United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-83-007 Apr. 1983
Project Summary
Waste and Water Management
for Conventional Coal Combustion:
Assessment Report-1980
C. J. Santhanam, C. B. Cooper, A. A. Balasco, D. E. Kleinschmidt, I. Bodek, and
D. J. Hagerty
The report gives results of a study of
sintering and leaching mechanisms of
fly ash/spent sodium sorbent mixtures
from a dry injection flue gas desulfuri-
zation (FGD) process. It includes an
estimate of the economics of pelletizing
and sintering to handle the fly ash and
spent sorbent from a 500 MW power
plant burning low sulfur western coal
using a dry injection FGD process. The
process includes dual disc pelletizing
circu its and a furnace with an output of
nearly 717 tonnes/day of pellets sin-
tered to a temperature of 950-1000°G
In laboratory tests, pellets with fly ash
and either spent nahcolite or spent
trona (both reacted with SOa), when
thermally treated at 1000°C and mildly
stirred in water for 100 hrs, lost 30-60
percent of the total sulfur in the pellets
as SCfe evolved or SO4 leached. Under
similar conditions, 3-15 percent of the
available sodium leached. Encapsulat-
ing the dried pellets (or pellets fired at
925°C in concrete or asphalt mixes)
did not significantly inhibit the leaching
in water of the soluble alkaline su (fates
from the pellets. Cured concrete and
asphalt samples containing pellets on
a 20-percent-by-volume substitution
for limestone aggregate exhibited losses
in compressive strength of 50 and 75
percent respectively". Estimated capital
cost is $40.55/kW. The levelized annu-
al revenue requirement is nearly 4.92
mills/kWh.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory. Research Triangle
Park, NC, to announce key findings of
the research project that is fully doc-
umented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This report gives results of the assembly,
review, evaluation, and reporting of data
from research and development (R&D) as
well as commercial activities as of mid-
1980 in the areas of (1) flue gas cleaning
(FGC) waste disposal/utilization, and (2)
power plant water management including
recycle/treatment and reuse.
The purpose of these efforts was to
assist EPA in conducting an on-going R&D
program in these two areas. The full report
on this effort supplements a five-volume
1979 assessment report published early
in 1980[1].
This assessment focuses on:
• Evaluation of the technical, regulatory,
economic, and environmental aspects
of FGC waste disposal/utilization
with emphasis on the effects of these
factors on the feasibility and cost of
various disposal/utilization options.
Recommendations were made on
measures to fill information gaps,
including research to develop addi-
tional data
• Evaluation of the technical, regula-
tory, engineering/economic, and en-
vironmental aspects of power plant
water recycle/treatment/reuse Again,
recommendations were made to cover
gaps existing in 1980.
EPA's Waste and Water Program
Since 1974, the EPA has conducted an
on-going program of research on waste
and water management for coal-fired boilers.
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This program, referred to as a Waste and
Water Program, has had as its objective
the evaluation, development demonstra-
tion, and recommendation of environmen-
tally acceptable, cost-effective technology
for FGC waste disposal/utilization and
power plant water recycle/treatment/
reuse. EPA's Waste and Water Program
included five major areas, three of which
are within the scope of this report: FGC
waste disposal, FGC waste utilization,
water utilization/treatment, cooling tech-
nology, and waste heat utilization.
Waste and Water Program projects on-
going in 1980 are summarized in Table 1.
Those pertaining to cooling technology or
waste heat utilization, outside the scope of
this report, are not listed.
Background on Coal-Fired
Boilers
In 1980, more than 340 steam electric
plants in the U.S. utilized coal for 80% or
more of their power generation and had a
nameplate capacity >25 MW. During
1980-1995, 236 more new coal-fired
plants with a total generating capacity
>125,000 MW are anticipated. In addi-
tion, a number of plants are likely to be
converted to coal from other fossil fuels
(oil and gas).
As coal utilization in utility and large
industrial boilers increases, the quantity of
FGC wastes (i.e., coal ash and flue gas
desulfurization (FGD) wastes) will increase
dramatically. Most of these FGC wastes
will be disposed of. Over the longer term,
utilization is expected to grow but at a
slower rate than that of FGC waste genera-
tion. Table 2 projects coal ash and FGD
wastes through 1995 based on projections
of coal utilization, regulatory requirements,
and anticipated FGC practice. Several
factors will increase the sources and total
volume of waste and influence disposal
options in the coming year:
• An increase in coal-fired capacity in
the U.S. Total U.S. coal-fired electric
utility generating capactiy, estimated
at >191,000 MW in 1976, is ex-
pected to increase to>330,000 MW
by 1 988 [2,3].
Table 1. Ongoing Projects in EPA'S Water and Waste Program (1980)
Project Title
Contractor/Agency
Technology
Environmental Assessment Economic Character-
s' Assessment & Development Assessment ization
FGC WASTE DISPOSAL
7. Characterization and Environmental
Monitoring of Full-Scale Utility Waste
Disposal Sites
2. Assessment of Technology for Control
of Waste and Water Pollution
3. Disposal of By-Products from Non-
Regenerable FGD Systems
4. Dewatering of FGC Wastes by Gravity
Sedimentation
5. Environmental Assessment of Coal
Combustion Waste Disposal in Ocean
Waters
6. Evaluation of FGD Waste Disposal in
Mines and Ocean
7. Toxicity of Leachates
8. Ash Characterization and Disposal
9. Shawnee FGC Waste Disposal Field
Evaluation
10. Economics of Ash Disposal at Coal-
Fired Power Plants
11. Studies of Attenuation of Leachate
by Soils
12. FGC Waste Leachate/Liner Compati-
bility Studies
FGC WASTE UTILIZATION
1. FGC Waste By-Product Marketing
WATER UTILIZATION AND TREATMENT
1. Pilot-Scale Investigation of Closed-Loop
Ash Sluicing
2. Characterization of Effluents from Coat-
Fired Power Plants
3. Assessment of Various Technologies
for Treating Cooling Tower Slowdown
4. Feasibility of Ultrasonic and Other
Methods for Direct Measurement of
Condenser Biofouling
Arthur D. Little, Inc. X
Arthur D. Little, Inc. X
The Aerospace Corporation X
Auburn University
State University of New York X
at Stony Brook
Arthur D. Little, Inc. X
Oak Ridge National Laboratory
Tennessee Valley Authority X
TV A and Aerospace X
TVA
U. S. Army - Dugway Proving X
Ground
US. Army Corps of Engineers X
TVA
Radian Corporation X
TVA X
Bechtel National, Inc.
Radian Corporation
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
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Table 2. Projections of FGC Waste Generation by Utility Plants in the U.& (1980- 1995)a
Waste Generation, 106 metric tons/yr(106 tons/yrj
Waste Type
CoalAshb
FGD Wastesc
TOTAL
1980
62.4
8.6
71.0(78.3)
1985
83.2
26.9
110.1 (121.4)
1995
110.0
48.6
158.6(174.8)
"Source: Arthur D. Little, Inc. estimates.
bCoal ash quantities are on a dry basis.
CFGD waste Quantities are on a wet basis (50% solids).
• A major increase in the application of
FGD technology by utilities and a
consequent increase in FGD waste
generation. In 1980, > 27,000 MW
of generating capacity utilized FGD
systems, and> 95,000 MW of gross
generating capacity (approx. 72,000
MW scrubbed capacity) was com-
mitted (i.e., under construction con-
tract awards, or operating) to FGD
systems [4].
• Advances in commercial FGD waste
stabilization technology. These wastes
can be converted into moist soil-like
material by processes that usually
involve adding lime and fly ash. This
conversion permits landfill disposal
of partially dewatered solids. In the
future, disposal of wastes in managed
landfills (as opposed to ponds) is
likely to be encouraged.
• Environmental regulatory develop-
ments involving the Clean Air Act
Amendments of 1 977 and the Re-
source Conservation and Recovery
Act(RCRA).
Regulatory Considerations
Regulatory Overview
The disposal of FGC wastes is subject to
regulations at both Federal and state levels.
In 1980, FGC wastes were disposed of
exclusively on land. In the future, at-sea
disposal may be carried out to a limited
extent in regions with few available land
disposal sites.
Four major environmental issues con-
cern land disposal of wastes: waste stability/
consolidation, groundwater contamination,
surface water contamination, and fugitive
emissions.
These are regulated under the federal
legislative framework involving RCRA, the
Clean Air Act (CAA), Clean Water Act
(CWA), and other laws. RCRA is the major
federal environmental legislation aimed at
regulating disposal in landfills and im-
poundments.
Present Regulatory Framework
Since the publication of the 1979 as-
sessment report [1], the basic regulatory
framework governing water and waste
management for conventional coal com-
bustion has remained intact However, a
number of developments were expected
to have significant impact on how the
utilities and other industries deal with coal
combustion and. its waste streams.
The EPA, either directly or by delegation
to and oversight of state environmental
agencies, continued to have ultimate re-
sponsibility for the environmental regula-
tory aspects of water and waste manage-
ment EPA's Effluent Guidelines Division
issued revised proposed regulations for
the steam electric generating industry late
in 1980 [5]. These are particularly impor-
tant with respect to coal ash handling pro-
cedures and a number of water manage-
ment practices.
In the area of solid waste management
the EPA issued Final Regulations for classi-
fying (non-hazardous) disposal facilities in
September 1979; and for generators of
hazardous wastes, in May 1980 [6,7]. At
least 51 % of the solid wastes from con-
ventional coal combustion (i.e., fly ash,
bottom ash, and FGD waste) were explicitly
deferred from the coverage of the latter
regulations pending anticipated Congres-
sional action (Amendments to RCRA) and
further studies regarding the need for and
nature of appropriate controls. In October
1980, the anticipated Amendments to
RCRA were passed and studies (on utility
solid waste disposal practice) called for by
the RCRA Amendment were underway.
The EPA and other agencies also con-
tinued to issue other regulations affecting
the extent of generation and management
of coal and coal-combustion waste. In
1979-80, there was further work on NSPS
for gaseous and paniculate emissions [8],
and an increasing number of fuel switching
(i.e., oil and gas to coal) orders from the
Economic Regulatory Administration pur-
suant to the 1978 Fuel Use Act that can
add to FGC waste generation. In addition,
the Department of Interior (Office of
Surface Mining)~the primary agency con-
cerned with mine disposal of coal-related
wastes-further clarified aspects of (1)
non-coal waste disposal in surface mines,
and (2) its permanent regulatory program
for surface mining of coal. Both items are
relevant to the subjects covered in this
report Finally, additional activity occurred
in EPA's effort to implement Section
6002 of RCRA, which deals with guide-
lines for federal procurement of products
derived from recycled (e.g., waste) ma-
terials. Specifically, EPA addressed the
use of fly ash in concrete, with promulga-
tion of guidelines on federal procurement
expected in late 1980.
Water Management
Steam electric boilers rank second only
to agriculture in total water withdrawals
from national sources. Since most of this
water is for cooling and ash transport,
steam-electric power generation is the
largest direct discharger of water to surface
water bodies of any water-using sector.
Several studies on water management
were underway, sponsored by EPA EPRI,
and other organizations. The efforts
covered by this report focus on: (1) dry
handling technologies for FGC waste dis-
posal; (2) changes in cooling tower design,
operation, and maintenance practices to
minimize water intake and/or blowdown;
(3) biofouling control for condensers in
once-through cooling systems leading to
the reduction of use of some biofouling
agents; and (4) use of advanced tech-
nologies to prepare wastewaters for re-
cycling and reuse.
The trend toward dry fly ash handling
and disposal in new power plants appears
to be growing. Dry handling of fly ash
eliminates fly ash sluice water as a dis-
charge, and eliminates potentially complex
chemical problems connected with closed-
loop ash sluicing operations. Reportedly,
nearly half of the coal-fired power plants in
the U.S. could use dry handling methods
m-
Dry sorbent FGD systems are making
very substantial inroads affecting water
management by reducing the impact of
wet scrubbing FGD methods. As of late
1980, about 11 orders had been placed
for utility and industrial boiler applications
of dry sorbent systems [4], Side stream
water treatment of ash sluice water was to
be investigated on a pilot scale under an
EPA-sponsored effort
The cooling system is by far the largest
user and consumer of water in a power
plant. Work is underway to limit cooling
tower makeup and water pollution by
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limiting cooling tower blowdown. On the
other hand, projections of water shortages,
particularly in the West may encourage
dry orwel/dry hybrid systems. Therefore,
work is also underway to gain commercial
experience on wet/dry and dry cooling
towers with a goal of reduced water evap-
oration per kilowatt hour generated. It
appears that wet/dry cooling towers will
provide better performance and better
overall economics than fully dry cooling
systems. While the direct environmental
effects of dry and wet/dry systems are
low, greater energy requirements may
offset this advantage to some extent
Recycle and reuse of power plant waste
streams are generally undertaken to re-
duce water consumption and meet regula-
tory requirements. Two approaches to
water recycle/treatment reuse continue to
be emphasized: (1) coordination or cascad-
ing of effluent streams from plant process
units; and (2) application of treatment
techniques to allow water reuse, (usually
through recycle) which may not be other-
wise practicable. Method (1) involves the
hierarchy of water reuses, with waste from
one stream used as a feed to another to
utilize the water repeatedly prior to any
treatment, recycle, or discharge. Usually,
such methods do not require unconven-
tional equipment, but they do require
tighter operational controls and place
greater demands on skills of the operators.
Water treatment techniques may involve
additional technologies and can potentially
promote utilization of water within a water-
use hierarchy. Treatment can vary and
may utilize specialized technologies not
conventionally part of traditional power
plant water management To minimize
raw water consumption, some power
plants are using unconventional water
sources; e.g., secondary treated waste
water from sewage treatment plants.
Work is underway to limit the impact of
chlorination by shifting to minimum chlori-
nation practices. Alternative biocides(e.g.,
bromine chloride and chlorine dioxide) are
being investigated Dechlorination bySC>2
has been studied. Consideration of the
potential impacts of physical biofouling
systems is also underway. A number of
technologies (e.g., distillation, reverse
osmosis, and foam evaporation) were also
under investigation for treatment of various
side streams.
Generation of FGC Wastes
Ash Collection Technology
Coal-fired utility and industrial boilers
generate two types of coal ash—fly ash and
bottom ash. Fly ash, which accounts for
most of the ash generated, is the fine
fraction carried out of the boiler in the flue
gas. Bottom ash drops to the bottom of
the boiler and is collected either as boiler
slag or dry bottom ash, depending on the
type of boiler.
Collection of bottom ash (or boiler slag)
does not involve systems outside the
boiler. Fly ash, however, is a major source
of particulate emissions and (with regula-
tory requirements) has required major
collection systems. Control of particulate
emissions from pulverized-coal-fired steam
generators was rapidly becoming a sig-
nificant factor in the siting and public
acceptability of coal-burning power plants.
Typical methods of fly ash collection
include mechanical collection, electrostatic
precipitation, fabric filtration, and wet
scrubbing. However, only electrostatic
precipitators (ESPS) and bag filters can
meet the requirements in the foreseeable
future. A significant development over the
past few years has been the growing use
of bag filters and associated dry handling
methods, although ESPS still represent
most of the control equipment
FGD Technology
The implementation of FGD technology
on industrial and utility boilers is rapidly
growing in the U.S. As of June 1980, FGD
systems were in operation on >27,000
MW of utility generating capacity at some
73 differentunits[4]throughoutthe U.S.,
and more than 40 industrial steam plants
were equipped with FGD systems. The
degree of S02 control ranges from < 50%
S02 removal efficiency to >90%, depend-
ing on the type of FGD system, the sulfur
content of the fuel, and the applicable S02
emission regulations.
The growth in FGD systems over the
next 20 years will depend principally on
the growth in utility and industrial boiler
capacity, current and future SC"2 emissions
regulations, and the impact of alternative
desulfurization approaches (e.g., existing
and enhanced coal-cleaning techniques)
on current and developing FGD technology.
In general, FGD processes are designated
as either nonrecovery (throwaway) systems,
which produce a waste material for dis-
posal; or recovery systems, which produce
a saleable byproduct (either sulfur or sul-
furic acid) from the recovered S02. Non-
recovery processes make up the over-
whelming majority of the technology. Of
the 11 commercially available processes
and process variations, 8 are throwaway
systems. These eight constitute more
than 95% of the capacity in operation on
utility and industrial boilers, a trend which
was expected to continue for the foresee-
able future.
Disposal/Utilization
One of the most effective ways of man-
aging the FGC waste problem is to utilize
the coal ash and FGD wastes. A significant
fraction of the total generation of coal ash
is utilized. However, through 1980, there
had been no utilization of FGD wastes in
the U.S.; several studies on utilization
opportunities had been sponsored by the
EPA [1]. On balance, disposal will con-
tinue to be the major option for FGC waste
management in the U.S.
Several methods are potentially available
for the disposal of FGC wastes both on
land and at sea. Disposal options for FGC
can be broadly categorized on the basis of
the nature of the wastes and the type of
disposal. TableS lists potentially applicable
disposal options.
Disposal Technology for Industrial
Boiler FGC Wastes
An important development of the past
few years is the growing use of coal in
industrial boilers. Thus, management of
water and wastes associated with coal-
fired industrial boilers is expected to grow
in the future. Table 4 provides some esti-
mates on FGC waste generation by indus-
trial boilers.
The sodium throwaway process, used
more often than all other FGD systems
combined in industrial applications, pro-
duces a liquid waste stream. Common
practice is to discharge this stream to an
evaporation pond or to an existing water
treatment plant. The use of evaporation
ponds is more prevalent (most of these
systems are used on oil-field steam gene-
rators in California); however, this approach
is restricted to areas with adequate net
evaporation. Some sodium scrubbing sys-
tems (e.g., in paper mills and textile plants)
use a waste process stream containing
sodium as the scrubber feed. The waste is
then recombined with process waste
streams before discharge to a water treat-
ment plant Similarly, ammonia-containing
waste streams are also used as scrubber
feed.
FGD sludges from the lime/limestone
or dual alkali systems in industrial boilers
are disposed of in wet or dry impoundments.
Disposal methods include lined and unlined
ponding and landfilling. Treatment may
include dewatering, adding alkaline ash,
and/or applying commercial stabilization
technology.
Coal ash which is not combined with
other wastes or marketed is usually dis-
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Table 3. Potential Disposal Options3
Land
Wet Impoundments • Conventional
Gypsum Stacking
Dry Impoundment
Surface Mine
Underground Mine
At-sea Disposal
Shallow
Deep
aSource: Arthur D. Little, Inc.
bC = Commercial Practice.
CP = Reasonable Potential.
FGD
Ash Waste
C6 C
C C
C P
C P
P
P
Ash/FGD
Waste
Codisposal
C
P
C
C
P
P
P
Table 4. FGC Waste Generation by
Industrial Boilers3
(106 metric tons)
1980 1985 2000
Coal Ash
FGD Waste"
TOTAL
7.5
0.9
8.4
9.0
1.5
10.5
14.4
6.1
20.5
"Source: Arthur D. Little, Inc. estimates.
bFGD wastes are estimated on the base of cal-
cium-based wastes as 50% solids and sodium-
based solids as 5% dissolved solids by weight
posed of in landfills. FGC wastes from dry
sorbent FGD systems are also landfilled.
Trends in Industrial Boiler FGD
Wastes
The use of coal in industrial boilers is
expected to increase due to increasing
costs of oil and natural gas and the impact
of the Fuel Use Act. Emission standards
may also cause an increase in the use of
FGD systems and more efficient paniculate
control devices, which in turn would signi-
ficantly increase FGC waste generation.
Landfill disposal is expected to be en-
couraged over wet impoundment by regu-
latory and economic processes.
Waste disposal problems faced by in-
dustrial boiler operators differ from those
faced by utilities in several ways: (1)
industrial plants may be in urban areas
where little land is available for waste
disposal; (2) industrial operators may have
to hire contractors to dispose of FGD
waste; and (3) alternatively, emission stan-
dards may increase the number of small
landfills and ponds, introducing various
environmental control and management
problems.
As of 1 980, most research efforts had
concentrated on utility boilers. Information
was lacking in such areas as: (1) quantities
and properties of FGC wastes that will be
generated; (2) costs of treatment and
disposal to industries; and (3) environ-
mental effects of waste disposal alterna-
tives.
Characteristics of FGC Wastes
Chemical Characteristics
Much data on the chemical characteris-
tics of FGC wastes was published in
1979-80. Data were generated on various
constituents of FGC wastes, components
of leachates, and the relationship of chem-
ical properties to potential environmental
impact Modification of waste properties
by stabilization and of environmental im-
pact by soil attenuation were also studied.
Results from completed and ongoing
studies in this area are discussed below.
Radian studied chemical and physical
stability and properties of a variety of FGC
waste materials in an EPRI program. Fly
ash, unstabilized FGD, and stabilized FGD
waste materials were studied. Major and
trace elements were evaluated, major cry-
stalline phases identified, and leachability
of the elements explored. Estimates of
free lime in fly ash, obtained to indicate po-
tential self-hardening characteristics of
major crystalline phases in some FGC
waste samples using x-ray diffraction,
appear to indicate significant amounts of
amorphous material. In a slightly different
study, Rutgers University completed an
evaluation of the pozzolanic properties of
fly ash/limestone scrubber mixtures, using
solid state analytic techniques including x-
ray diffraction, differential scanning color-
imetry, and infrared spectrometry. Results
suggested that curing of stabilized samples
with and without air leads to different
products and that sulfite-type waste may
produce oxygen-free environments in a
disposal site.
TVA conducted laboratory studies on
coal ash leaching, examining characteris-
tics of ash, ash sluice water, leaching of
metals from various ashes, and effect of
pH adjustment on trace metal concentra-
tions in leachate. Ash fromfourTVA plants
was used. The study indicates that the
acidity or alkalinity of ash affects trace
element levels in ash sluice waters and
leachates. In another leaching study, the
U.S. Army Corps of Engineers' Waterways
Experiment Station (WES) completed a
series of column tests on stabilized FGC
wastes. In general, it appeared that lower
levels of most species occurred in elutriates
from stabilized materials.
The University of Notre Dame studied
the environmental effects, on groundwater,
of fly ash disposal in ponds from a large
coal-fired station. In a similar study at two
of their plants; TVA studied ash leachate,
groundwater, soil, fly ash, and bottom ash
to determine contamination by leachate
and attenuation by soils. Laboratory studies
on attenuation supplemented the effort.
WES completed a field study of disposal of
unstabilized FGC wastes at three sites.
Chemical analyses reportedly indicated
elevations of Fe, As, Cr, and Pb in the
groundwater from leachates.
The University of North Dakota continued
their mine disposal demonstration project
(initiated under EPA sponsorship and con-
tinuing under DOE sponsorship). The
data from this study seem to indicate that
North Dakota lignite fly ash produces leach-
ate that has potentially high concentra-
tions of As and Se, exceeding Primary
Drinking Water Standards by a maximum
factor of 1 2 and 80, respectively. Leach-
ates from FGD wastes (again, from the
same environs), exhibited much lower
metals values.
Much data was generated on the applica-
tion, to FGC wastes, of the proposed EPA
extraction procedure (EP); other informa-
tion on toxicity and radioactivity of FGC
wastes was also generated.
Physical Characteristics
Several studies on the physical and en-
gineering characteristics of FGC wastes
were underway in 1979-80. Some of the
more significant results are described below.
Studies by Radian compared FGC wastes
containing fly ash from Eastern bituminous
coals to those containing fly ash from
bituminous and lignite coals Unconfined
compression strength of some of the mix-
tures tested reached as high as 5,000 psi,
and increased with an increase in the
leachable alkalinity of the ashes. The
sulfite/sulfate ratio of the sludges used
apparently did not influence the value of
strength. The permeability of wastes
containing high calcium oxide (Western
coal) fly ash was 10-5 - 10'7 cm/sec. In
contrast, permeability of mixtures contain-
-------
ing low calcium oxide (Eastern coal) fly
ash generally was 10:4 - 10-6 cm/sec.
Research at Northwestern University on
waste management from double alkali
FGD systems provided information needed
for the design of methods of handling and
disposal of such FGD wastes in landfills.
Laboratory tests on the double alkali wastes
from FMC Corp.'s FGD process included
grain size analysis, specific gravity deter-
mination, Atterburg test limits, compac-
tion tests, compressibility tests, permea-
bility tests, and evaporation tests.
Studies on waste generated from a dry
sorbent FGC system at the University of
Tennessee included grain size distribution
of waste, specific gravity, compaction
characteristics of the waste, and uncon-
fined compression strength of the samples.
The stabilized wastes were also subject to
leaching tests using several techniques.
Tests on unconfined compression strength
indicate that the strength of the compacted
mixture of fly ash and dry FGD wastes
depends heavily on the mixed proportions
and the amount of unreacted lime present
It appears that if the proper proportion of
lime is present a relatively high-strength
landfill material can be obtained by com-
paction at optimum moisture content.
Utilization of Wastes
The utilization of fly ash, bottom ash,
and boiler slag steadily increased in the
1970s. In 1978, about 16.4 (of an annual
generation of 68.1) million metric tons
was utilized [9].
The principal uses for fly ash appeared
to be in the pozzolan market (in cement
and concrete) and accounted for about 2.1
of the 8.4 million tons of fly ash utilized.
Other major uses of fly ash include as a
filler material for roads and construction,
and as a stabilizer for road bases. The
largest amount of fly ash was, however,
disposed of. Additionally, in recent years a
fast growing use for fly ash has been in the
stabilization of FGD wastes. This is tech-
nically considered to be "disposal;" al-
though, if the stabilized waste is used as a
road construction base or in some other
analogous application, it may be considered
"utilization."
Bottom ash and boiler slag utilization
continued at about the same level as in
1977-78. The largest end uses were for
bottom ash as a fill material, as a filler in
asphalt for ice control, as a blasting grit or
as roofing granules. Boiler slag was also
growing in utilization, although somewhat
erratically. The principal use of boiler slag
was in deicing roads and bridges.
On balance, these utilization trends are
expected to continue, at least through
1985. Total ash collection is increasing
dramatically; therefore, the amount of FGC
wastes sent to disposal is likely to increase
over the next few years.
Disposal of FGC Wastes
Current Practice
In 1980, all FGC wastes were disposed
of on land. At-sea disposal may be a future
alternative if it can be practiced under
environmentally acceptable conditions. The
principal methods of disposal are: ponding;
landfilling, including mine disposal; and
interim ponding followed by landfilling.
At-sea disposal of FGD wastes was not
practiced in the U.S. in 1980. However, if
it could be practiced under environmentally
acceptable conditions, it would represent
an important option, particularly along the
East Coast where land for disposal is
limited. For this and other reasons, EPA
and others have been studying the dis-
posal of FGD wastes at sea.
Wet Ponding
Ponding is more widely used than any
other disposal method; it can be used for a
wide variety of FGC wastes. Ponds can be
designed based on diking or excavation
and can even be engineered on slopes.
A special case of wet ponding is FGD
gypsum stacking, which was under evalu-
ation in 1980. Inthiscase, if the operation
were analogous to that for phos-gypsum,
FGD gypsum slurry (typically from forced
oxidation systems) would be piped to a
pond, allowed to settle, and the supernate
recycled. Periodically the gypsum would
be dredged and stacked around the em-
bankment thus building up the embank-
ment
Dry Impoundment
Dry impoundment may include: (1)
interim ponding followed by dewatering
(or excavation) and landfilling; (2) mech-
anical dewatering and landfilling of FGD
wastes; (3) blending of FGD waste with fly
ash and landfilling of the combined wastes;
and (4) stabilization through the use of
additives (nonproprietary or otherwise).
Typically, for dry-impoundment disposal,
the wastes are thickened and dewatered
to a high solids content (FGD waste may
also be mixed with fly ash). This material is
transported to the disposal site where it is
spread on the ground in about 0.3 - 1 m
(1 -3 ft) lifts and compacted by wide track
dozers, heavy rollers, or other equipment
A properly designed and operated dry
impoundment system can potentially en-
hance the value of the disposal site after
termination or at least permit post-opera-
tional use.
Mine Disposal
Ash disposal in mines has been practiced
for several years, particularly in the Western
U.S. Coal mines, in particular surface area
coal mines, are the most likely candidates
for waste disposal.
Coal mines offer the greatest capacity
for disposal, and they frequently are tied
directly to power plants. In fact many new
coal-fired power plants are mine-mouth
(located within a few miles of the mine),
and the mine provides a dedicated coal
supply.
Field Studies
In 1980, several field studies were
underway to evaluate various methods of
land disposal of FGC wastes. Features of
the major studies are described below.
A large EPA-sponsored project on char-
acterization and environmental evaluation
of six full-scale utility waste disposal sites
by Arthur D. Little, Inc., started in late
1979 and was well underway in 1980.
This study is expected to provide substan-
tial information concerning the degree
to which disposal of FGC wastes needs to
be managed to protect the environment
A similar EPRI-sponsored study at a
single site (Columbus and Southern Ohio
Electrics Conesville Plant) with Michael
Baker and Battelle-Columbus was contin-
uing in 1980. Interim reports on monitor-
ing of the Conesville site and modeling of
associated groundwater had led to some
preliminary conclusions on field versus
laboratory permeablity of stabilized FGD
wastes. EPRI was also funding an eight-
site study by Michael Baker to focus on
the engineering/economic assessment of
FGC waste disposal. This study was ex-
pected to provide substantial data by late
1981.
Studies continued at TVA's Shawnee
Plant by Aerospace (under EPA sponsor-
ship) concerning disposal methods, im-
pacts of weathering, soil interactions and
field operational procedures. Investigators
report that if untreated sludge is properly
drained, it can be structurally sound and
support significant surface loading. Simi-
larly, properly dewatered gypsum also
exhibited significant bearing strength.
Preliminary results from the mine dis-
posal of lignite fly ash and FGD waste in
North Dakota seemed to indicate that both
wastes can impact the groundwater due to
the amounts of soluble sulfate salts. It
appears that placing FGD wastes in mined
areas can be an effective means of dispos-
ing of this waste if careful attention is paid
to site selection and design/operation of
the FGC disposal systems.
-------
State University of New York (SUNY) at
Stony Brook continued a program to assess
the feasibility of disposing of blocks of
stabilized FGC wastes at sea to produce
artificial reefs. Preliminary test results
indicated that blocks undergo no appreci-
able degradation by dissolution during 1.5
years in seawater.
Present Control Technology
The environmental impact of FGC waste
disposal (hence, any potential impacts on
human health and environment) is influ-
enced by: (1) type of waste generated (i. e.,
physical and chemical characteristics); (2)
disposal method used (e.g., ponding, land-
filling); and (3) disposal site characteristics
(e.g., soil type, hydrogeology, climate).
It is expected that much of the difference
between potential and actual impacts for
the FGC waste disposal options discussed
above will be determined by the degree to
which presently available control tech-
nology is incorporated as "good design"
and "good practice" in typical disposal
operations. Good design and practice
could also minimize the potential for ad-
verse impact from abnormal events.
Site Selection
Site selection may or may not be con-
sidered control technology. However, there
is no question that proper site selection
could by itself ameliorate or eliminate
most of the potential disposal impacts.
The following mitigative combinations of
site characteristics and impact issue cate-
gories are considered applicable:
Potential Mitigative Site
Impact Issue Characteristics
Land Use Proper topography, ge-
ology, and hydrology;
absence of nearby con-
flicting land uses.
Water Quality As above for land use,
plus absence of nearby
sensitive receiving waters
(e.g., a small stream or
very pure aquifier).
Air Quality Absence of "non-attain-
ment area" and Class I
Prevention of Significant
Deterioration designations
for total suspended par-
ticulates.
Biological Absence of sensitive bio-
Effects logical resources.
Control Options
Control options include dewatering,
stabilization, forced oxidation, and use of
liners.
As discussed earlier, dewatering of FGC
waste prior to processing or land disposal
can result in major improvements in physi-
cal stability and reduce water quality im-
pacts regardless of the disposal approach
used.
Stabilization refers to groups of pro-
cesses to obtain easy-to-handle materials
from difficult-to-handle and difficult-to-
dewater FGD wastes. Major processes in
use are: (1) processes such as Conversion
Systems, Ina's, based on adding lime and
fly ash to FGD wastes to obtain a moist
soil-like waste for land disposal; (2) pro-
cesses based on proprietary additives,
such as Dravo's Calcilox, to obtain a stable
waste in water; and (3) inherent stabiliza-
tion of alkaline fly ash/FGD wastes by the
fly ash itself.
In October 1980, at least 25 U.S. utility
operators were committed to some type of
stabilization process [1].
The intentional production of sulfate-
rich wastes or gypsum, rather than sulfite-
rich FGC wastes, was subject of consider-
able interest in 1980. This was primarily
due to the relative ease in dewatering
gypsum, which alleviates the handling
difficulties associated with sulfite-rich
wastes.
Liners may not be required for FGC
waste disposal except under certain site
specific conditions. Field experience with
liners for FGC waste disposal was limited
in 1980, but ongoing and recently an-
nounced programs were expected to close
this gap.
Disposal Economics
The economics of FGC waste disposal
continued to be an important factor in
implementing paniculate and S02 control.
Several conceptual design and cost studies
on waste disposal had been undertaken,
sponsored by both government agencies
and private organizations—notably EPA,
EPRI, and DOE. These studies focused on
developing comparative economics for
various wastes (coal ash and FGD) for
various waste disposal options, including
current practices and potential alternatives.
In addition to these studies, a major on-
going study, sponsored by the EPA, in-
volved a characterization and environ-
mental evaluation program at utility solid
waste (coal ash and FGD) disposal sites.
Total capital and annual operating costs
for waste disposal were to be developed
for each site.
As an overview of the individual studies,
costs for eight of the more important types
of waste disposal are summarized in Table
5. For each process, basic assumptions
allowed comparison of the capital and
revenue requirements developed.
Figure 1 briefly describes the eight
methods.
Even with these waste disposal cost
studies, data gaps remained in 1980 on
the economics of the disposal of FGC
wastes, including both cost information,
and knowledge of waste properties and
disposal requirements that directly impact
disposal costs. The most important of
these are:
• A general lack of uniformity in basic
cost assumptions in the studies.
• A general lack of reliable cost infor-
mation from commercial operations
of most types of FGC waste disposal.
Ongoing and planned EPA projects
were expected to at least partially fill
this gap.
• No definitive studies on the disposal
of wastes from dry sorbent systems
and associated costs.
• Inadequate physical and engineering
properties data on some types of
wastes as a basis for developing
design requirements needed for reli-
able estimates of cost-effective dis-
posal systems.
References
1. Santhanam, C.J., et al., "Waste and
Water Management for Conventional
Combustion: Assessment Report 1979,"
Arthur D. Little, Inc.:
Vol.l -Executive Summary, EPA-600
77-80-012a (NTIS PB80-158
884), January 1980.
Vol. II -Water Management, EPA-600
77-80-012b(NTIS PB80-185
564), March 1980.
Vol. Ill -Generation and Characteriza-
tion of FGC Wastes, EPA-600
77-80-012c (NTIS PB 80-222
409), March 1980.
Vol. IV-Utilization of FGC Wastes, EPA
-600/7-80-012d (NTIS PB 80
-184765), March 1980.
Vol. V -Disposal of FGC Wastes, EPA-
600/7-80-012e(NTIS PB 80-
185572), March 1980.
2. NERC, "National Electric Reliability
Council 75th Annual Review of Overall
Reliability and Adequacy of the North
American Power System", Princeton,
NJ, 1977.
3. National Coal Association, "1979 Sur-
vey of Electric Utility Capacity Additions,
1979-1988", Washington, DC, De-
cember 1979.
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Table 5. Engineering Economics of FGC Waste Disposal
Annual Revenue Requirements
Capital Costs (mid-1980 dollars)3 (mid-1981 dollars)3
Disposal Method
Untreated Ponding1*
Dravo Calcilox Pondingb
Dravo Calcilox Landfilling0
Lime & Fly Ash Stabilization/
Landfilling (lUCSp
Untreated FGD Sludge ft Fly Ash
Blending/ Landfillingc
Gypsum (forced oxidation)/ Landfilling'1
Alkaline Ash Wastes/ Mine Disposal11
Fly Ash/Landfillinge
Disposal Only,
$/kW
38.0
53.0
22.0
23.0
19.0
12.0
18.0
2.0
Air Pollution Control
and Disposal,
$/kW
117.0
132.0
122.0
124.0
119.0
96.0
97.0
23.0
Disposal Only,
$/dry ton
9.0
17.0
13.0
14.0
10.0
9.0
9.0
6.0
Air Pollution Control
and Disposal,
$/dry ton
41.0
47.0
49.0
50.0
47.0
46.0
41.0
19.0
3Basic Assumptions: Power Plant-500 MW boiler, 9000 Btu/kWh heat rate, Midwestern location, 30-year service life, 80% load factor (1st 10 years),
48% lifetime average load factor, 1 mi from plant to disposal site.
Coal Properties-3.5% S, 16% ash, 10,500 Btu/lb heating value.
Scrubber System-limestone (except for alkaline ash/mine disposal), 1.5 stoichiometry for conventional limestone, 1.1
stoichiometry for forced oxidation, SO2 emissions controlled to 1.2 lb/106 Btu.
Capital Charge Factor-0.164.
''Includes costs of scrubber (simultaneous fly ash and SO2 removal).
cIncludes costs of scrubber and ESP (for separate fly ash collect/on).
^Includes costs of scrubber (simultaneous fly ash and SO2 removal) and air oxidation modifications.
eIncludes costs of ESP.
4. Smith, M., et al., "EPA Utility FGD
Survey - January-March 1980",
EPA-600/7-80-029b (NTIS PB 80-
211832), PEDCo Environmental, Inc.,
May 1980.
5. U.S. EPA "Effluent Limitation Guide-
lines Pretreatment Standards and New
Source Performance Standards under
the Clean Water Act - Steam Electric
Generating Point Source Category",
Federal Register, Tuesday, October 14,
1980, pp. 68328-68356.
6. U.S. EPA, "Criteria for Classification of
Solid Waste Disposal Facilities and Prac-
tices, Final, Interim Final, and Proposed
Regulations", Federal Register, Part IX,
September 1 3, 1 979.
7. U.S. EPA, "Hazardous Waste Manage-
ment System", Federal Register, May
19, 1980.
8. "New Source Performance Standards -
Electric Utility Steam Generating Units",
Federal Register, Vol. 44, No. 113, pp.
33580-33624, Monday, June 1979.
9. National Ash Association, Washington,
DC, "Ash at Work", Vol. XI, No. 2,1979.
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Untreated
J Landfill \_
Figure 1. FGC waste disposal methods.
-------
C. J. Santhanam, C.B. Cooper, A. A. Balasco, D. E. Kleinschmidt, and I. Bodek are
with Arthur D, Little. Inc.. Cambridge. MA 02140; D. J. Hagerty is with the
University of Louisville. Louisville, KY 40208.
Julian W. Jones is the EPA Project Officer (see below).
The complete report, entitled "Waste and Water Management for Conventional
Coal Combustion: A ssessment Report - 1 980," (Order No. PB 83-163154; Cost:
$55.00. subject to change} will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
10
. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/1928
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