United States
Environmental Protection
Industrial Environmental Research
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
  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).

  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.

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

    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
Environmental     Assessment      Economic      Character-
s' Assessment    & Development    Assessment      ization
  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
  5. Environmental Assessment of Coal
    Combustion Waste Disposal in Ocean
  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
 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
  1. FGC Waste By-Product Marketing
  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


U. S. Army - Dugway Proving         X
US. Army Corps of Engineers         X


Radian Corporation                X

TVA                            X

Bechtel National, Inc.

Radian Corporation












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
FGD Wastesc
110.1 (121.4)
"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

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
  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-
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
  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

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.

  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
   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
  Coal ash which  is not combined with
other wastes or marketed is usually dis-

Table 3.    Potential Disposal Options3

Wet Impoundments • Conventional
Gypsum Stacking
Dry Impoundment
Surface Mine
Underground Mine
At-sea Disposal
aSource: Arthur D. Little, Inc.
bC = Commercial Practice.
CP = Reasonable Potential.

Ash Waste

C6 C



 Table 4.    FGC Waste Generation by
           Industrial Boilers3

                  (106 metric tons)
             1980     1985     2000
Coal Ash
FGD Waste"
 "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
  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
  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-

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
  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-
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

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
  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-
  Biological    Absence of sensitive bio-
  Effects       logical resources.

Control Options
  Control options include dewatering,
stabilization, forced oxidation, and use of
  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
  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
  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
   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.


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.

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,


Air Pollution Control
and Disposal,


Disposal Only,
$/dry ton


Air Pollution Control
and Disposal,
$/dry ton


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.

                                                                   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
                                                                        . S. GOVERNMENT PRINTING OFFICE: 1983/659-095/1928

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