expected to have a coefficient in the range of 10 to
_o
10" cm/sec. The material cures for approximately 1 month and is
inspected by local authorities to obtain permission for each site dis-
posal. It will be dredged from this basin and hauled to a nearby land
fill area while the second basin is being filled.
E-2
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The present additives are reported to be approximately
10 percent lime and 20 percent fly ash on a dry basis. A development
program is planned to reduce costs by increasing fly ash and reducing
lime contents. Their present philosophy is an acknowledged over-kill
to avoid possible variability in sludge chemistry. Subsequently they
hope to optimize for steady-state operation, but they realize they must
plan for scrubber downtime such that boiler operation is unaffected.
Tests are still being conducted to improve the final product by the
elimination of cracks during curing and to verify impermeability in
the field. They have not yet determined whether their leachate con-
tains trace heavy metals. They have determined that with enough lime,
a concrete-like product with 3000 psi strength can be obtained. For
landfill disposal purposes, a product with a strength far less than this
is desired because of the subsequent need to dredge it from the cure
pond.
In the present operation, sludge is being dredged from
an interim pond, loaded in a Redi-mix truck to which the fixation ingre-
dients are added. The truck mixes these materials enroute to one of
the cure ponds where the materials are unloaded. The cost has varied
between $5. 25 to $10. 00 per ton of sludge (50 percent solids); the higher
value results from specific case operations that include machinery
breakdown and repair. These costs are only operating and maintenance
costs and do not include pond costs or $600,000 of capitalization.
Unofficial estimates for disposal including all costs after optimiza-
tion for steady-state operation are placed at $5. 00 per ton. Besides
the inclusion of a pug mill and the replacement of the Redi-mix truck
with a dump truck, it is believed that a vacuum filter must be installed
between the clarifier and pug mill to reduce the water content of the
waste. Their present estimate for flue gas scrubbing at Will County
has been placed at $100/kW capacity.
E-3
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Commonwealth Edison does not know whether their
sludge may pose an environmental hazard. Liquors are saturated in
sulfate, and present chloride content has been measured at 800 ppm.
At this concentration, evidence of corrosion-assisted erosion is ap-
parent. The recirculation system has been installed or replaced with
rubber lined piping and pumps, and no further problems have been
experienced.
Commonwealth Edison is under way in a disposal de-
velopment program designed to satisfy their particular disposal re-
quirements. All data collected represent present status and are not
firm. It is expected that firm values regarding the technical quality
of the fixed materials and attendant costs will not be adequately de-
termined for at least another year.
E. 2 NORTHERN STATES POWER COMPANY,
SHERBOURNE COUNTY STATION,
MINNEAPOLIS, MINNESOTA
This new station will have a total capacity of 1360 MW
and will be on-line in 1975/76. The plant will use western coal having
a sulfur content of 0. 8 percent and will guarantee a 50 percent sulfur
removal using a limestone scrubber. The sludge will be sluiced to
clay-lined ponds (with 18-in. -thick linings) and excess water will be
returned to the scrubber system. An initial (10-year) pond will be
approximately 65 acres with 40 ft dikes. A second basin will be added
later bringing the total capacity to 160 acres for an expected 35- to
40-year plant life. This site is located on bluffs above the Mississippi
River at an elevation of 965 ft; the normal river water elevation is
920 ft. Pond costs are in excess of $30, 000 per acre.
The scrubbing system will use two stages, a variable
throat venturi and a marble bed scrubber. Fly ash will be collected
simultaneously with the sulfur sludge. The Sherbourne County permit
E-4
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requires 50 percent sulfur removal and 99 percent particulate removal.
The venturi removes 55 percent of the total 70 percent sulfur removed
and 90 percent of the particulates. The second scrubbing stage is
required for particulate removal. It was speculated that newer
plants would use precipitators for fly ash removal predominantly
because it would increase operating flexibility, reduce erosion, pro-
vide for the sale of dry ash, and allow single-stage scrubbing.
The Sherbourne County Station scrubbing unit design was
based on experiments presently being conducted at the Black Dog Sta-
tion on a pilot scrubber. The coal ash contains 17 percent CaO, and it
was found that only a 20 percent stoichiometric addition of limestone
produces satisfactory scrubbing efficiencies. The use of fly ash as a
sorbent predicated the collection of particulates in the scrubbing unit.
The company's Black Dog Power Station operation is a research effort
for determining scrubber parameters; however, this research philos-
ophy was not extended to considerations regarding waste disposal.
Trace metal analyses on sludge and fly ash were not
known. The possibility exists that the Sherbourne County Station dis-
posal pond will undergo environmental monitoring by the analysis of
leachate from wells placed around the pond.
E.3 LOUISVILLE GAS AND ELECTRIC COMPANY,
PADDY'S RUN STATION,
LOUISVILLE, KENTUCKY
This full-size scrubber is operating on a 70 MW 25-year-
old boiler that has an 18 percent operating efficiency factor and runs
approximately 40 percent of the time. The deep mine southern Kentucky
coal used at this station has a sulfur content of approximately 3-1/2 per-
cent and an ash content of 15 percent. The scrubber operates on a fully
closed-loop cycle and attains an 85 percent sulfur removal efficiency.
The disposal process includes extracting underflow from the thickener,
E-5
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vacuum filtering the underflow to approximately 55 percent solids, and
trucking it 1 mile to a state borrow pit. No environmental control is
applied. Disposal costs are not well defined; however, it is believed
that the hauling cost is approximately $0. 50/ton at this particular
site. The company uses its own 12-ton capacity dump trucks.
Disposal of this material is not considered representa-
tive of company policy. Louisville Gas and Electric Company has com-
mitted itself to $165M over 10 years for scrubbing equipment. Dis-
posal plans are now considering chemical fixation and possible use of
fixed wastes in land salvage of strip mined areas or as a support
material for recovery of the 30 to 60 percent of the coal remaining in
deep mines. No estimation of disposal costs has been made, but it is
assumed that $70/kW capacity is a representative figure for scrubbing;
however, this does not include disposal (disposal is a coal cost and is
directly transferred to customers).
The Paddy's Run Station is unique in that it uses a waste
carbide sludge (calcium hydroxide) as the sorbent. The system oper-
ates in a transient between pH 5 and 11 by the reaction of bisulfite with
the calcium hydroxide. The resulting sludge is about 95 percent sulfite;
oxidation of the liquors is retarded such that the sulfate in the liquors
is about 400 ppm.
All sludge is collected independently of fly ash. Pre-
cipitators now exist on all stacks and are planned for all future plants.
A primary consideration for upstream fly ash removal is the control
of erosion and the elimination of boiler downtime during periods of
scrubber maintenance. Their evaluation shows that savings by boiler
downtime avoidance more than offsets the precipitator costs. Alter-
native disposal schemes consider collection of thickener underflow at
20 to 30 percent solids to which dry collected fly ash might increase
solids content to 50 to 60 percent, or to pass the underflow through a
filter to get 50 percent solids to which fly ash might be added.
E-6
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Louisville Gas and Electric Company has a well run,
full-scale scrubber demonstrating the capability of this technique for
SO? control. Although plans for environmentally sound disposal
techniques were discussed, no implementation of such plans was
observed.
E.4 DUQUESNE LIGHT COMPANY, PHILLIPS
STATION, PITTSBURGH, PENNSYLVANIA
This is an operational scrubber system. The sludge
disposal system consists of removing the underflow from the clarifier,
treating it with Calcilox (a Dravo material), and allowing it to set
for 30 days in one of three curing basins. A disposal development
program will be conducted at this station. The cured sludge will be
removed from the curing basin and hauled about 1 mile to the disposal
demonstration site. This site includes one unlined pond and two ponds
lined with Hypalon. Each pond will have underdrainage and overdrainage
piping to collect water for testing. No definitive costing data are avail-
able; however, Duquesne notes that their present fly ash disposal sys-
tem consists of dredging fly ash from a lagoon and hauling it about
1 mile to a landfill site, compacting it, and seeding it. The fly ash
contains approximately 18 - 20 percent water and costs between $2. 50
and $3. 00/ton for disposal. They equate this to approximately $0.40/
ton of coal burned. By comparison, they equate the cost of sludge dis-
posalon a dry basis to approximately S3. 00/ton of coal. Those
values include capital cost and, in the case of the sludge, the material
will be eventually covered with top soil and seeded. Also, they are
not to be considered firm rates. Other cost estimates are given in
Section 7.2.
This plant uses eastern coal containing 20 percent ash
and 2 percent sulfur. The scrubber sulfur collection efficiency is
approximately 90 percent. In the combustion process 80 percent of
the ash produced is fly ash and the remainder is bottom ash. A
E-7
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primary consideration in their design for sludge disposal is land reuse
possibly as a consequence of strong state regulations with regard to
waste disposal. In addition, the sludge must not contaminate the en-
vironment. Both the Federal EPA and State Agencies have stated their
satisfaction with the leachate from their fixed sludge. Duquesne Light
Company is conducting one of the more comprehensive research and
development programs with respect to disposal technology but, as with
other companies, their efforts are constrained by their own equipment
and restricted to their unique condition.
E-8
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APPENDIX F
TOXIC EFFECTS OF TRACE ELEMENTS
F. 1 INTRODUCTION
The determination of heavy element toxicity is dependent
upon observed physiological effects resulting from either carefully con-
trolled experiments or from an environmental catastrophe of epidemic
proportions. Clinical experiments rarely if ever precede the observed
consequence of illness and death that often results from acute exposure
to specific element intoxication. Moreover, health hazards from clini-
cal testing preclude these experiments so that the relationship between
exposure and the effects on humans is most often evaluated from
the effect on animals. Thus, the resulting threshold or exposure
limits for humans are not always established with the certainty that
may be desired. The role of trace elements in man's biological pro-
cesses is only now beginning to be understood: many elements toxic
to man in relatively high concentrations are essential to his health in
trace quantities.
Nine elements found in nature in trace quantities (chro-
mium, cobalt, copper, iodine, iron, manganese, molybdenum, sele-
nium, and zinc) are essential to man's life or health. They are
F-l
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probably important catalysts for differing biological functions. In
addition, vanadium, nickel, fluorine, and arsenic are suspected of
having useful biological functions. Other elements, which are now
considered inert, are found in human tissue and may perform useful
roles in the body, but the study of their biological activity has not been
undertaken. Cadmium, mercury, and lead have no known biological
function and can act synergistically with other substances to increase
toxicity. Once in the human system, their toxic effects are cumulative
and are harmful to the degree that the dosages and resultant concentra-
tions approach a lethal threshold. Even those trace elements having
proven biological functions, when ingested at high concentrations, can
produce disease either by their accumulative effect or by inhibition of
natural functions.
From the two known accumulative diseases, hepatolen-
ticular degeneration from copper and idiopathic hemochromatosis from
iron, accumulative diseases are suspected for other essential cations--
chromium, manganese, cobalt, and possibly zinc and vanadium. The
medical profession has long recognized that all essential trace ele-
ments are toxic in excess. If it were not for homeostatic mechanisms
that reject excesses and conserve deficiencies, man would have to
regulate his intake voluntarily. For elements such as cadmium, lead,
and mercury to which man has experienced only recent exposure, it
is unlikely that adequate homeostatic mechanisms have developed. In
these cases trace elements are absorbed, accumulated, and eventually
lead to the development of disease. Cadmium represents one of the
more serious toxic elements because it not only causes kidney and
liver dysfunction, but also interferes with the natural function of zinc
leading to arterial hypertension and toxemia of pregnancy.
In making an assessment of the toxicity created by
stack-gas scrubber sludge, a literature search was conducted to de-
termine the toxic limits of the trace elements present in fossil fuels
F-2
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and limestone. The following discussions provide a short review for
some of these elements.
F.2 LITERATURE SURVEY
F.2. 1 Beryllium
Beryllium and its compounds (Ref. F-l) are capable of
including acute or chronic pathologic changes in a number of human
tissues. Fulminating and fatal cases of pneumonitis, with pulmonary
edema, have developed after exposure to massive concentrations of
beryllium compounds. Lesions of the skin and mucous membrane of
the eyes and respiratory tract have been evoked by soluble beryllium
salts, but these pathologic processes are not serious even in acute
cases.
Chronic beryllium disease including berylliosis and
pulmonary granulomatosis have occurred among individuals with known
industrial exposure to beryllium and also among those with no known
accountable beryllium exposure. In the latter cases there exist un-
certainties as to whether the degree of exposure has been grossly under-
estimated and whether there exist individual susceptibilities to the
disease. As a consequence of these uncertainties, standards have been
set for beryllium that are among the most stringent of any recognized
toxic material. The in-plant concentration of beryllium is limited to
2 ng/m as an average daily concentration with a maximum concentra-
tion limit of 25 fig/m for any short-time exposure. An average
monthly concentration in a plant's neighborhood is limited to 0.01 jig/m
with a maximum discharge of 10 g/day not to be exceeded on any day
for each beryllium facility. The relationship has never been established
between exposure and acute or chronic beryllium disease.
Since the discovery of the disease in the early 1940's and
the establishment of standards in 1948, beryllium ore refineries and
processing plants have taken the necessary precautions that have nearly
F-3
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eliminated the occurrence of beryllium diseases in industrial situations.
Air sample data collected during the time between the recognition of
the disease and the implementation of safety measures in plants pro-
cessing beryllium and its alloys have indicated that the air quality
standards had been exceeded manyfold, continuously and probably for
several years, without apparently producing the chronic disease. The
uncertainties, concerning the quantitative relationships between the
severity and duration of the exposure and the occurrence of the chronic
disease, raise questions as to the need for limits as low as those pro-
mulgated. The paucity of evidence on which to establish alternative
limits has rendered these standards not as precise criteria for human
safety, but rather as guides to acceptable industrial and technological
practice in the matter of hygiene.
The hazard of severe toxicity from beryllium is experi-
enced exclusively through the inhalation of fumes and vapors of beryl-
lium and its compounds. The primary sources of these materials in
the atmosphere are beryllium processing plants and electric power
generating plants. Since the imposition of standards, neighborhood
exposure levels have been well under 0.01 |o.g/m . Although insuffi-
cient data exist, urban atmospheres typically contain far less than
0.001 fa.g/m of beryllium, and its source has been credited to ultrafine
particulates, presumably fly ash originating from the combustion of
coal.
F. 2. 2 Cadmium
Cadmium (Ref. F-2) has no known function in the human
body and is accumulated in the kidneys and liver causing dysfunction in
both organs at high body concentrations. Its toxicity is further aggra-
vated by a long biological half-life, possibly as long as 1 year. Cad-
mium can enter the human body from natural sources by both inhalation
and ingestion. Brief inhalations of high concentrations of cadmium
compounds can give rise to severe, often fatal, pulmonary edema.
Exposure for longer periods at lower concentrations of cadmium
F-4
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compounds can give rise to chronic pulmonary disorders characterized
as emphysematous changes.
Serious illness and death have occurred by acute poison-
ing from ingesting foods containing cadmium. Long-term exposure to
cadmium from ingestion will develop renal tubular dysfunction, princi-
pally proteinuria, glucosuria and amino-aciduria, and changes in the
metabolism of calcium and phosphorus. In addition, osteomalacia,
hypertension, anemia, liver dysfunction, and testicular changes have
been noted from long-term exposure to cadmium.
The absorption of cadmium has been determined to be
about 5 percent from ingested and as much as 25 percent from inhaled
cadmium. The kidneys and liver concentrates cadmium and will con-
stitute one-half of the body burden of a normal adult. Whereas a
normal adult may accumulate a total body burden of about 30 mg from
exposure to natural levels, an accumulation of 60 mg within the kidney
alone would be required to initiate renal dysfunction. However, an
increase in cadmium accumulation by a factor of ten differentiates
"normal" adult levels from the level necessary to give rise to kidney
disorders in a 50-year life span. (A decrease in cadmium levels
accumulated within the body has been observed in individuals 50-60
years of age. )
Humans are exposed to cadmium through food, water,
and air: ingestion is the most important route of accumulation typically
constitutuing 90 percent (2. 5 (ig) of the daily contribution to the body
burden. In uncontaminated areas, most foodstuff will contain less than
0.05 ppm of cadmium and the daily intake probably will be about 50 (j.g.
Liver and kidney from animals, shellfish, and certain contaminated
grains are primary sources of cadmium at concentrations greater than
0.05 ppm. In water the normal concentration of cadmium is less than
1 ppb and becomes significant relative to total body burden only when
the concentration in drinking water exceeds 10 ppb.
F-5
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The normal concentration of cadmium in urban air is
about 0. 05 g/m and will not contribute significantly to the daily intake.
However, since a considerably larger percentage of inhaled cadmium
compared with ingested cadmium will be expected to be absorbed, an
increase in air concentration to 0. 5 g/m would contribute equally to
body burden from ingested sources.
F. 2. 3 Mercury
Mercury (Ref. F-3) enters the human body by both in-
gestion and inhalation in both inorganic and organic forms. Only about
2 percent of ingested inorganic mercury is absorbed by the body where-
as alkylmercurial absorption has been estimated at more than 90 per-
cent. After exposure to mercury vapor, mercury accumulates in the
brain in quantities far in excess of that which would result from an
equivalent amount of ingested mercury. Metallic mercury and inor-
ganic mercury compounds attack the liver and kidney preferentially,
but in ordinary exposure they are excreted before serious injury is
incurred. Organic mercury compounds are more dangerous because
they preferentially attack the central nervous system, primarily the
motor and sensory system. In cases of acute alkylmercurial intoxi-
cation these symptoms are not reversible, indicating that permanent
brain damage has occurred. In cases of chronic intoxication by alkyl-
mercurial compounds, the symptoms are similar to those for acute
alkylmercurial intoxication and because of the relatively long half-life
(70 days), continued exposure could lead to progressive and sometimes
complete loss of muscular control and finally death. While elemental
or inorganic mercury poses no real threat to man or the environment
directly, the ability of any form of mercury entering the aquatic en-
vironment to be converted to methylmercury subjects all forms of
mercury to a common biological threat.
F-6
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There is still some uncertainty as to the level of
mercury concentrations that are required for lethal doses to man.
For elemental or inorganic mercury, lethal doses are likely to be en-
countered only in acute or seriously chronic exposure from industrial,
mining, and refining operations. However, methylmercury intoxica-
tion can occur by the consumption of fish and shellfish and other heavily
contaminated foods. An average daily intake of methylmercury from
all sources for persons on a varied diet has been estimated at 0. 02 mg/
day, whereas an intake of 0. 3 mg/day has been estimated as a maxi-
mum chronic dose required before primary symptoms of mercury in-
toxication are apparent. At 0. 5 mg/day intake, overt symptoms occur.
An intake of 0. 3 mg/day represents consumption of 2 Ib of food a day
contaminated with 0. 5 ppm methylmercury. Thus a daily mercury
intake 15 to 25 times that normally experienced by the average con-
sumer would be required before signs of mercury intoxication would
appear.
The sources of mercury contamination in our environ-
ment are many and varied. Discharges from industrial plants into
rivers, incineration of mercury bearing trash, exhausts from metal
smelters, and crop applications put mercury into the air, soil, and
waterways. These sources are credited for an estimated one-third
of the yearly contribution, an additional one-third originates from com-
bustion of fossil fuels, and the remaining fraction originates from
natural sources. In soils, a reasonable background mercury concen-
tration would be between 10 and 150 ppb. The lakes, rivers, and
oceans are the primary method of transport for mercury in the environ-
ment with background levels of mercury in these waters typically rang-
ing from 0.02 to 0.7 ppb. Background atmospheric mercury concen-
3
trations vary between 0. 1 and 50 (J.g/m depending on urbanization.
Rainwater has been reported to contain 0. 05 to 0. 5 ppb mercury that
F-7
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results from scrubbing the atmosphere and is credited to man-
generated sources.
The hazard of mercury to man is primarily through the
methylation of inorganic mercury to organic mercury that takes place
principally in aquatic environments. Man's contribution to the total
accumulated environmental mercury pollution is less than 1 percent
except for local area concentrations. Although the contribution to the
worldwide mercury pollution has been little affected by man, over-
exposure to man-generated sources is the principal health hazard.
F.2.4 Other Elements
Additionally, adverse health effects have been observed
for the following elements (Ref. F-4). A short description of these
effects is given in the following listing:
a. Antimony - Toxic primarily as soluble compounds
causing injury to the heart, an increase in red blood
cells accompanied by a decrease in white cells, and
possible nervous system injury.
b. Arsenic - Arsenic toxicity is aggravated by its accumu-
lation within the body. Arsenic hazards are disputed,
but most evidence confirms its carcinogenic potential,
primarily to the skin.
c. Boron - Boron toxicity has been observed only as the
gaseous boranes or ingested as borates in heavy doses.
Primary symptom is nausea; very heavy doses are
required before boron compounds are lethal. Boron,
however, is toxic to a large variety of plant life,
many of which are included in man's diet.
d. Lead - Accumulates within the body as the result of
inhalation and ingestion. Lead poisoning is known to
cause brain damage, convulsions, behavior disorders,
and death. It has been most prevalent among children
as a consequence of their consumption of lead-bearing
paint chips.
e. Nickel - There is no evidence of nickel toxicity as an
element; however, as nickel carbonyl some evidence
exists that lung cancer can develop from inhalation.
F-8
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f. Selenium - Toxicity similar to arsenic; as hydrogen
selenide there exists some evidence for carcinogenic
reactions in test animals; when ingested in high doses
(significantly above natural mean background) evidence
exists for high incidence of dental caries.
g. Vanadium - Evidence exists for beneficial effects from
ingesting low concentrations of vanadium. Toxicity
effects are uncertain.
h. Zinc - Zinc is required as a nutrient in humans. Objec
tion to zinc as a "toxic" material is based primarily on
taste and appearance of drinking water containing low
concentrations.
F-9
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REFERENCES
F-l. Frank Princi, et al., Toxicity of Beryllium, ASD-TR-62-7-665,
University of Cincinnati, Ohio (April 1962).
F-2. Lars Friberg, et al. , Cadmium in the Environment, Chemical
Rubber Company Press, Cleveland, Ohio (1971).
F-3. F. M. D'ltri, The Environmental Mercury Problem, Chemical
Rubber Company Press, Cleveland, Ohio (1972).
F-4. "Trace Metals: Unknown, Unseen Pollution Threat," Chemical
and Engineering News (July 19, 1971).
F-10
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GLOSSARY
AA atomic absorption spectrophotometry
CPE chlorinated polyethylene
EPDM ethylene-propylene-terpolymer rubber
ES emission spectroscopy
IUCS International Utilities Conversion Systems, Inc.
JTU Jackson Turbidity Units
NERC National Environmental Research Center
PE polyethylene
ppb parts per billion
ppm parts per million
PVC poly vinyl chloride
SSMS spark source mass spectroscopy
TCA Turbulent Contact Absorber
TDS total dissolved solids
TVA Tennessee Valley Authority
USPHS United States Public Health Service
G-l
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TECHNICAL REPORT DATA
(Please rcatl litslfiiclions on llic reverse before completing)
I. HEPORT NO.
EPA-650/2-74-037-a
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Disposal of By-products from Non-regenerable
Flue Gas Desulfurization Systems: Initial Report
5. REPORT DATE
May 1974
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
J. Rossoff and R. C. Rossi
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
The Aerospace Corporation
Urban Programs Division
2350 El Segundo Boulevard, El Segundo, CA 90245
1AB013; ROAP 21ACX-AD
11. CONTRACT/GRANT NO.
68-02-1010
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
NERC-RTP, Control Systems Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Initial--11/72 - 12/73
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The report describes the initial phase of a study: to identify potential envi-
ronmental problems that may be associated with sludge disposal from non-regener-
able power plant flue gas desulfurization systems; to assess potential methods for
sludge disposal; to assess technologies and attendant economics for eliminating or
minimizing potential environmental problems related to sludge disposal; and to make
recommendations for sludge disposal. It includes the following results: laboratory
chemical and physical analyses of limestone sludges from two plants, one burning
eastern coal and the other, western; a review of power plant sludge production and
disposal plans; a survey of pond lining techniques and economics; technical and
economic surveys of sludge chemical fixation processes which treat the sludge to
produce a suitable landfill material; and a review of water quality and solid waste
management regulations.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Sludge
Sludge Disposal
Flue Gases «
Desulfurization
Economic Analysis
Analvsis
Physical Tests
Limestone
Coal
Ponds
Lining Processes
Earth Fills
Water Quality
Air Pollution Control
Stationary Sources
Pond Lining
Chemical Fixation
13B , 14B
7A
21D
21B, 8H
7D, 13H
5C, 13C
=1. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (Tliii Report)
Unclassified
21. NO. OF PAGES
318
20. SECURITY CLASS (This page I
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
H-l
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