EPA-650/2-75-010-0.
April 1975
Environmental Protection Technology Series
.V.VV.V.'.'.V.V
Sr1»
I
35
o
UJ %
yf^y^^^^^^^^^j^
-------
EPA-650/2-75-010-0
SULFUR OXIDE
THROWAWAY SLUDGE
EVALUATION PANEL (SOTSEP),
VOLUME I:
FINAL REPORT - EXECUTIVE SUMMARY
Frank T. Pnnciotta
SOTSEP Chairman
Control Systems Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina 27711
ROAPNo. 21ACY-030
Program Element No. 1AB013
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, N. C. 27711
April 1975
-------
EPA REVIEW NOTICE
This report has been reviewed by EPA and approved for publication.
Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S. Environ-
mental Protection Agency, have'been grouped into series. These broad
categories were established to facilitate further development and applica-
tion of environmental technology. Elimination of traditional grouping was
consciously planned to foster technology transfer and maximum interface
in related fields. These series are:
1. ENVIRONMENTAL HEALTH EFFECTS RESEARCH
2. ENVIRONMENTAL PROTECTION TECHNOLOGY
3. ECOLOGICAL RESEARCH
4. ENVIRONMENTAL MONITORING
5. SOC1OECONOMIC ENVIRONMENTAL STUDIES
6. SCIENTIFIC AND TECHNICAL ASSESSMENT REPORTS
9. MISCELLANEOUS
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent environmental degradation from point and non-
point sources of pollution. This work provides the new or improved
technology required for the control and treatment of pollution sources
to meet environmental quality standards.
This document is available to the public for sale through the National
Technical Information Service. Springfield, Virginia 22161.
Publication No. EPA-650/2-75-010-a
11
-------
TABLE OF CONTENTS
PAGE
Vol.1 Vol.II
LIST OF TABLES v . , v
LIST OF FIGURES vi .. xii
FOREWORD vii . . xiv
ACKNOWLEDGEMENTS xi , xviii
METRIC CONVERSION FACTORS xii . . xix
FINDINGS 1 .. --
TECHNICAL RECOMMENDATIONS 13 . . --
TECHNICAL DISCUSSION SUMMARY 17 . . --
I. DEFINITION OF THE PROBLEM 17 . . 1
A. Availability of Alternative SOV
A
Control Technology 17 . . 1
B. Potential Demand for Lime/Limestone
Scrubbing 22 . . 39
C. Quantification of the Problem and
Comparison with Analagous Environ-
mental Problems 24 . . 55
D. Relationship Between Sulfur Oxide
Scrubber Sludge, Standards/Regulations,
and Enforcement 34 . . 70
E. Nature of the Material 36 . , 75
F. References -- .. 112
II. APPROACHES TO DISPOSING OF OR UTILIZING
SCRUBBER SLUDGE MATERIALS 40 , . 121
A. Commercial Utilization 40 . , 121
B. Present and Planned Utility Industry
Disposal Programs 41 . . 132
iii
-------
TABLE OF CONTENTS (Continued)
PAGE
Vol.1 Vol.II
II. C. Disposal by Ponding 45 . . 147
D. Disposal by Landfill 47 . . 169
E. Other Disposal Methods 49 . . 226
F. Current EPA R&D Programs 50 . . 228
G. References -- .. 236
III. ALTERNATIVE SULFUR BY-PRODUCTS 54 . . 245
A. Production Technology — . . 245
B. Economic and Marketing Considerations — .. 249
C. Environmental Considerations -- . . 270
D. Economic and Environmental Comparison
with Sludge -- . . 275
E. References -- .. 281
IV
-------
TABLES
Title Page
1 Economic Estimates for S02 Control Alternatives
(1974 Dollars) 19
2 Typical Quantities of Ash and Sludge Produced by
a 1000 Mw Coal-Fired Generating Station Con-
trolled with Lime/Limestone Flue Gas Desulfuriza-
tion Systems, Short Tons Per Year 26
3 Comparative Land and Solid Waste Impact of 1,000
Mw Electric Energy System (0.75 Load Factor)
(Low Levels of Environmental Controls Except for
Installation of a Limestone FGD System for SOX
and Particulate Removal) 28
4 Comparison of Major Solid Waste Disposal Problems . 29
5 Sludge Treatment/Disposal Techniques for Selected
Utility Lime/Limestone FGD Systems 42
6 Comparison of Economic, Marketing, >and Disposal
Aspects of Flue Gas Cleaning By-Products 56
-------
FIGURES
Figure
No. Title Page
1 Process Cost Comparison for Nonregenerable
and Regenerable Flue Gas Desulfurization
Systems--Effect of Sludge Disposal and By-
Product Sales or Disposal (Without Fly Ash) 20
2 Cumulative Need: FGD for Coal-Fired Power
Plants 23
vi
-------
FOREWORD
This report by EPA's Sulfur Oxide Throwaway Sludge
Evaluation Panel (SOTSEP) presents the results of an intermedia
evaluation of the environmental and economic factors associated
with disposal or utilization of sludge from nonregenerable flue
gas desulfurization processes. The evaluation was conducted
in the context of alternate sulfur oxide control techniques;
existing and anticipated air, solid waste, and water standards;
and other factors which might have a major influence on the
potential generation of sludge, its disposal, and the magnitude
of any potential environmental problems associated with its
disposal.
The SOTSEP consisted of the following EPA members who
participated in panel activities and co-authored the report:
Frank Princiotta (Chairman) - Office of Research
and Development (ORD), National Environmental
Research Center-Research Triangle Park (NERC-RTP),
Control Systems Laboratory (CSL), Gas Cleaning
and Metallurgical Processes Branch (GCMPB)
Arnold Goldberg - ORD, Air Pollution Control
Division (APCD)
Julian Jones - ORD, NERC-RTP, CSL, GCMPB
William Schofield - ORD, NERC-RTP, CSL, Engineering
Analysis Branch (EAB)
vii
-------
Richard Stern - ORD, NERC-RTP,. CSL, GCMPB
Robert Walsh - Office of Air and Waste Management
(OAWM), Emission Standards and Engineering Division
(ESED), Office of Control Technology (OCT)
In addition to the above air pollution technology
oriented members, the panel included water and solid waste
pollution technology oriented associate members who actively
participated in a consulting role and supplied inputs for the
report:
Alden Christiansen - ORD, NERC-Corvallis, Thermal
Pollution Research Programs (TPRP)
Robert Dean - ORD, NERC-Cincinnati, Advanced Waste
Treatment Research Laboratory (AWTRL), Ultimate
Disposal Research Program (UDRP)
Ronald Hill - ORD, NERC-Cincinnati, AWTRL, Mine
Drainage Pollution Control Activities (MDPCA)
Jack Keeley - ORD, NERC-Corvallis, Robert S. Kerr
Environmental Research Laboratory, Ground Water
Research (GWR)
Norbert Schomaker - ORD, NERC-Cincinnati, Solid
and Hazardous Waste Research Laboratory (SHWRL),
Disposal Technology Branch (DTB)
The results of the SOTSEP activity are presented in
two separate volumes each covering the following general
categories:-
viii
-------
Definition of the problem - status of
alternative sulfur oxide control tech-
nology, potential demand for lime/
limestone scrubbing, quantification of
the problem and comparison with analogous
environmental problems, impact of SO
A
scrubber sludge relative to current and
proposed regulation/enforcement, and
nature of the material.
Approaches to disposing of or utilizing
scrubber sludge materials - commercial
utilization, current and planned industry
disposal, disposal by ponding, disposal
by landfill, other disposal, and current
EPA R&D programs.
Alternative sulfur by-products - tech-
nologies for production, economic and
marketing considerations for elemental
sulfur, sulfuric acid, gypsum, sodium
sulfate, ammonium sulfate, and liquid
SO2, environmental considerations, and
economic and environmental comparison
with scrubber sludge.
Volume I, the Executive Summary, presents the panel
findings and technical recommendations, followed by a Technical
Discussion Summary which provides further details in each
specific category of study.
Volume II, the Technical Discussion, provides a compre-
hensive discussion of each specific area of study and supplies
ix
-------
back-up information and references for the Volume I Technical
Discussion Summary.
Because of time constraints, SOTSEP activities were
streamlined by working in accordance with the following
groundrules:
1. The scope of the activities focused
primarily on SO and particulate
a
control for coal-burning power plant
emissions. The flue gas desulfuriza-
tion process was assumed to operate
in a closed-loop with no direct dis-
charge; liquor leaves the system only
by evaporative losses in the scrubber
and by inclusion with the sludge.
2. The study assumed that there would be
no major deviations from either the
Clean Air Amendments of 1970 or EPA's
present implementation policies,
through 19.80.
3. Readily available information was
utilized to the maximum possible
extent.
4. Current CSL contractors were utilized
to the maximum possible extent.
-------
ACKNOWLEDGEMENTS
Appreciation is acknowledged for the timely and
responsive assistance of the following:
Radian Corporation which accumulated
and evaluated a major portion of infor-
mation, provided an early draft version
of the Technical Discussion, and assisted
in preparation of the final version of
the report.
Aerospace Corporation which supplied
scrubber sludge utilization information
and chemical and physical property data,
and assisted in review of the Executive
Summary.
CSL secretaries Carolyn Fowler, Charlotte
Bercegeay, Virginia Purefoy, Linda DeVinney,
Gloria Rigsbee, Lynn Pendergraft, and
Theresa Butts.
xi
-------
METRIC CONVERSION FACTORS
In compliance with EPA policy, metric units have
been used extensively in this report (followed by British units
in parentheses). However, in some cases, British units have
been used for ease of comprehension. For these cases, the
following conversion table is provided:
British
Metric
1 Btu
1 Btu
5/9 (°F-32)
1 ft
1 ft2
1 ft3
1 yd
1 yd2
1 yd3
1 mile
1 mile2
1 acre
1 pound
1 ton (short)
252 calories
2.93 x 10"" kilowatt-hours
°C
0.3048 meter
0.0929 meters2
0.0283 meters3
0.9144 meters
0.8361 meters2
0.7646 meters3
1.609 kilometers
2.59 kilometers2
4047 meters2
0.4536 kilograms
0.9072 metric tons
xii
-------
FINDINGS
Assessment of the available information by SOTSEP
members and associate members has resulted in the following
general finding:
Lime/limestone scrubbing, with controlled
disposal of scrubber sludge^ is an environ-
mentally acceptable approach to near-term
flue gas pollutant control. Although the
total environmental impact associated with
disposal of untreated sludge in a soil-lined
disposal area is not completely defined,
currently available technology appears to be
capable of environmentally acceptable dis-
posal. A high degree of confidence in elim-
inating potential secondary pollution effects
can be achieved with a combined approach
incorporating pond lining and chemical treat-
ment (fixation). On the other hand, health
effects data on air pollutants (notably
sulfur compounds) sufficiently indicate the
hazards of their emission. Consequently,
prevention of these emissions with subsequent
containment of air pollutants and controlled
disposal is clearly preferred over uncon-
trolled emission into the atmosphere.
The specific findings which follow are related to each
of the three major study categories. Additional specific
Regenerable flue gas desulfurization processes (i.e., those
producing sulfuric acid or elemental sulfur) do not produce
sludge as a waste product.
-------
findings are included in a fourth category which summarizes the
key findings relevant to technical recommendations.
I. DEFINITION OF THE PROBLEM
1. Based on a review of SOV control technologies,
A
installation of flue gas desulfurization (FGD) systems on units
burning high-sulfur coal is the major alternative to scarce
clean fuels which can be commercially available between now
and 1980. Other technological alternatives such as .coal gas-
ification, coal liquefaction, and advanced combustion processes
are not expected to make a significant contribution to clean
fuel availability until after 1980. Based on current trends,
technology availability, qualified system suppliers, and lead
time considerations, the majority of FGD system installations
through 1980 will be lime/limestone wet scrubbing processes.
2. Installation of FGD systems is presently demand-
limited; regulatory pressures are expected to change this to a
supply-limited situation sometime between 1975 and 1977 which
will continue through about 1980. Under these conditions, it
is estimated that FGD control will most likely be installed on
90,000 Mw or about 35% of total estimated coal-fired utility
generating capacity by 1980. High-sulfur oil-fired utility
plants, high-sulfur coal-fired industrial boilers, and other
sources such as smelters and acid plants are not included.
Most of the 90,000 Mw capacity is expected to be controlled by
lime/limestone wet scrubbing systems producing a throwaway
sludge. Assuming all of the installations to be lime/limestone
systems* 119,000,000 metric tons/year (131,000,000 tons/year)
It is unlikely that all the coal-fired utility FGD installa-
tions will be lime/limestone systems. However, the majority
are expected to be, and other applications (e.g., oil-fired
utility boilers, coal-fired industrial boilers) could make the
projected production figure quite realistic.
-2-
-------
of wet* limestone sludge including ash, or 108,000,000 metric
tons (119,000,000 tons) of wet lime sludge including ash, will
be produced in 1980. If projected viability and availability
of alternative clean-fuel technologies does not materialize,
annual sludge production could be substantially higher in the
post-1980 period.
3. Several types of dry solid and sludge wastes other
than those produced by FGD processes, many of which contain
potentially hazardous constituents, have been generated in great
quantities and disposed of by ponding or landfill for many years.
Although some of the problems associated with disposal of non-
FGD wastes are not completely resolved, techniques have been
developed which provide varying degrees of environmental
protection.
4. To place scrubber sludge in quantitative perspec-
tive, three comparisons are presented:
a. Approximate rates of solid waste production
for a typical 1000 Mw coal-fired power plant:
Production Rate. 10' Short Tons/Year
Waste
Deep Mining Wastes (Coal)
Surface Mining Wastes (Coal)
Dry Basis Wet Basts
94.2 97.1 (971 solids) (in addition. 6.205 x 10' tons of
acid mine drainage sludge)
2707 2762 (98% solids) (in addition, 0.328 x 10' tons of
acid mine drainage sludge)
Processing Wastes
Scrubber Sludge (exclusive of ash)a
Coal Ash"
Total Wastes, Deep Mining Case
Total Wastes, Surface Mining Case
450
392
338
1274
3887
454 (99% solids)
784 (SOX solids)
a. 423 (80% solids) (ash collected In different
pond than scrubber sludge)
b 676 (50% solids) (fly ash collected in scrubber
and sluiced to same pond as bottom ash)
2011b
4676b
"For 3.0% S, 12% ash, 6400 hrs/yr, limestone scrubbing, 85% SOj removal. 100% ash removal.
CaCOi to S02 mole ratio is 1.20.
For coal ash collection method b.
'Unless otherwise specified, sludge tonnage is on a wet (50%
solids) basis including ash.
-3-
-------
b. Associated land usage for a typical 1000 Mw
coal-fired power plant:
Item
Surface Mining
Processing
Rail Transport
Plant Site
Plant Site Waste
(combustion and
pollution control)
Transmission Lines
Distribution of Land
Usage with Limestone FGD
for S02 and Particulate,
Ponded Untreated Sludge
40.9%
0.5
6.5
1.0
Distribution of Land
Usage with Particulate
Control Only. Ponded Ash
41.2%
0.5
6.4
1.0
1.1 (sludge incl. ash)
50.0
100.0%
(Total of 34,289 acres)
0.3 (ash only)
50.6
100.0%
(Total of 34,021 acres)
It may be seen that land usage related to plant site
wastes is a small fraction of total land usage. However, it
should be noted that the environmental impact of each individual
usage varies considerably, requiring consideration of many
factors other than the relative areas involved.
c. Comparison with other sources of solid waste:
The comparison of projected levels of scrubber
sludge with the quantities of solid waste generated by other
industries provides a means of placing sludge disposal into
proper perspective. The following table summarizes the quantities
of waste material produced by several typical industries and
compares* existing and projected levels of waste requiring dis-
posal with 1980 projections of scrubber sludge. All figures
are on an "as disposed" basis.
-4-
-------
Waste Material Wt 1, Solids
Mineral Ore Wastes
Taconite Tailings
Phosphate Rock Slime
Municipal and Industrial
Refuse
Coal Ash
Culm Piles
Limestone Scrubber
Sludge
Municipal Sewage Sludge
Gypsum from Fertilizer
Manufacturer
Acid Mine Drainage Sludge
100
4-b
4-6
75
SO
100
50
0.1-20
85-90
1-5
"As Disposed" Quantity, 10 6 Metric
Tons/Year (Reference Year)
1300
1100
760
360
95
>91
64
55
28
8.2
(1970)
(1971)
(1970)
(1973)
(1980)
(1969)
(1980)
(1980)
(1973)
(1973)
5. To place scrubber sludge in qualitative per-
spective, the following comparison with coal ash is presented:
a. Although the detailed composition of sludges
will vary somewhat from system to system, the major constituents
are generally calcium sulfite (CaS03-%H20), calcium sulfate
(CaSO., • 2H20), calcium carbonate (CaC03), and unreacted lime
(CaO). Depending on the physical layout of the total emissions
control system, more or less fly ash is associated with the
sludge. The major constituents in fly ash are silica (Si02),
alumina (A1203), and ferric oxide (Fe203) in discrete and mixed
compounds. The calcium compounds have a limited solubility
in sludge liquors. The major components in fly ash are even
less soluble.
b. Sludge solids will also contain trace ele-
ments and other species originating in the coal, limestone or
-5-
-------
lime, and make-up water. The primary source of trace elements
is the coal. Ash solids will also contain trace elements and
other species originating in the coal and ash sluice water.
c. Sludge and ash liquors will contain dissolved
solids up to the solubility limits of individual species. The
solubilities are highly pH dependent with the general trend of
increasing solubility with increasing acidity (low pH). The
pH of the liquors is a function of the chemistry of the coal
and the mode of scrubber operation. For example, use of an
excess of lime or limestone can increase the pH, reducing the
solubility of most components.
d. Even in the absence of appreciable quantities
of fly ash, sludge liquors may contain species, such as chlorides
and certain trace metals, which can be volatilized during coal
or oil combustion and removed in the scrubber. These species
are generally not collected by dry ash collection techniques
so they are emitted to the atmosphere and consequently not found
in the ash liquor. (This indicates the potential multipollutant
control capability of wet scrubbing.)
e. Data indicate that untreated scrubber sludge
settles to 30-657o solids. At this concentration, sludge would
require more storage volume per unit weight than coal ash, which
settles to about 80% solids. Technologies such as oxidation
are being developed to increase the solids content, thereby
decreasing the volume required for storage.
6. The enacted Federal Water Pollution Control
Amendments of 1972 and the proposed solid waste management acts
require EPA to issue and periodically update guidelines and
limitations regarding water discharge and waste disposal
-6-
-------
practices. In the Federal Water Pollution Control Act Amend-
ments of 1972, Congress stated that the national goal was to
eliminate the discharge of pollutants into all waters. Fending
legislation, the Safe Drinking Water Act of 1974 strongly
addresses the need for protection of groundwater supplies.
It is apparent that the approach Congress is taking is the
elimination or minimization of discharges into surface waters
and groundwaters. Typically, lime/limestone systems are
designed to operate in a closed-loop mode, which means that
there is no direct discharge of liquor from the sys-tem. A
certain amount of liquor is contained in the system''s waste
sludge; however, proper disposal methods can prevent leaching
of this liquor to the natural water system. Therefore,
technology is available for compliance with the restrictions
set forth by this legislation. Additional research and develop-
ment is planned and underway to insure the uniform applicability
of the best available technology to the variety of F6D systems
installed or contemplated.
II. APPROACHES TO DISPOSING OF OR UTILIZING SCRUBBER
SLUDGE MATERIALS
1, Appreciable commercial utilization of sulfur
oxide sludge is unlikely. Disposal by ponding and landfill
appears to be the only important near-term alternative.
2. Based on 15 current lime/limestone FGD system
installations, utilities are presently favoring ponding over
landfill disposal techniques by about a 3:2 ratio.
-7-
-------
3. Technologically, a high degree of confidence may
be achieved with an approach incorporating pond lining in
combination with chemical treatment (fixation). It appears,
however, that this conservative approach may not be necessary
but that proper ponding or fixation alone may be environmentally
sound.
4. For ponding, available information indicates
that water pollution problems can be prevented by proper pond
engineering, installation of a pond liner, and by operating in
a closed-loop mode. Installed costs for synthetic pond liners
for a 0.4 to 4.0 hectare pond (1 to 10 acres) range from ap-
proximately $1.20 per square meter ($1.00 per square yard) for
thin synthetic membranes up to $7.90 per square meter ($6.60
per square yard) for 30 mil fabric reinforced rubber. Clay
lining starts at $1.80 per square meter ($1.50 per square yard)
and may go up to $10.80 per square meter ($9.00 per square
yard) or higher depending on the hauling distance. These cost
figures do not include pond excavation costs. Based on the
assumptions given in Case 5, Table 2 (in Technical Discussion
Summary), $1.20 per square meter ($1.00 per square yard) is
equivalent to about $4/Kw capital cost. A general cost range
for a total ponding operation, exclusive of future reclamation
costs, is $2.50-4.50 per ton of wet sludge (50% solids). Based
/
on the same assumptions referred to above, this range is equiv-
alent to 0.6-1.0 mills/Kwh. Specifications for lining materials
for sludge disposal applications and, consequently, their cost
effectiveness are not well defined. Because of nonsettling
characteristics of sludges, ponding may not be an acceptable
disposal method in many areas because it may result in land
deterioration and be a temporary solution only. On the other
hand, ponding does enable the operator to postpone determination
of final disposal for several years. Documented cases of tech-
nology and costs for effective reclamation of sludge ponds are
-8-
-------
not available. However, available data on sludge chemical
fixation (see 11(5)) indicate that this technology can eliminate
land deterioration problems.
5. For landfilling, available information indicates
that chemical treatment (fixation) of sludge will eliminate
land deterioration problems in cases where the load-bearing
characteristics of untreated sludge are inadequate. Fixation
may also avoid water pollution problems in unlined landfill
sites, but further study is needed to evaluate the degree of
leaching and the degree of attenuation offered by different
substrates for individual sludges. Fixation processes are being
commercially offered and in some cases vendors have active con-
tracts with utilities to handle lime/limestone sludge. Because
of proprietary considerations, vendors and utilities generally
have not released details of their sludge disposal processes;
therefore, it is difficult to completely assess their cost.
However, available small-scale test data have indicated lower
permeability and leachability, as well as improved compressive
strength and other material properties. Operating costs
reported by utilities performing their own disposal range from
$5.25-10/wet ton for on-site disposal; this is exclusive of
capital costs. Vendors' estimates are much lower, ranging
from $2-6/wet ton as a total disposal cost. These costs are
affected by many variables, including sludge characteristics
and chemistry, transport distances, and land values, resulting
in the wide range for the estimates. Typical cases are expected
to be in the range of $2.50-5.00/wet ton. Based on the as-
sumptions given in Case 5, Table 2 (in Technical Discussion •
Summary), fixation at $2.50-5.00/wet ton (including ash) is
equivalent to approximately 0.6-1.1 mills/Kwh.
-9-
-------
III. ALTERNATIVE SULFUR BY-PRODUCTS
1. Economic comparisons of lime/limestone F6D with
regenerable FGD systems are strongly influenced by sludge dis-
posal costs which in turn are dependent on ash content and
mode of disposal.
Where the sludge includes no ash, lime/limestone
scrubbing systems appear to have cost advantages over regener-
able FGD systems up to sludge disposal costs of about $4 per
wet ton. Lime/limestone scrubbing systems no longer appear to
be competitive with regenerable FGD systems if sludge disposal
costs are greater than about $10 per wet ton, assuming markets
are available for the by-products from the regenerable systems.
2. The only alternative regenerable FGD by-products
with significant potential markets are HzSOi* and elemental
sulfur. Elemental sulfur is the most environmentally desirable
throwaway product; it has low solubility, substantially reduced
storage requirements, and potentially can be marketed at a
later date. Technology for sulfur production has been demon-
strated in a smelter application, and the technology appears to
be transferable to steam generators. Sulfur production in an
integrated FGD unit on a utility boiler will not be demonstrated
until 1975 (EPA, Wellman-Lord FGD, Allied Chemical sulfur pro-
cess, Northern Indiana Public Service Company unit).
3. Based on lead time considerations, vendor supply,
and marketing considerations, regenerable FGD systems producing
HaSOit or elemental sulfur appear to be limited to a maximum of
about 40% of the total electric utility FGD systems projected
in 1980.
-10-
-------
IV. KEY FINDINGS RELEVANT TO TECHNICAL RECOMMENDATIONS
1. Technology is currently available which appears
to be capable of minimizing or eliminating potential environ-
mental problems associated with sludge disposal--water pollution
and land deterioration. This technology includes closed-loop
scrubber system operation, use of liner material at the disposal
site, and chemical treatment (fixation). Closed-loop operation
is currently being applied at most lime/limestone scrubber
installations. Liner materials have been in use, apparently
successfully, for many years. Although it hasn't been applied
to scrubber sludge disposal, there is no reason to believe liner
technology should not be transferable. Fixation technology is
currently offered as a commercial process. Based essentially
on small scale evaluations and limited full scale data, these
technologies appear to be effective in alleviating potential
environmental problems. Available costs for liner and fixation
technologies applied to sludge disposal cover a broad range.
2. Currently there is a wide range of lime/limestone
FGD system applications and sludge disposal approaches. Through
these activities, utilities, FGD vendors, and vendors of sludge
handling technology can be expected to identify environmental
problems and solutions, and to optimize costs of sludge disposal,
as necessary for each specific application.
3. To assure greater application and to further
minimize the environmental effects of these technologies, at
reasonable cost, additional information, primarily from large
scale sources, is needed. For untreated sludge disposal,
necessary information includes leachate effects on soil sub-
strates, liner materials, and groundwater as a function of time;
the effects of run-off or leakage on surface water; the
-11-
-------
techniques of effective sludge pond reclamation; and the
associated economics of various alternative approaches. For
fixated sludge disposal, necessary information includes perme-
ability, leachability, mechanical strength and rewatering
tendencies as a function of time for the various available
fixation processes; and the associated economics of these
processes.
4. A continuing, coordinated EPA program, with
expansion of the current program, is required to optimize- the
environmental effectiveness and to assure reasonable costs for
sludge disposal techniques over a wide range of applications.
This program will require the evaluation of utility and sludge
handling vendor efforts, as well as independent laboratory and
field evaluation of disposal processes by EPA.
-12-
-------
TECHNICAL RECOMMENDATIONS
After considering the sludge treatment/disposal
efforts currently underway by government and industry, the SOTSEP
recommends that an expanded and coordinated effort within ORD
be established with assignment of adequate responsibilities and
resources to the appropriate research, development and demon-
stration (RD&D) laboratories within the NERC's to accomplish
an integrated program plan. The Panel believes such a program
is justified on the basis that more data are necessary to assure
greater application of flue gas desulfurization and to further
minimize environmental effects, at reasonable cost.
The recommended technical program would have the
objective of optimizing the environmental effectiveness and
assuring reasonable costs for sludge disposal techniques over
a wide range of applications. The integrated program plan
^t
should contain the following essential elements:
1. Intermedia Problem Definition
This element consists primarily of chemical and
physical analyses of untreated and treated scrubber sludges and
associated liquors. It is recommended that the data base be
expanded to include sample analyses from more installations
representing a broader range of sludges indicative of typical
lime/limestone and double alkali process applications. The
expansion should include more analyses of sludge materials
from lime/Eastern coal, limestone/Eastern coal, limestone/
Western coal and double alkali/Eastern coal combinations. It
Procurement activities for implementation of substantial
portions of these elements have been initiated.
-13-
-------
would also include analysis of sludges from lime/Western coal,
carbide sludge/Eastern coal and limestone/oil.
2. Technology Survey and Small Scale Evaluation
This element consists of the following efforts:
a. Close coordination with utility and
vendor sludge treatment/disposal programs:
this includes additional survey and infor-
mation exchange visits to current and future
utility and vendor installations with active
programs regarding handling, treatment and
disposal technology, and economics.
b. Laboratory evaluation of sludges after
fixation or other stabilization treatment:
this effort includes determination of per-
meability, leachability, mechanical strength,
and other properties of sludges after treat-
ment by various vendors offering commercial
processes.
c. Field evaluation of sludge disposal with
untreated and treated (fixed) sludge: this
effort includes evaluation of an untreated
limestone/Eastern coal sludge disposal pond;
and evaluation of two simulated landfills,
one with lime/Eastern coal sludge and the
other with limestone/Eastern coal sludge,
each treated (fixated) by two different vendors
offering commercial processes. Associated
environmental monitoring and analysis of
-14-
-------
permeability, leachability, leachate/soil
interactions, groundwater effects, and mech-
anical properties would be performed for all
three sites over an approximate two to three
year period.
d. Sludge leachate/soil interaction studies:
this effort includes correlation of data from
the field evaluation above (item c) and extra-
polation to other treated and untreated
scrubber sludges with representative United
States soil.
e. Sludge leachate/liner interaction studies:
the effects of treated and untreated scrubber
sludge leachates on representative pond liner
materials would be evaluated as a function
of time.
f. Sludge leachate reuse studies: this
effort includes an evaluation of collected
sludge leachate for reuse and consideration of
an integrated approach encompassing treatment/
disposal or reuse of boiler and cooling water
blowdown and collected sludge leachate.
3. Large-scale Techno-economic Demonstrations
This element consists of cost sharing of current
and/or future large-scale utility programs to evaluate improved
handling, treatment, and disposal technology for scrubber
sludge and to generate meaningful economic data. Programs would
include appropriate environmental monitoring and applications
-15-
-------
involving untreated or treated sludges in lined or unlined
disposal sites.
4. Policy Formulation
This element involves integration of information
from all program elements and formulation of widely applicable
guidelines and recommendations for environmentally sound sludge
disposal techniques including associated costs.
-16-
-------
TECHNICAL DISCUSSION SUMMARY
The following summarizes the most important infor-
mation obtained by the SOTSEP during the course of its
activities.
I. DEFINITION OF THE PROBLEM
A. Availability of Alternative SO.. Control Technology
i^^^^^^^^^^_^^^K^M>^^^B_^MH^_*K^^^^ta^M^M«B^Ba^^H^«IIM^H^^B^^^^^^M2£l^^^^^^^^MMM^^^^^BM^^BM^»^^^«BM^^^^^^*'B
United States Department of the Interior data indicate
that net electric generation by fossil-fueled power plants will
increase from 1310 billion Kwh in 1971 to 1950 billion Kwh in 1980.
To meet this rapid increase in demand, the electric utility
industry will have to consume large additional quantities of
fossil fuels. The utilities will have to do this, however,
without violating air pollution emission restrictions on sulfur
oxides , nitrogen oxides, and particulates. Sulfur oxide restric-
tions require that the utilities make a choice from among several
alternatives. These include low-sulfur fuels, fuel cleaning and
conversion, and flue gas desulfurization (FGD).
The amount of natural gas and low-sulfur fuel oil
available to electric utilities will be supply-limited at
least until 1980. In addition, although abundant low-sulfur coal
reserves exist (primarily in the Western States), availability
in the near term will be hampered by the mining industry's
inability to expand rapidly and the high transportation costs
of delivering coal to Eastern and Mid-Western regions where the
greatest demand exists. Further, differences between Western
and Eastern coal characteristics could cause operating problems
in Eastern plants.
-17-
-------
Since low-sulfur fuel availability is inadequate,
other alternatives for meeting emission restrictions must be
considered. Technological developments in fuel cleaning,
advanced combusion, and fuel conversion areas have been rapid
in the past few years. However, since none of these schemes
has advanced past the pilot plant stage, it is unlikely that
any of these processes will have a major impact on the supply
of low-sulfur fuel in this country before 1980.
For some existing sources, relief from S0'2 emission
restrictions may be forthcoming through State action pursuant
to EPA's Clean Fuels Policy or through the use of supplementary
control systems as an interim measure until adequate constant
control measures can be applied. At this time it is uncertain
how many utility stations could burn fuel of greater than the
currently permitted sulfur content and still meet primary and
secondary national ambient air quality standards.
Estimates of economics, availability for application,
and utility applicability for alternate technologies are shown
in Table 1. It should be noted that these figures were deter-
mined as of November 1974. Many sources were used in arriving
at the costs shown. While the individual values may not be
absolute the relative costs are considered representative.
On cost, availability, and applicability bases, the most
attractive option for utilities in both near and far term appears
to be the installation of a FGD system in conjunction with burn-
ing high-sulfur (3 to 5 weight percent sulfur) coal.
For various regenerable FGD processes and lime/limestone
scrubbing systems, comparison of the total annualized costs are
provided in Figure 1. The cost of lime and limestone scrubbing
is shown as a function of sl,udge disposal costs without ash in
Figure 1. Approximate ranges of typical costs of the alternative
-18-
-------
Table 1. ECONOMIC ESTIMATES FOR 802 CONTROL ALTERNATIVES9
(1974 DOLLARS)
SOj Control
Alternative
Low Sulfur Fossil Fuels
Gas
Oil
Western Coal"
Eastern Coalb
Coal Cleaning
Physical
Chemical (Pyritic S Removal)
Desulfurization of Oil
l 1 wt 7. sulfur oil
h- '
<>O 0.3 wt 7, sulfur oil
i
Flue Gas Desulfurization Process
Double Alkali
Lime Scrubbing
Limestone Scrubbing
MgO (to H2SO&)
Wcllman- Lord (to H2SO«)
Wellman- Lord (m "?1
Cat-Ox
Fluldlzed Bed Combustion6
Coal Gasification
Low Btu gas
High Btu gas
Coal Liquefaction
Availability Applicability
For To Existing &
Application New Power Systems
Current
Current
Current
Current
Current
1978
^
Current |
Current j
1974 *]
Current
Current
Current
Current
Current
Current
1977-1978
Post 1980
Post 1980
Post 1980
Limited availability;
existing units only.
Limited low-S avail.
Limited prod.; wide
applic. to new boilers.
limited existing applic.
Limlterl low-S avail.
Limited: only ~ 25% S
removal for most coals.
Limited to pyritic coals;
full applic. to exist &
new.
(Full applicability for
oil boilers.
Wide applicability to
most existing and new
coal & oil boilers.
Applicable only for
new systems.
Generally more applicable
to new units.
Applicable to new & exist-
ing units.
Applicable to new
and existing units.
Fuel Costs
(Mills /Kvh)
4.0-6.0
18.0-20.0
4.0-6.0
4.5-9.
3.U6.
3.
15
15
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
1-6.
J
.Od
,0d
1-6.
1-6.
1-6.
1-6.
1-6.
1-6.
1-6.
1,6.
1-6.
1-6.
1-6.
0
7«
7C
7C
|
'ic
7
7
7
7
Capital Costs
N/A
N/A
N/A
N/A
$10 /Kw
$26 /Kw
N/A
N/A
$61/Kw
$45 /Kw
$50/Kw
$53 /Kw
$60 /Kw
$61 /Kw
$85/Kw
$308/K»f
$72-$109/Kw
$75-$125/Kw
$60-$90/Kw
Effective Fuel
Costs (Fuel
Annualized Cost +
Control Costs Annualized Coir-
(Mills/Kwh) trol Costs)
4.0-6.0
18.0-20
4.0-6.0
0
1
...
.8-1.5
.55
~ — ~
4.
3.
4.
18
5-9.0
9-8.2
7-8.3
.0
.0
20. 0
3
2
2
3
3
3
3
0
.55
.90
.86
.07
.67
.80
.44
.3-1.78
_._
6.
6.
6.
6.
6.
6.
6.
3.
8.
7-10.
0-9.6
0-9.6
2-9.8
8-10.
9-10.
5-10.
4-8.4
3-12.
3
4
5
1
8
12+
6.
5-9.6
8As of November 1974.
^Costs are for Western coal delivered in the West and
Eastern coal delivered in the East; additional costs
for transporting Western coal to the East (or vice
versa) are $7.50 per ton per 1000 miles.
cCoal cost Is for high sulfur (3.0-4.0Z S) Eastern coal.
Oil cost is for 3.5-4.01 S crude oil.
Pressurized fluid bed boiler combined cycle, once through system; coal.
Includes power generation equipment.
^Control considered inherent In the boiler.
-------
4.5
to
O
i
N
3
CO
o
u>
3 N
-I CO
I*. -J
to
o
u
o
UJ
N
3
Z
Z
4
4.0
3.5
3.0
2.5
-WELLMAN-LORD (STORE S)
-WELLMAN-LORD (SELL S)
WELLMAN-LORO (SELL ACID3
MAGNESIA (SELL ACID)
CAT-OX (SELL ACID)—>
.L.
2 4 6 6 10
COST OF SLUDGE DISPOSAL . WET SLUDGE WITHOUT ASH.
DOLLARS/TON
12
UNLINED
- PONDS--
(BASED ON WET FLY ASH DISPOSAL)
LINED PONDS1
Figure 1.
-CHEMICAL TREATMENT (FIXATION)- • •
^—FIXATION PLUS LINING
Process Cost Comparison for Non-Regenerable and
Regenerable Flue Gas Desulfurization Systems—
Effect of Sludge Disposal and By-Product Sales
or Discosal (Without Flv Ash"i .
-------
disposal methods are included. The ranges generally indicate
an apparent minimum representing ideal circumstances, and a
maximum based on currently available cost data. Additionally,
several by-product marketing cases for representative regen-
erable FGD systems are shown. Inspection of Figure 1 (which
includes ash disposal separate from sludge disposal) indicates
that neither throwaway nor regenerable FGD systems are clearly
preferable although lime/limestone systems have cost advantages
over regenerable systems at disposal costs up to about
$4/wet ton of sludge. Also, sale of sulfur products (as '
sulfur or as acid) is important to regenerable systems'
competitive position. Above about $7/wet ton for limestone
and $10/wet ton for lime scrubbing, these systems no longer
appear to be competitive with regenerable FGD systems, assuming
there are markets available for by-products from the regen-
erable systems.
As this figure indicates, lime/limestone FGD annual-
ized costs are strongly dependent on sludge disposal costs
which in turn are dependent on the mode of disposal; e.g.,
lined or unlined ponds, and treated sludge for landfill. For
example, for a particular lime scrubber system disposing of
sludge without ash, total annualized operating costs would be
2.8 mills/Kwh if sludge disposal costs were $1.5/wet ton of
sludge; costs would be about 3.2 mills/Kwh if disposal costs
were $5/wet ton of sludge.
Other factors which influence such cost comparisons
include local sulfur market conditions, power plant conditions
(size, age, percent S fuel, retrofit difficulty, land avail-
ability, site variables), and local regulations. Based on
current trends, technology availability, and lead time consider-
ations, lime/limestone wet scrubbing will probably comprise
the major portion (75 percent) of the total FGD systems installed
-21-
-------
by 1980. Because sludge disposal costs are an appreciable
fraction of total scrubber annualized costs, it is important
that current EPA studies of treatment/disposal costs as a func-
tion of power plants and site variables be continued.
B. Potential Demand for Lime/Limestone Scrubbing
Installation of flue gas desulfurization systems in
the utility industry is presently demand-limited and is expected
to remain demand-limited through 1975. The total generating
capacity controlled by the end of 1975 is projected''to be no more
than 10,000 Mw. Because of regulatory pressures the instal-
lation of FGD systems should become supply-limited sometime between
1975 and 1977. From 1977 to 1980 the installation of flue gas
desulfurization systems will almost certainly be supply-limited.
Based on regulatory pressures and expanding generating capacity
coupled with a clean fuels deficit, it is forecast that a maxi-
mum of over 130,000 Mw of installed coal-fired generating
capacity will need to be controlled by FGD systems by 1980.
However, the most likely demand figure by 1980 is estimated at
90,000 Mw of FGD control, or about 35% of total estimated coal-
fired generating capacity. In the post-1980 period, depending
on the commercial availability and viability of alternate clean
fuel technologies, FGD systems could be installed to the extent
they approach demand requirements. Recent projections by EPA
for the need for coal-fired utility FGD systems are shown in
Figure 2.
In the post-1975 period the projected annual rate of
application of regenerable FGD is expected to exceed that for the
non-regenerable FGD. However, based on current emphasis,
technology availability, and lead time considerations, most of
the FCD systems installed by 1980 are expected to be lime/
limestone. A minimum of 60 percent for lime/limestone has
-22-
-------
125
'o
>-
<
<
o
100
75
i
NJ
10
50
25 -J-
NOTES:
CURVES INCLUDE NEW EXISTING PLANTS REQUIRING CONTROLS
TO ACHIEVE E'THER PRIMARY STANDARDS OR NEW SOURCE
PERFORMANCE STANDARDS.
&BASED ON PESSIMISTIC PROJECTIONS FOR NEW LOW SULFUR
COAL SUPPLIES AND MINIMAL REDISTRIBUTION OF EXISTING
SUPPLIES.
bBASED ON OPT MISTIC PRO JECTIONS -'FOR LOW SULFUR COAL
SUPPLIES AND MAXIMUM REDISTRIBUTION OF EXISTi.NG SUPPLIES.
1975
1976
1979
4-
I960
4-
1981
Figure 2.
1977 1378
TIME , YEAR
Cumulative Need: F6D for Coal-Fired Power Plants.
-------
been projected, but current trends indicate this figure will
be much higher. Other applications of lime/limestone scrubbing
(e.g., oil-fired utility boilers, coal-fired industrial boilers)
could make an effective figure of 90,000 Mw for control by this
system a realistic projection.
C. Quantification of the Problem and Comparison
With Analogous Environmental Problems
The necessity to dispose of or utilize large quantities
of sulfur removed from the flue gas is inherent in any flue gas
desulfurization system. The sulfur compounds produced by flue
gas desulfurization systems fall into two general categories:
throwaway or saleable products. Lime/limestone and double alkali
scrubbing systems generate throwaway sulfur oxide sludge products
with little commercial value projected at the present time.
Limestone scrubbing processes ordinarily produce sludges con-
taining CaS03-%H20, CaSO^-2H20, and CaC03 ; lime sludges may
contain unreacted lime as well.
A power plant S0« scrubbing system can be designed with
the alternative of collecting flyash simultaneously with the flue
gas scrubbing operation or of collecting flyash upstream of the
scrubbing operation, using precipitators and/or mechanical
collectors. Additionally, the ash may be disposed of with the
scrubber sludge or independently of it. As yet, no consistent
approach has been taken by the utility industry. For coal-fired
installations where efficient particulate removal is not installed
upstream of the wet lime/limestone absorber, scrubber sludges
can contain large quantities of coal ash.
The amount of sludge generated by a given plant is a
function of the sulfur and ash content of the coal, the coal usage,
the load factor (on-stream hours per year), the mole ratio
-24-
-------
of additive to S02> the S02 removal efficiency of the scrubbing
system, and the moisture content of the sludge. Table 2 shows
the effects of variations in the assumed values of these para-
meters. The values listed in the national average represent
a mix of Western and Eastern plants expected in 1980 based on the
trends shown by present flue gas desulfurization system orders..
Assuming the projected 90,000 Mw of FGD control is
accomplished entirely by limestone installation^ using the
national average annual sludge production rates per 1000 Mw of
controlled generating capacity, the amount of wet sludge and
ash (50 percent moisture) that will have to be disposed of
annually by 1980 is predicted to be 119,000,000 metric tons/year
(131,000,000 tons/year). Depending on the viability and commercial
availability of alternate clean fuel technologies, sludge
production rates could substantially increase in the post-1980
period.
To put sulfur oxide scrubber sludge into perspective
with other wastes, two approaches were taken. The first was to
view sludge as part of the land and solid waste impacts associated
with a 1000 Mw coal-fired utility unit, thereby assessing intra-
industry effects. The second was to compare sludge with wastes
from other industries and activities.
* It is unlikely that all coal-fired utility FGD installations
will be lime/limestone systems. However, the majority are
expected to be, and other applications (e.g., oil-fired utility
boilers, coal-fired industrial boilers) could make the projected
sludge production figure quite realistic.
-25-
-------
Table 2. TYPICAL QUANTITIES OF ASH AND SLUDGE PRODUCED BY A 1000 MW COAL-FIRED GENERATING
Si Aims CONTROLLED WITH LIME/LIME STONE FLUE GAS DESULFURIZATION SYSTEMS, SHORT TONS PER YEAR
ro
Case 1 Case 2
Base Case EffecC of Stoichiometry
Coa1 Ash, dr"
Coal Ash, wet (80% solids)
Limestone Sludge, dry
CaS03-l/2H20
CaS04-2H20
CaCO-> unreacted
Tocal
Limestone Sludge, wet 1
(507, solids)
Limestone Sludge, wet 1
(with ash)
Lime Sludge, dry
CaS03-l/2H20
CaS04-2H20
CaO unreacted
Total
Line Sludge, uet
(507. solids)
Line Sludge, wet 1
(with ash)
Assumptions:
Coal: % S
% ash
Plant: hr/yr
Ib coal/Kwh
Scrubber: % SOo removal
CaO/S02 mole ratio
CaCOj/SO? mole ratio
% sulfite oxidation
338,000
423,000
322,000
48,000
185,000
333, OtiO
,110,000
,790,000
322,000
48,000
52,000
422 ,OOO
844,000
,520,000
3.5
12
6400
0.88
90
1.2
1.5
10
338,000
423,000
322,000
48,000
92,000
462 .Odd
924,000
1.600,000
322,000
48,000
17,000
387,000
774,000
1,450,000
3.5
12
6400
0.88
90
1.0
1.2
10
Case 3
Effect of SO2
Removal Efficiency
338,000
423,000
286,000
42,000
216,000
544, ood
1,090,000
1,760,000
286,000
42,000
69,000
397, ood
794,000
1,470,000
3.5
12
6400
0.88
80
1.2
1.5
10
Case 4
Effect of Coal S
282,000
354.000
64,000
10,000
37.000
111,000
222,000
786,000
64,000
10,000
11,000
85' , 000
170,000
734,000
0.7
10
6400
0.88
90
1.2
1.5
10
Case 5
19SO
National Average
338,000
423,000
261,000
39,000
92,000
392 ,000
78',, 000
1,460,000
261,000
39,000
22,000
322\oGo
644,000
1,320,000
3.0
12
6400
0.88
85
1.0
1.2
10
-------
As shown in Table 3, the annual land and solid waste
impact of a 1000 Mw coal-fired electric energy system equipped
with flue gas desulfurization (FGD) for SOV and particulate
A,
removal is 12,000 to 14,000 hectares (30,000 to 35,000 acres),
depending on the type of coal mining (deep or surface) used.
The coal mining operations appear to have the greatest impact
in terms of land use and environmental effects. Although the
right-of-way required for transmission lines actually consumes
more land than coal mining, this right-of-way land is still
available for other uses, public or private, and aside ffom
aesthetics, the environmental effects are minimal.
A plant equipped with a lime/limestone FGD system and
using ponding for disposal would require just over 2 times as
much total area as a plant site without the SOV and particulate
Ji
control system. For comparison, this same plant would require
about 1.5 times the total area of a plant with particulate
control only and ash disposal by ponding. This increase in area
(which may be at the plant site or at some remote location) is
required for the disposal of the solid wastes generated by the
FGD system.
Table 3 also shows that large quantities of wastes are
involved in coal mining and processing operations. It can be
seen that the FGD system will produce quantities of wastes about
3 times greater than for deep mines, but about half that for
strip mines.
Table 4 presents a semi-quantitative comparison of
major U.S. solid wastes on an as-disposed-of basis. In addition
to quantities of wastes, typical compositions, disposal methods,
potential environmental problems, and disposal costs are shown.
Quantities are not directly comparable since they are based on
many different sources and time periods.
-27-
-------
Table 3. COMPARATIVE LAND AND SOLID WASTE IMPACT OF 1,000 MW ELECTRIC ENERGY SYSTEM (0.75 LOAD FACTOR)
(LOW LEVELS OF ENVIRONMENTAL CONTROLS EXCEPT FOR INSTALLATION OF A LIMESTONE FGD SYSTEM FOR SOx AND PARTICULATE REMOVAL)
Land Affected,
acres"
Annual Solid
Waste Produced,
short tons
Environmental
Impact
Typical Tech-
nique^)
Available to
Minimize
Impact
Mining (Cc
9,120
97,141 (wet,
977. solids)
(101,346 with
acid drainage
sludge)
1) Potential
land degra-
dation due
to subsi-
dence ;
2) Acid mine
drainage
water pollu-
tion problems
I) No well
developed
cost-effec-
tive tech-
nology to
control sub-
sidence;
2) Neutraliz-
ation of mine
drainage with
lime
al)
14,010
2,762,000
(wet, 98%
solids)
(2,762,328
with acid
drainage
sludge)
1) Mined
land made
barren pre-
cluding
wildlife
habitat, re-
creation and
most other
uses; 2) Acid
mine drainage
water pollu-
tion problems
1) Intensive
land recla-
mation can
restore most
strip-mined
land; 2) neu-
tralization
of mine
drainage with
lime
161
454,092 (wet,
99% solids)
1) Culm piles;
2) Water pollu-
tion: a) acid
drainage;
b) siltation;
3) Air pollu-
tion: a) dis-
charges S02, CO
& HjS; b) poten-
tial spontan-
eous combustion
Compacting In
holes, mines,
quarries, etc.
Transport
2,213
0
Use of
land for
railroad
beds
N/A
Conversion
(Plant Site)
350
0
Use of land
for power
plant site
N/A
System,
Untreated
Ponded Sludge3
367
(30 ft lepth)
1.460,000 (wet,
507. solids)
1) Potential
groundwater
pollution
problems;
2) Land poten-
tially made
useless if
s ludge not
treated or
permanently
dewatered
1) Although
reclamation is
feasible, no
well developed.
cost-effective
technology has
Transmission
17,188
0
Use of land
for trans-
mission line
right of way
N/A
Tot a
Deep
29,399
2.011.233
N/A
N/A
Is
Surface
34,289
4.676.092
N/A
N/A
been demonstrated;
2) Sound pond management, use of Impermeable pond
liner, and operation of FGD system in closed- loop
mode can minimize water pollution. (As an
alternative to ponding, chemical fixation and land-
fill appears to have potential for solving both water
pollution and land reclamation problems.)
CO
? See Table 2, Case 5, for assumptions (also Includes ash).
D Land affected Is expressed as a time average of the amount of land In use over 30 years.
variable use (waste storage) is 15 times the annual Incremental damage.
Fixed land is taken at Its full amount; average
-------
Table 4. COMPARISON OF MAJOR SOLID WASTE DISPOSAL PROBLEMS8
Waste Material
Municipal and
Industrial
Refuse6
Culm Pllesc
Mineral Ore
Wastes'1
Coal Ash
Limestone
Scrubber
Sludge
(excluding
coal ash)
Quantity Disposed
Annually In Referenced Year
(metric tons, as disposed of)
360,000,000 (1973)
(75% solids)
>91,000,000 (1969)
(dry basis)
1,300,000,000 (1970)
(dry basis)
95.000.000e (1980)
(80% solids)
64,000,OCOf (1980)
(50% solids)
(119.000.000 Including ash)
Composition
40% municipal refuse,
60% Industrial refuse
Typical Composition;
paper waste (44%); food
waste 08%) ; glass and
ceramic wastes (9%) ;
garden waste (8%); rocks,
dirt, etc. (4%); plastics,
rubber, leather, textile,
wood wastes (8%).
Waste coal, slate,
carbonaceous &
pyritlc shales, clay,
trace metals
Rock waste from mining
operations
Solids Composition (wt.%)
S102 (30-50) , AlnOi
(20-30), Fe203 (10-30),
CaO (1.5-4.7)7 K,0 (1-3),
MgO (0.5-1.1). Na20 (0.4-
1.5), T102 (0.4-1.3),
S03 (0.2-3.2), C (0.1-4. OX
B (0.1-0.6), P (0.01-0.3),
and trace metals
Solids - generally mix-
tures of CaS03>%H20,
CaS04-2H20, and CaC03
Liquor - contains various
amounts of dissolved
species which originate
in the coal, alkali, and
makeup water
Method of
Disposal
Landfills,
incinera-
tion
Surface
piles,
landfills
Surface
piles,
landfills
Ponding,
landfills
Ponding,
landfills
Land Use or
Reclamation
Cons iderat ions
Cover material
needed to
support vege-
tation
Cover material
required for
plant growth.
Provision for
collection of
drainage
Needs cover
material
Needs cover
material
Untreated
'sludge
difficult to
dewater
Environmental
Problems
wich Minimal
Pollution Control
Undefined ground-
water & surface
water pollution;
potential air
pollution
(Incinerator
emnlssions, odor)
Undefined water
pollution; sil-
tation; acid
drainage; pos-
sible air pollu-
tion (odor);
spontaneous
combustion
Undefined ground-
water & surface
water pollution
Undefined ground-
water and
surface water
pollution
Potential ground-
water & surface
water pollution
Estimated
Disposal
Costs (S/ton)
1-4 (landfill)
5-12 (inclnera
tion)
0.30-0.50
<0.50
0.50-3.00
(exclusive
of pond
construction
costs)
2.50-4.50/wet
ton (ponding)
2- 10 /wet ton
(fixation and
landfill)
1
ro
-------
Table 4 (Concinued). COMPARISON OF MAJOR SOLID WASTE DISPOSAL PROBLEMS3
Waste Material
Municipal
Sewage Sludge
Phosp'-.iica
Rock Slime8
-C-._ ;.i.-.C
Zrain-.-e
Sludge"
Gypsu- From
Fertilizer
Manufacture^
Quantity Disposed
Annually in Referenced Year
(metric tons, as disposed of)
55,000,000 (1980)
(0.1-20% solids)
760,000,000 (1970)
(4-6% solids)
i, 207, 060 (1973)
(l-5ci solids)
28,000,000 (1973)
(85-90% solids)
Composition
Composition of Raw
Primary Sludge, %:
Volatile matter - 60-80
Ash - 20-40
Insoluble ash - 17-35
Greases 6c fats - 7-35
Protein - 22-28
NH$N03 - 1-3.5
P205 - 1-1.5
Cellulose - 10-13
Trace metals
Solids Composition (wt.%)
PiOs (9-17) , A1703 (6-
18), SiO, (31-46), CaO
(lA-23)/Fe203 (3-7),
MgO (1-2), C02 (0-n,
F (0-1), BPL (19-37),
LOI (9-16), trace
metals
Typical Solids
Composition (wt.7.)
caso4 iwy, Mgo ii),
MgSOA (5), Fe203 (15),
CaO 73), Mn,03 T4) ,
S3.07 (20), Al,03 (12),
trace metals
Chiefly CaS04.2H20
Method of
Disposal
Ponding,
landfills
Ponding
Ponding
Ponding,
surface
piles
Land Use or
Reclamation
Considerations
Hard to dewater,
difficult to
develop
Hard to dewater
(settles to
only 30% solids
after years) . Not
established that
dried solids will
support vegeta-
tive growth.
Hard to dewater
Needs cover
material to
support vegeta-
tion & make
aesthetically
acceptable
Environmental
Problems
with Minimal
Pollution Control
Undefined ground-
water & surface
water pollution;
potential air
pollution
Undefined ground-
water & surface
water pollution
Undefined ground-
water & surface
water pollution
Undefined ground-
water & surface
water pollution
Estimated
Disposal
Costs ($/ton)
0.50-10
0.03-0.05
0.04-0.25
I
10
o
-------
Table 4 (Continued). COMPARISON OF MAJOR SOLID WASTE DISPOSAL PROBLEMS8
Waste Material
Taconite
Tailings
Quantity Disposed
Annually in Referenced Year
(metric tons, as disposed of)
1.100. 000. OOO1 (1971)
(4-5% solids)
Composition
Typical Solids
Compos it ion (X) :
Fe 15
SI 33
Al 0.35
Ca 1.67
Mg 2.55
Mn - 0.37
Ti - 0.030
P - 0.026
Na - 0.20
K - 0.08
S - 0.03
C - 0.11
H - 0.10
0 - 46.40
Method of
Disposal
Ponding,
lake dump-
ing
(Reserve
Mining Co.)
Land Use or
Reclamation
Considerations
Fertilization,
mulching, etc.
required for
reclamation of
ponds
Environmental
Problems
with Minimal
Pollution Control
Potential ground
and surface
water pollution
Estimated
Disposal
Costs ($/ton)
0.005-0.05
(lake
dumping)
(a)
(b)
(c)
(d)
fl!
For references, see Volume II. Table 1-10.
Exclusive of agricultural and mining wastes.
Bituminous coal only.
(d) Mining wastes from metal and non-metallic ores, exclusive of fossil fuels: »» piui-eo
Assumptions: 12% ash, 6400 hr/yr, 248.000 Mw Installed coal-fired generating capacl., „ ,, _«,
Assumptions: 3% S, 12% ash, 6400 hr/yr, 90,000 Mw controlled generating capacity, 85% S02 removal, 0.4 kg coal/Kwh, 1.2 CaC03/S02
(inlet) mole ratio, 10% oxidation
(g) 80% disposed of in Florida.
(h) Most acid mine drainage comes from abandoned mines and receives no treatment.
(i) Assumptions: >100 million tons crude taconlte ore annually, 25% average iron content.
no processing wastes included. . .
'— - — -slty U980), 0.4 kg coal/Kwh.
601 beneficiation.
-------
Comparison of quantities of solid waste generated
by various industries provides a means of placing projected
figures for scrubber sludge production into perspective. Two
bases of comparison can be made: quantification on a wet basis
(or as disposed of) represents the magnitude of waste actually
handled by the industry, while a dry basis serves as a more
uniform basis of comparison. Both techniques indicate that
waste disposal problems similar in magnitude to that posed by
scrubber sludge are dealt with by several industries.
Considering the quantities of wastes disposed of on a
wet or as-disposed-of basis, of those wastes surveyed in Table 4
several are generated in significantly greater amounts than
projected 1980 scrubber sludge. Both mineral ore wastes and taconite
tailings production rates are approximately an order of magni-
tude greater than the projected sludge production rate, while
phosphate slimes, municipal/industrial refuse, coal ash from
coal-fired utilitiesj and culm pile material also greatly
exceed sludge in amounts generated. Total projected sewage sludge,
gypsum from phosphate fertilizer manufacture, and acid mine
drainage sludge production quantities are less than that of
projected scrubber sludge.
As is the case for scrubber sludge, ponding and land-
filling provide the major mechanisms of disposal for most waste
products. In terms of land use and reclamation, and potential
surface water and groundwater pollution, these disposal mechanisms
have many points of similarity for the various industries. In
some cases, land use for waste disposal has destroyed wildlife
habitat and is aesthetically objectionable. In addition, all
wastes have the potential for varying degrees of surface and
groundwater pollution depending on their chemical compositions
and solubilities, and the location, design, and operation of the
-32-
-------
disposal site. With proper site selection and design (possibly
including a permanent impermeable liner) and sound operating
practices, however, surface water and groundwater pollution can
be avoided.
To reclaim the disposal site, most of the stable wastes
require only a cover material to support growth of vegetation
and to prevent eventual erosion of the wastes by run-off water.
However, some wastes (phosphate rock slime, sewage sludge,
untreated scrubber sludges) are very resistant to dewatering
and could reslurry in the pond or landfill. In some cases,
these disposal sites could become only temporary storage sites
which could present deferred disposal problems as well as
difficult land reclamation problems. Fixation technology, now
commercially available and applied at several full-scale instal-
lations, appears to be a successful approach to land reclamation.
In Florida, reclamation of slime ponds has been successfully
achieved using tailings from the flotation process to aid in
dewatering. Another type of approach to the potential.land use
problem is based on production of a sludge more amenable to
landfill disposal by an oxidation process.
Costs for waste disposal vary greatly depending on the
treatment and transportation of the wastes. Disposal costs are
minimal for^1 phosphate rock slime and similar wastes which typically
are not treated, are disposed of near the plant site, and have
little land reclamation activity. The projected cost range for
disposal of scrubber sludge is broad. The low end represents no
treatment and onsite disposal in an unlined pond. The high
end represents steps to solve both the land reclamation and water
pollution problems by chemical treatment and transportation to an
off-site landfill. Discharge of scrubber sludge to a lined pond
solves the water pollution problem only and, based on available data,
typical costs would be in the range of $2.50-4.50/wet ton.
-33-
-------
In summary, based on preliminary comparisons of
available information on quantities, compositions, and current
disposal methods, untreated scrubber sludge disposal may
produce an environmental impact somewhat analogous to those
associated with other solid wastes such as culm piles, municipal
sewage, municipal and industrial refuse, and coal ash. Signi-
ficant quantities of scrubber sludge are projected for 1980,
but waste disposal problems of similar and larger magnitudes have
been dealt with by industry for many years. Although the total
environmental impact associated with disposal of untreated scrubber
sludge in a soil-lined disposal area is not well-defined,
currently available technology has the potential for environ-
mentally acceptable disposal. Furthermore, solutions to achieve
satisfactory disposal will be influenced by emerging environ-
mental restrictions. Research efforts to thoroughly evaluate
potential hazards and available technology is continuing through
government-funded contractors, utilities, and fixation tech-
nology vendors.
D. Relationship Between Sulfur Oxide Scrubber
Sludge. Standards/Regulations, and Enforcement
In promulgating New Source Performance Standards for
steam generators and guidelines for State implementation plans,
the effects of flue gas desulfurization systems were considered,
including the generation of sludges. However, in 1971 when these
actions were taken, there had been little experience in processing
the relatively small quantities of sludges that were being
generated. EPA had considered the problem; no deleterious
effects were traced to sludge disposal, but the potential for
groundwater and surface water contamination was recognized. It
was judged that the sludge was similar to other wastes that were
being generated by U.S. industries and could be handled using
-34-
-------
techniques that were known, even if they hadn't been applied to
full-scale installations.
In the past 2 years,the electric utility industry has
indicated dissatisfaction with SO2 restrictions in general and
the applicability of flue gas desulfurization systems in par-
ticular. At the October-November 1973, EPA enforcement hearings
on power plant pollution control, several utilities cited
adverse environmental effects of sludge disposal and costs as
principal obstacles to the installation of flue gas' desulfuriza-
tion systems. Legal challenges from utilities have primarily
questioned the adequacy of scrubbing technology, particularly
system reliability, and the necessity for sulfur oxide control.
However, sludge disposal aspects have been cited and, specifically,
environmental impact statements documenting EPA consideration of
associated environmental problems have been an issue.
The impact of the enacted Federal Water Pollution Control
Amendments (FWPCA) of 1972 and the proposed Solid Waste Manage-
ment Acts on scrubber sludge disposal cannot be fully evaluated
at this time. However, implementation of both acts requires
EPA to issue guidelines and limitations regarding water discharge
and waste disposal. These guidelines will be issued and peri-
odically updated on the basis of best available control tech-
nology. In the Federal Water Pollution Control Act Amendments
of 1972 Congress stated that the national goal was to eliminate
the discharge of pollutants into all waters. The act appears
to encompass any pollutant discharge with the potential for
degrading water quality directly through seepage, discharge, or
run-off, or indirectly through groundwater contamination.The
Safe Drinking Water Act of 1974 strongly addresses the need for
protection of groundwater supplies. It is apparent that the approach
Congress is taking is the elimination or minimization of
-35-
-------
discharges into surface waters and ground waters. In view of .
legislative restrictions it appears that it will be necessary to
prevent or control leaching to the ground or surface waters.
Typically, lime/limestone systems are designed to operate in a
closed-loop mode, which means that there is no direct discharge
of liquor from the system. A certain amount of liquor is contained
in the system's waste sludge; however, proper disposal methods'
can prevent leaching of this liquor to the natural water system.
Additional information concerning the chemical and physical
characteristics of the wide variety of FGD systems and associated
scrubber liquors and sludges will insure responsible- implementa-
tion of legislation. Programs which are planned and underway
will provide this necessary information.
E. Nature of the Material
A limited amount of data is available on the chemical
nature of various scrubber sludge materials; these data can be
used to help quantify potential environmental effects of sludge
disposal. Sludges from different units exhibit a wide varia-
tion in chemical properties, but are generally mixtures of
CaS03.%H20, CaS0^.2H20 (gypsum), CaCO.j (limestone), and fly ash
in varying proportions.
No definite industry trends have been observed regarding
ash collection and disposal, separately or in conjunction with
SC>2 scrubbing and sludge disposal. At this time, there is
insufficient information on which to base these decisions.
However, since fly ash disposal has been practiced by utilities
for many years, fly ash characteristics provide a reference
point for comparison with sludges. Some qualitative comparisons
of ash and scrubber sludge are presented below:
-36-
-------
1. The solid phase of scrubber sludge will
consist essentially of the calcium compounds
noted above. These calcium compounds have a
limited solubility in sludge liquors. The
major components in fly ash are even less
soluble.
2. Scrubber sludge and ash solids will con-
tain trace elements originating in the coal.
Based on data available at this time,' the major
source of heavy metal concentrations in sludge
is the coal. Trace elements and other species
may also originate in the limestone or lime,
the make-up water, and ash sluice water, but
their contribution to the total trace element
content of the sludge is minor.
3. Sludge and ash liquors will contain dis-
solved species from the solid constituents in
accordance with solubilities which are gen-
erally an inverse function of pH. The chem-
istry of the coal, particularly chlorine and
sulfur content, and the type of scrubber
system employed will determine the pH of the
untreated sludge liquors.
4. Liquors associated with-scrubber sludge
may also contain species such as chlorides
and certain trace metals which are volatilized
during coal combustion and removed in the
scrubber. These species are generally unaffected
by dry ash collection techniques so they are
emitted to the atmosphere and not found in the
ash liquor. This indicates the multi-pollutant
control potential of FGD systems.
-37-
-------
5. Limited data indicate total dissolved
solids (TDS) vary widely in sludge liquors and
ash liquors. Levels for scrubber sludge liquors
tend to be considerably higher, in some cases
by an order of magnitude or more. These higher
TDS values include calcium compounds, mag-
nesium compounds, trace elements and chlorides.
In summary, a qualitative comparison of soluble species
found in sludge liquors with those found in ash liquors indicates
that sludge liquors would contain greater concentrations of total
dissolved solids and levels of major species (e.g., sulfate,
chloride, carbonate, calcium and magnesium). Relative levels of
trace elements will depend, however, on the chemistry of the
coal burned and the type of scrubbing system employed. Limited
preliminary data on chemical analysis of sludge liquors, compared
to drinking water standards (a stringent basis for comparison),
indicate that some sludges may have excessive amounts of one or
more of the following: manganese, lead, copper, cadmium, selenium,
boron, nickel, magnesium, chloride, sulfate, and total dissolved
solids. Some of these and other liquid-phase soluble species are
potentially harmful, and would result in potential water pollution
problems if they entered surface or groundwater in sufficient
concentrations.
Many variables (coal, limestone, make-up water, opera-
ting parameters) can influence the quantities of the soluble
species. More information is needed to quantify the variable
effects, and to better define the chemical characteristics of
sludge from large continuously operating systems .
-38-
-------
There is wide variation in physical properties for
sludges from different units. These properties are influenced
by many system variables including the percentage of fly ash and
the calcium sulfite/sulfate ratio. The physical properties
strongly influence the ease with which the material can be
handled and transported, and type and degree of the land
reclamation problems for abandoned sludge disposal sites. The
main problem relating to physical properties of sludge is
difficulty in dewatering. In addition, the results of some
preliminary studies indicated a tendency for sludge to rewater
to its original water content.
Test data show that the sludges are thixotropic in
nature and have retarded settling characteristics. The
influence of ash content on settled density of sludge is not well
understood. This information could bear upon a decision regarding
separate or combined disposal of ash and sludge. Normal pond
settling with untreated material will probably result in a
final settled density of less than 50% solids. At 50% solids,
sludges have low bearing capacity and compressive strength.
Preliminary results from bench-scale studies indicate that
untreated sludges show a tendency to rewater after being sub-
jected to a dewatering operation (e.g. , drying) then exposed to
water (rainfall). This characteristic would tend to thwart
attempts to increase the final settled density by employing a
dewatering unit operation alone.
-39-
-------
II. APPROACHES TO DISPOSING OF OR UTILIZING
SCRUBBER SLUDGE MATERIALS
A. Commercial Utilization
Investigations of the potential commercial utilization
of power plant desulfurization sludges have been made by numerous
government and private organizations. These organizations include
Federal agencies; research centers; universities; commercial
research, processing and sales corporations; national trade
associations, and private researchers. The results of their
efforts have been disseminated through symposiums, technical
reports, newspapers, and periodicals. A review of these refer-
ences indicates that the consensus of those most knowledgeable
about the potential utilization of desulfurization sludges is
that, although some commercial usage is feasible from a technical
and economic standpoint, the potential outlet is so small that
the vast majority of the sludges will not be marketed.
Attempts have been made to develop technology to apply
sludges to the existing ash product market or to develop new
applications in which the sludge might be used. Such develop-
ments and investigations have been reported by research centers
including West Virginia University's Coal Research Bureau,
Combustion Engineering, and IU Conversion Systems, Inc. These
developments include mineral wool, bricks, sintered concrete
products, soil amendment, sulfur recovery, gypsum, mineral recovery,
road base materials, parking lot materials, artificial aggregate,
lightweight aggregate, and aerated concrete.
-40-
-------
It was eve'ntually recognized that, despite the many
potential fly ash products with quality equal to or superior to
existing materials, the use of fly ash was extremely limited;
it was also recognized that the situation would be even worse
for sludge. Major inhibitions to the use of sludge include highly
variable chemical and physical properties, high transportation.
costs, requirement for dewatering for many applications, and
inability to economically compete with other materials.
It is therefore concluded that, at least through 1980,
disposal should be the major consideration for the handling of
throwaway sludges on a nationwide basis.
B. Present and Planned Utility Industry Disposal
Programs
The major options for sludge disposal are ponding and
landfill. Table 5 summarizes dewatering techniques and ultimate
disposal modes for 15 lime and limestone FGD systems at utility
sites; it can be observed that utilities are selecting ponding
over landfill as an ultimate disposal mode by a ratio of about
3:2. For those sites selecting the landfill mode, dewatering
techniques (such as filtering or centifuging) and/or sludge
fixation processes have been or will be used to attempt to
produce an acceptable landfill material.
The wide variety of approaches indicated may be based
on factors such as: non-uniformity of local regulations; disposal
site location and ownership; disposal site proximity to ground
or surface waters; soil permeability; variations in chemical
and physical properties of sludge; variations in scrubber
processes and types of ash collection and disposal.
-41-
-------
Table 5.
SL'JOGE TREATMENT/DISPOSAL TECHNIQUES FOR SELECTED UTILITY LIME/LIMESTONE FGD SYSTEMS
(C = Current; P = Possible Additions)
Final Disposition
Facility
(Availability
Status)
TVA-Shawnee
(Current)
Sorbent
Fuel
Limestone
& lime
Eastern
coal
Scale
Proto-
type
Clari-
fier
Dewatering Technique
Filter
Centri-
fuge
Dryer
Pond
Ponding
(Unlined)
Landfill
City of Key
West-Stock
Island
(Current)
Limestone
(coral marl)
Full
Residual
oil
(Unfixed)
Commonwealth
Edison Co.-Will
Coun ty
(Current)
Limestone
Eastern
coal
Full
(Clay
lined,
well
points)
C
(Fixed)
NO
I
Southern
California
Edison-Mohave
Lime: Current
Limestone: Oct
1974
Limestone
& lime
Full
Western
coal
C
(Fixed)
Kansas City
Power & Light-
Hawthorn
(Current)
Boiler
injected
limestone
Full
Coal
(possible E&W
blend)
C
(Well
points)
C
(Unlined)
Kansas Power &
Light -
Lawrence
(Current)
Boiler
injected
limestone
Full
Eastern
coal
C
(Unlined)
Louisville Gas
& Electric
Paddy's Run
(Current)
Carbide
sludge
(Ca(OH)2)
Full
Eastern
coal
-------
Table 5 (Continued) . SLUDGE TREATMENT/DISPOSAL TECHNIQUES FOR SELECTED UTILITY LIME/LIMESTONE FGD SYSTEMS
(C° Current; F = Possible Additions)
Facility
(Availability
Status)
Northern States
Power - Black
[Dog (Current)
Sorbent
Western
coal
Scale
Pilot
Clari-
fier
Dewatering Technique
Filter
Centri-
fuge
Dryer Pond
Final Disposition
Ponding
(Unlined)
Landfill
Kansas City Power
& Light - LaCygne
(Current)
Limes tone
Full
Eastern
coal
(Unlined)
Arizona Public
Service -
Cholla
i'Current)
Limestone
Full
Was tern
coal
(Unlined)
(Solar
evap)
puquesne Light
Phillips
(Current)
Lime
Eastern
coal
Full
C
(Curing)
(Unlined)
C
(Fixed)
Detroit
Edison -
St. Clair
(Jan. 1975)
Limestone
'Full
Eastern
coal
(Unfixed)
TVA - Widows
Creek (1976)
Limestone
Eastern
coal
Full
(Unlined)
Ohio Edison -
Bruce
Mansfield
(1975/1976)
Lime
Eastern
coal
Full
C
(Fixed)
Northern States
Power -
Sherburne
(1976/1977)
Limes tone
fly ash
Western
coal
Full
(Clay lined)
-------
Several utilities are evaluating the environmental
acceptability of their approaches to sludge treatment/
disposal. However, specific details of the monitoring.programs
are not publicly available. For example, of the utilities
listed in Table 5, three appear to be monitoring or planning
to monitor their treatment/disposal approaches.
Commonwealth Edison (Will County) - Treated
sludge material will be stored in clay-lined b'as ins
with groundwater wells. The material will cure for
approximately one month and will be inspected by
local authorities to obtain permission for offsite
disposal. The criteria for permission are unknown at
this time. Data are not currently available. Adequate
determination of the technical quality of the fixed
material and attendant costs is not expected for at
least one year.
Kansas City Power & Light (Hawthorn) - Fourteen
well points are placed around the unlined on-site
pond and are sampled periodically. No definite
data are available but it is believed that results
to date are inconclusive because the general area
may be heavily contaminated by the absorption of
leachates from fly ash ponds on the plant site.
Duquesne Light Company (Phillips) - After curing for
about 30 days in lined basins, the treated sludge will
be dredged out and hauled to a disposal demonstration
site about one mile away. The site will include one
unlined pond and two ponds lined with Hypalon. Each
pond will have underdrainage and overdrainage piping
-44-
-------
provisions to collect water for testing. Specific
analyses to be performed are not currently known.
Results of the field tests are not expected to be
available for at least one year.
Neither the utilities nor the sludge conditioning
processors are expected to readily identify all environmental
problems, solutions, or economics associated with sludge disposal.
In all likelihood, detailed information will be especially
difficult to obtain from those utilities with a sludge disposal
problem, because of concern for regulatory pressures. An EPA
program for testing and evaluation of sludge treatment/disposal
techniques is necessary to upgrade the environmental effective-
ness and cost-effectiveness of these techniques and to correlate
information with that obtained from utilities or sludge
conditioning processors.
C. Disposal by Ponding
Disposal of wastes by ponding historically has been a
favored technique in a number of industries; e.g., gypsum sludge
from fertilizer plants, phosphate slime from phosphate mining,and
ash from coal boilers.
The mechanics of pond construction and operation are
well known. However, many current pond operating techniques
were established with less regard for environmental effects than
is now considered appropriate (although they are not representa-
tive of the best available control technology). There are two
major environmental aspects associated with ponding of sulfur
oxide sludges which require consideration:
1. The water pollution potential associated with
soluble species in the sludge liquor and solid phases
2. The land deterioration associated with non-
settling sludges.
-45-
-------
Ponding of SO scrubber sludges will require particular
2i
attention to proper design and operating practice because of the
potential for groundwater pollution. However, leaching of con-
taminants to an aquifer from a pond can be avoided through proper
site selection (considering topography, geology, soil permeability,
distance to water table, etc.) and a permanent pond lining. Over-
flow of pond liquor into surface water can and should be avoided.
This will require proper pond design or total recycle of pond
liquor, with treatment of any blowdown (purge) streams. The
construction and lining of ponds is established technology.
Costs for these water pollution controls are based on
estimates for installed pond linings, exclusive of excavation.
Installation of a clay lining may vary from $1.80 per square meter
($1.50 per square yard) or higher, depending on the hauling
distance. Synthetic liners also vary widely in cost. For small
ponds, 0.4 to 4.0 hectares (1 to 10 acres), thin synthetic
membranes cost approximately $1.20 per square meter ($1.00 per
square yard) while 30 mil fabric reinforced rubber is priced
at $7.90 per square meter ($6.60 per square yard). Cost savings
can be realized for larger ponds. Based on the assumption given
in Case 5, Table 2, $1.20 per square meter ($1.00 per square
yard) is equivalent to about $4/Kw capital cost. A general cost
range for a total ponding operation, exclusive of future reclama-
tion costs, is $2.50-4.50 per ton of wet sludge (50% solids).
Based on the same assumptions referred to above, this range is
equivalent to 0.6-1-0 mills/Kwh.
The requirements of liner materials for sludge or ash
disposal applications and consequently their cost-effectiveness
are not well defined. For example, before the long term effects
of sludge or clay as a liner for sludge can be determined with
confidence, more information must be developed. As indicated
-46-
-------
in Section II.B., several sludge disposal applications of clay
linings and one Hypalon application are known.
A potential problem would be the eventual reclamation
of the pond site due to resistance to dewatering exhibited by
unstabilized sludges. This problem would be particularly diffi-
cult to solve in those areas with high annual rainfall and low
annual evaporation. Oxidation of the sulfite-laden sludges
is currently under development as one approach to enhance
dewatering. Another approach is based on treating (fixing) the
sludges prior to final disposition to produce a dewatered, solid,
load-bearing material. Such a treatment step would result in
the pond being used as a landfill site. Pond reclamation schemes
such as covering an abandoned site with soil may be possible,
although the technology, effectiveness, and costs of reclamation
of sludge ponds have not been well defined.
D. Disposal by Landfill
Landfill techniques involve the disposal of sludge
treated via dewatering and/or fixation techniques. This tech-
nology aims to produce a material with physical and'chemical
properties which enable environmentally acceptable disposal as
landfill without excessive costs. A dewatering step is necessary
since slurries from the scrubber circuit are ordinarily only
5-15 percent solids by weight and must be dewatered either for
direct landfilling or preparatory to a fixation treatment
process followed by landfilling. Varying degrees of pilot plant,
prototype, and commercial experience have been obtained on
thickeners, vacuum filters, and centrifuges. They have indicated
varying degrees of effectiveness in dewatering capabilities.
Generally, due to the poor free-settling properties of sulfur
oxide sludges, thickeners are limited to dewatering to a maximum
-47-
-------
of about 45-50 percent solids, although 65 percent solids was
in one case. At this solids density, the sludges behave as a
thixotropic liquid. Vacuum filters and centrifuges have been
effective in dewatering scrubber sludges to a solids content of
up to 55-65 percent by weight. At this solids density, physical
properties of the sludge approach those of a solid. Although
pressure filters are being evaluated with municipal sewage sludge,
their applicability to scrubber sludge has not been assessed.
Further data will be necessary before it can be concluded
that a vacuum filter, a centrifuge, or possibly a pressure filter
is the most favorable dewatering equipment for sulfur oxide
sludges.
Chemical fixation of scrubber sludge and related materials
is currently being offered by several commercial groups including
the Dravo, IU Conversion Systems (IUCS), and Chemfix Corporations.
At least two of the organizations cited offer processes which
stabilize and solidify sludges via pozzolanic and other cement -
itious reactions between sludge/fly ash mixtures and small quan-
tities of a lime-type additive. Laboratory data indicate that
stabilized sludges have greatly improved mechanical properties,
diminished rewatering tendencies, and substantially lower
permeability and leachability compared to untreated materials.
Operating cost estimates for sludge fixation and
disposal vary widely. Operating costs for utilities performing
their own disposal are about $5.25-10.00 per wet ton for on-
site disposal, exclusive of capital costs. Vendors' estimates
are much lower, ranging from $2- 6 per wet ton as a total dis-
posal cost. IUCS and Chemfix estimates for complete costs,
including capital investment and local transportation costs,
are $4-5 per wet ton (507. solids). IUCS quotes a cost of
$1.50-2.50 per wet ton for an on-site disposal operation;
-48-
-------
this figure is exclusive of land acquisition costs. A Dravo
spokesman gave a disposal cost for a situation involving pump-
ing up to ten miles, exclusive of pond construction costs, of
$1-3 per wet ton (35-407, solids). A specific case involving
considerable land development and an 8-mile pumping distance
is estimated to cost less than $5 per wet ton. Typical
cases are expected to be in the range of $2.50-5.00/wet ton.
The cost of $2.50/wet ton applied to Case 5 of Table 2 (lime-
stone sludge including ash) results in an operating cost of about
0.6 mills/Kwh.
Due to the importance of sludge fixation processes and
their potential for minimizing all potential environmental prob-
lems associated with sludge, it is considered essential to
evaluate the following attributes of treated sludges as a function
of time: leachability, permeability, mechanical strength, and
rewatering tendencies. Also required are detailed capital and
operating costs over a range of applications.
E. Other Disposal Methods
Other disposal options are available for sulfur oxide
sludges, although they are not under investigation to nearly the
same extent as ponding and landfill and may have water pollution
potential. One of these is deep mine disposal whereby untreated
or treated sludge is returned to the mines) possibly in "empty cars,
However, the feasibility of this approach could be significantly
influenced by transportation costs from power plant sites. Another
sludge disposal method that has been proposed, deep well injection,
involves disposal by deep well injection into permeable subter-
ranean formations. EPA policy is to review this alternative on a
case by case basis but considers deep well injection only as a
last resort. No data are reported on this technique for sulfur
oxide sludges; however, the high solids content of these materials
-49-
-------
might cause rapid plugging of the subsurface strata, resulting
in continually decreasing injection rates.
F. Current EPA R&D Programs
The most relevant government sponsored program relating
to sulfur oxide sludges is the NERC-RTP program with The Aero-
space Corporation (El Segundo, California) entitled "Study of
Disposal of By-Products From Non-Regenerable Flue Gas Desulfuri-
zation Systems." This program.which will evaluate the technology
of sludge disposal, was formalized during late 1972 and has the
following major elements:
1. An inventory of sludge constituents in both
the solid and liquid phases. Sludges produced
from the following sorbent/fuel combinations
are being studied: limestone/Eastern and Western
coals, lime/Eastern coal, and double alkali/
Eastern coal.
2. An evaluation of the potential water pollution
and solid waste problems including consideration
of existing or proposed water effluent, water
quality, and solid waste standards or guidelines.
3. An evaluation of treatment/disposal tech-
niques with emphasis on ponding and treated and
untreated landfills. In particular, sludges
treated by two or more commercially offered processes
will be evaluated in the laboratory for mechanical
properties, permeability, leachability, etc.
4. A recommendation of the best available tech-
\
nology for sludge treatment/disposal based on the
elements delineated above.
-50-
-------
The current Aerospace contract is limited to the samp-
ling and analysis of sludges from only four power plant FGD
systems. Because of the diversity of coal types and FGD systems,
this was felt to be too small a data base upon which to draw the
general conclusions needed to achieve the program objectives.
In addition, results of the current program identified the need
for (1) a more detailed examination of possible scrubber system
alternatives for reducing the availability of soluble chemical
species to the environment, (2) greater emphasis on the cost of
sludge transport for disposal, and (3) a field study of disposal
of both treated and untreated FGD system sludges. Therefore, a
contract modification is currently being negotiated, the purpose
of which is to accomplish the following:
1. Expand the sampling and analysis effort from
four plants to eight, which will make the program
results applicable to a broader range of power plant
flue gas scrubbing applications.
2. Determine, through analytical and laboratory
solubility studies, those chemical constituents
which can be controlled by scrubber chemistry.
Examine the possible effect of the results of the
solubility studies on cost and technical adequacy
of alternative sludge disposal methods.
3. Expand disposal cost analyses to include more
detailed investigations of various transport modes;
e.g., trucking, pumping, and barging.
4. Support an EPA field study of FGD sludge disposal
at TVA's Shawnee Steam Plant, which will include test
planning program coordination, analyses of liquid
and solid samples, and reports.
-51-
-------
In the EPA field study, sludges will be obtained
from 10 Mw lime/limestone pilot scrubbers at the TVA Shawnee
Power Station at Paducah, Kentucky, and will be placed into five
nearby ponds. One pond will receive raw lime sludge; another
will receive raw limestone sludge; the third will receive chemi-
cally conditioned lime sludge; and the last two will receive
chemically conditioned (by two different processes) limestone
sludge. Each pond will have a leachate well and a ground water
well. Tests will be performed to determine the following:
(1) the nature of the bottom soil of each pond; (2) the quality
of the water from all wells; (3) the seepage through the bottoms
of all ponds; (4) the interaction between the sludges and the
bottom soil of each pond; and (5) the quality of the chemically
conditioned sludges as to strength, permeability, and leaching
effects.
NERC-Corvallis has initiated a contract with Aerospace
Corporation directed toward determining the implications of
open-loop or partially open-loop operation of lime/limestone FGD
systems. Analyses of various sludge liquors will be performed and
technologies for liquor treatment will be evaluated Resulting
data will be used to ascertain the water pollution and reuse
potential, for various plant uses, of treated and untreated
scrubber liquors.
Two programs have recently been initiated at NERC-
Cincinnati to evaluate the environmental effects of FGD sludge
disposal. One of these is an interagency agreement with the
U.S. Army Corps of Engineers' Waterways Experiment Station in
Vicksburg, Mississippi. Under this agreement, the leachability
and durability of raw and chemically fixed hazardous industrial
wastes and FGD sludges are being studied. Five industrial
sludges and up to six FGD sludges are being obtained for the
-52-
-------
study. The FGD sludges obtained so far in the study include
the following:
Eastern (high sulfur) coal - Lime
- Limestone
- Double Alkali
Western (low sulfur) coal - Limestone
- Double Alkali
The second program is also an interagency agreement,
with the U.S. Army Materiel Command's Dugway Proving Ground,
Dugway, Utah. Under this agreement research is being conducted
to determine the extent to which heavy metals and other chemical
constituents from 13 industrial and three FGD sludges could migrate
through the soil in land disposal sites. After initial screen-
ing tests with a variety of U.S. soils, leachate column studies
will be performed with two selected (best and worst) soils.
Long-term permeability tests with selected clays are also planned
for the FGD sludges.
NERC-Cincinnati is also currently considering a full-
scale FGD sludge disposal demonstration program with an Eastern
utility.
Additional information relevant to sludge disposal has
been generated through NERC-Cincinnati efforts in mine drainage
pollution control and solid waste disposal. EPA mine drainage
activities have resulted in numerous reports dealing with sludge
produced by neutralization of acid mine drainage. The reports
cover areas such as in-situ sludge precipitation, sludge super-
natant treatment, thickening and dewatering, use of latex as a
soil sealant, and technical and economic feasibility of bulk
transport.
-53-
-------
Also, NERC-Cincinnati municipal sludge activities
relate to the EPA sludge program under discussion. Examples
include the following:
1. Methods of removing pollutants from leachate
water.
2. Evaluation of landfill liners.
3. Development of mathematical models to deter-
mine effects of landfill leachate on groundwaters.
4. Leachate pollutant attenuation in soils.
5. Moisture movement in landfill cover material.
6. Forecasts of effects of air and water pollution
controls on solid waste generation.
An attempt is being made to use the Aerospace program
as the focal point for documenting all sulfur oxide sludge
activities; close liaison is being performed by Aerospace with
NERC-Corvallis, NERC-Cincinnati, sludge-producing utilities, and
sludge treatment vendors.
III. ALTERNATIVE SULFUR BY-PRODUCTS
A number of sulfur containing by-products can be
recovered from power plant flue gas desulfurization systems.
These alternative sulfur by-products are sulfur, sulfuric acid,
gypsum, sodium sulfate, ammonium sulfate, and liquid SOn-
-54-
-------
The production technologies for recovering S02 from
such power plant flue gas desulfurization systems as sulfuric
acid, sodium sulfate, ammonium sulfate, and gypsum have been
commercially demonstrated in Japan. The production technology for
recovering elemental sulfur has not yet been demonstrated on a
power plant as an integral part of a FGD process although a
successful demonstration of sulfur production has been completed
on a smelter application. In 1975 EPA. Davy Powergas (formerly
Wellman Lord) and Allied Chemical plan on demonstrating an
integrated FGD system producing by-product sulfur at a plant of
Northern Indiana Public Service Company (NIPSCO)
Table 6 compares FGD sulfur by-products in terms of
potential quantities produced, market value, potential market-
ability, and disposal considerations.
The only alternative by-products that appear to have
a significant potential market are sulfuric acid and sulfur.
The overall problem of marketing sulfuric acid is quite compli-
cated. The problems of marketing sulfur are intimately tied to
the demand for sulfuric acid since 90 percent of the sulfur
consumed in the United States is used in the production of sulfuric
acid. There is probably a good chance that either the sulfur
or the acid market could be penetrated to a moderate extent;
this would mean that, in favorable sections such as the Midwest
and Coastal Northeast, power plant abatement sulfur or sulfuric
acid could be marketed. Due to marketing constraints, it is
estimated that not more than 50,000 Mw equivalents of sulfur or
sulfuric acid can be sold by 1980. This is comparable in mag-
nitude to about 43 percent of the expected total FGD capacity in
1980 and about 50 percent of the current market for sulfuric
acid.
-55-
-------
Table 6. COMPARISON OF ECONOMIC, MARKETING, AND DISPOSAL ASPECTS OF FLUE GAS CLEANING BY-PRODUCTS"
By-Product
Sulfur
Sulfuric
Acid
Gypsum
Sodium
Sulface
Annual Production
From 1000 Mw Generating
Plant With FGDb
(metric tons/yr)
65,300
200,000
351.000
290,000
(Produced by Wellman-
Pouer Gas process as
a purge equal to
about 5-10% of the
sulfur in the incoming
flue gas)
Current U.S.
Consumption
(metric tons/yr)
10,000,000
28,200,000
18,000,000
1,450,000
Current
Market
Price ($/
metric ton]
22-31
11-16
3-4
16-27
Maximum
FGD System
Creditc
(mills /Kwh)
0.22
0.34
0.16
0.72
Ability
to
Penetrate
Market
Fair
(Up to about
5% of market will
probably be
penetrated. Fair
chance of 10-30%
of market either
as S or H2S04
since it is
essentially the
same market.)
Good
(Excellent chance
of penetrating
75% of market.
Good chance of
penetrating 10-
30% of narket)
Questionable
(Not demonstrated
that wall board-
grade gypsum can be
made. All agricul-
tural gypsum used
in California.
Portland Cement
gypsum must be
l/4"-2" in
size. By-product
would have to be
palletized.)
Limited
(Eastern market
supplied by
present by-product
production.
Western market
equal to output
from one 1000 Mw
plant)
Alternatives for
Non-Marketable
By-Product
Store/dispose
(piles)
Store
Neutralize &
dispose as
gypsum (piles,
ponds, land-
fills)
Store/dispose
(ponds, piles,
landfills)
Store
Neutralize &
dispose as
gypsum (ponds,
piles, land-
fills)
Product Disposal-
Related Advantages/
Disadvantages As
Compared Lo Untreat-
ed Scrubber Sludge
(1) Much less hulk
(2) Less soluble
(3) Dry
(4) Potentially
flammable
(5) Potential H2S
odor problem
(6) Potential
erosion problem
(7) Susceptible to
chemical arid
biological oxida-
tion
Disposal prodvct:
gvpsum
(1) Less bulk
(2) Easier to
deuatcr
(1) Less bulk
(2) Easier to
dewater
Disposal produce:
gypsum
(1) Less bulk
(2) Easier to
dewater
Ln
ON
l
-------
Table 6 (Continued). COMPARISON OF ECONOMIC, MARKETING. AND DISPOSAL ASPECTS OF FLUE GAS CLEANING BY-PRODUCTS*
By-ProducC
Ammonium
Sulfate
Liquid
S02
Annual Production
From 1000 Mtf Generating
Plant with FGD^
(tneCtftc tons/yt)
270,000
130,000
(784,000 short tons)
Current U.S.
Consumption
(metric tons/yr)
2,400,000
86,740
Current
Market
Price ($/
metric ton^
27-35
N/A
Maximum
FGD System
Creditc
(tnms/KwhJ
1.14
N/A
Ability
to
Penetrate
Market
Poor
(66% of market
presently
supplied by by-
product from
chemical indus-
try. Projected
to increase to
.100% by 1980.)
Poor
(Production from
one 1000 Mw plant
is greater than
total U.S, market
consumption)
Possible
penetration of
fi\aA KA/| t.
synthetic aggre-
gate market.
Alternatives for
Non-marketable
By-product
Store
Neutralize &
dispose as
gypsum (ponds,
piles, land-
fills}
Store
Convert to S
or gypsum and
dispose
disposal^
(ponds)
Treated disposal
(landfill)
Product Disposal-
Related Advantages/
Disadvantages ts
Compared to l> treat-
ed Scrubber Sludge
Disposal product:
fypsum
1) Less bulk
(2) Easier to
deuater
Disposal product:
gvpsum
(1) Less bulk
(2) Easier to
de water
(1) Improved phy-
sical properties
(2) Less soluble
(3) Reduced
permeability &
teachability
t
Ul
°For references, see Volume II, Table III-7.
Assumptions: 6400 hr/yr operation, 31 S, 0.4 kg coal/Kvh, SS% SO,
removal efficiency.
Assuming LODZ sale of product at lovesC market price.
'There are potential ground and surface water pollution and land use/
reclamation problems with all disposal products shown. Untreated
scrubber sludge may have high potential for these problems.
-------
On the basis of by-product environmental considera-
tions alone, the following order of preference is suggested:
1. Sulfuric acid or sulfur for sale, if a
reliable market can be found - The preference between
the two depends on the relative production, handling.,
and shipping costs which depend on local as well as
technical factors. Generally, regenerable systems
able to sell these products are economically
competitive with lime/limestone FGD systems with
disposal costs in the ranges of $4-10/wet ton of
sludge (without ash) for lime scrubbing and $4-7/
wet ton for limestone scrubbing.
2. Sulfur for storage - Sulfur production leads to
substantially reduced quantities of the end-product
with correspondingly less land usage. Although
there may be some storage problems with sulfur, it
should be relatively easily handled compared to
sludge. It would also represent a potentially
saleable commodity, when and if sulfur demand exceeds
sulfur supply. Economics for sulfur storing
systems would be competitive with lime/limestone
systems with disposal costs greater than $7/wet ton
of sludge (without ash) for limestone scrubbing
and greater than $ll/wet ton for lime scrubbing.
Below these sludge disposal costs, the economics
of sulfur storage systems would not be competitive
with lime/ limes tone systems since they co.uld
assume no by-product credits and disposal of unmarket-
able sulfur would be an additional cost.
-58-
-------
3. Gypsum for storage - Gypsum could be a favored
end-product compared to sludge since it would
dewater more readily thereby allowing easier and less
expensive land reclamation.
4. Sludge disposal - The other by-products have
a small potential market and are difficult to store
without expensive conversion to gypsum or some
other product. For this reason they-are not
anticipated to play a major role in FGD sulfur
by-product disposal.
-59-
-------
TECHNICAL REPORT DATA
(Please read Instructions on Hie reverse before completing)
1. REPORT NO.
EPA-650/2-75-010-a
2.
3. RECIPIENT'S ACCESS!ON>NO.
4. TITLE AND SUBTITLE
Sulfur Oxide Throwaway Sludge Evaluation Panel
(SOTSEP) Final Report, Volume I—Executive
Summary .
B. REPORT DATE
April 1975
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Frank T. Princiotta, SOTSEP Chairman
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
1AR013- ROAP 21ACY-Q30
9. PERFORMING ORGANIZATION NAME AND ADDRESS
EPA, Office of Research and Development
NERC-RTP, Control Systems Laboratory
Research Triangle Park, NC 27711
11. CONTRA!
P 21A(
INT NO.
NA (In-house)
12. SPONSORING AGENCY NAME AND ADDRESS
NA
13. TYPE OP REPORT AND PERIOD COVERED
Final _____
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The report gives results of an intermedia evaluation of the environmental and
economic factors associated with disposal or utilization of sludge from non-
regenerable flue gas desulfurization processes. The evaluation was conducted
in the context of alternate sulfur oxide control techniques; existing and anticipated
air, solid waste, and water standards; and other major influences on the potential
generation of sludge, its disposal, and the magnitude of potential environmental
problems associated with its disposal. This volume gives a concise review of the
findings and technical recommendations, as well as details of each specific study
category.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
).IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Air Pollution
Sludge Disposal
Scrubbers
Flue Gases
Coal
Combustion
Electric Power Plants
Sulfur Oxides
Dust
Ponds
Earth Fills
Economics
Ur Pollution Control
Stationary Sources
tonregenerable Process
Particulates
Sulfur Byproducts
13B
07A
21B
21D
10B
07B
08H
13C
05C
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. Or PAGES
72
20. SECURITY CLASS (Thispage)
Jnclassified
22. PRICE
EPA Farm 2220-1 (9-73)
-60-
------- |