EPA-650/2-75-010-B
       April 1975
Environmental  Protection  Technology Series



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                               EPA-650/2-75-010-b
               SULFUR OXIDE
           THROWAWAY  SLUDGE
      EVALUATION  PANEL (SOTSEP),
                 VOLUME  II:
FINAL  REPORT  -  TECHNICAL DISCUSSION
                  Frank T. Prmciotta
                  SOTSEP Chairman
                Control Systems Laboratory
            National Environmental Research Center
           Research Triangle Park, North Carolina 27711
                  ROAP No. 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

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                       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.  SOCIOECONOMIC 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-b
                                 11

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                      TABLE OF CONTENTS

                                                        PAGE
                                                    Vol.1  Vol.11

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 SO
                                            X
              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

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               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

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                            TABLES

Table
 No.                          Title
 1-1      New Source Performance Standards (NSPS)  for
          Fossil Fuel-Fired Steam Generators >250  x 106
          Btu/hr 	   3

 1-2      National Ambient Air Quality Standards (NAAQS)
          for SO 2	   3

 1-3      Typical State Implementation Plans for Exist-
          ing Boilers in States Using Coal 	   4

 1-4     .Installed Generating Capacity and Net Genera-
          tion in the Electric Utility Industry (1971
          Actual and Projected to 1980) 	   5

 1-5      Economic Estimates for S02  Control Alterna-
          tives  (1974 Dollars)	  32

 1-6      Planned and Operating Full  Size Flue Gas
          Desulfurization Facilities  in the United
          States 	  42

 1-7      Typical Sludge Production Parameters	  58

 1-8      Typical Quantities of Ash and Sludge Produced bv  a
          1000 Mw Coal-Fired Generating Station Con-
          trolled with Lime/Limestone Flue Gas Desul-
          furization Systems,  Short Tons Per Yeara	  60

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                       TABLES (Continued)

Table
 No.                          Title
 1-9      Comparative Land and Soil Waste Impact of
          1,000 Mw Electric Energy System (0.75 Load
          Factor) (Low Levels of Environmental Con-
          trols Except for Installation of a Limestone
          FGD System for SO  and Particulate Removal)	  63

 I-10     Comparison of Major Solid Waste Disposal
          Problems	  65

 I-11     Characteristics of Sludge From Operating
          S02 Scrubbers 	  78

 1-12     Chemical Composition of Typical Desulfuriza-
          tion System Sludge 	  79

 1-13     Power Plant Coal Ash Compositions  	  80

 1-14     Selected Trace Elements  in Coals and Ash 	  82

 1-15     Ash Leachate Compositions  From Power Plants
          Burning Acidic and Alkaline Coal    	  83

 1-16     Analyses of Dry Fly Ash  Solids  From the
          Y-12 Steam Plant   	  84

 1-17     Chemical Analyses  of Ash Pond Discharge
          From TVA' s  Widows  Creek  	  86

 1-18     Selected Elements  in Solution    	  87
                               vi

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                      TABLES (Continued)

Table
 No.                          Title                       Page
 1-19     Spark Source Mass Spectrographic Analysis
          of Scrubber Solids 	 88

 1-20     Emission Spectrographic Analyses of Lime-
          stone and Clarifier Liquor and Solids 	 89

 1-21     Emission Spectrographic Analysis of Solids
          From a Western Station 	 91

 1-22     Spark Source Mass Spectrometry Analysis of
          Solids From a Western Station 	 92

 1-23     Chemical Analysis of Sludge Liquors   	 93

 1-24     Wet Sieve Analysis of Scrubber Sludges 	 98

 1-25     Subsieve Analysis of Fly Ash and an Eastern
          Coal Lime Scrubber Sludge 	 99

 1-26     Subsieve Analysis 	 99

 1-27     Elaine Indices for Scrubber Sludges 	100

 1-28     Gel Strengths of a Limestone System Sludge	102

II-l      Ash Collection and Utilization Year 1971 	124

II-2      Characteristics of Sludge From Operating
          S02 Scrubbers 	126
                               vii

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                      TABLES (Continued)

Table
 No.                          Title
II-3      Sludge Treatment/Disposal Techniques for
          Selected Utility Lime/Limestone FGD Systems	134

II-4      Summary of Commercial Slurry Pipelines 	151

II-5      Preliminary Estimate of Costs of Potential
          Liners for Sanitary Landfills. Polymeric Mem-
          branes - Plastics and Rubbers   	158

II-6      Preliminary Estimate of Costs of Potential
          Liners for Sanitary Landfill Soils, Admixcure Mate-
          rials , and Asphalt Membranes 	159

II-7      Summary' of Sludge Dewatering Techniques	171

II-8      Summary of Short-Term Centrifuge Tests
          at EPA Limestone Test Facility at Shawnee 	176

II-9      Centrifuge Tests - Pilot Plant Sludge 	177

11-10     Comparison of Dewatering Techniques for
          Limestone Scrubber Sludges 	178

11-11     Results of Tests of Selected Stabilized
          Road Base Mixtures Prepared at Dulles
          Airport Transpo 72 Project 	199

11-12     Laboratory Results of Fixed TVA Limestone
          Sludge Analysis 	200
                              viii

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                     TABLES (Continued)

Table
 No.                          Title                        Page
11-13     Atomic Absorption Tests for Leachable Ions
          on Selected Specimens Subjected to 48 Hour
          Shaking Test 	202

11-14     Chemical Constituents of Stabilized De-
          sulfurization System Sludge Leachate   	203

11-15     Chemfix Preliminary Leaching Study, Lab
          Leachate of 2/28/73 Field Chemfix Product
          Illinois Power Plant   	204

11-16     Chemfix Preliminary Leaching Study,  Lab
          Leachate of 9/14/73 Lab Chemfix Product   	205

11-17     Sludge Analysis 	207

11-18     Leachate Analyses From Sludge Samples S-l
          Through S-6 	208

11-19     Leachate Analyses From Commercial Product
          (Sintered or Roasted Dewatered Sludge) 	209

11-20     Leachate Analyses From Commercial Product
          (Sintered or Roasted Dewatered Sludge) Dif-
          ferent Lime Composition 	210

11-21     Pilot Plant Sludge with Different Quantities
          of Hardening Additive   	211
                               ix

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                       TABLES  (Continued)

 Table
  No.                          Title                        Page
 11-22     Atomic Absorption Tests Made on Surface
           Runoff of a Stabilized Fly Ash/Sludge
           Mixture   	213

 11-23     Runoff Analyses From Sintered Processed
           Sludge   	214

 11-24     Physical Properties of Transpo 72 Base
           Course Compositions 	222

 II-25     Results of Field Tests Showing Comparison
           of Poz-0-Pac and Poz-0-Tec Formulations 	223

III-l      Contingency Forecasts of Demand for Sulfur
           (All Forms)  by End Use,  Year 2000 	252

III-2      Sulfuric Acid End Use Pattern 1970 	256

III-3      Sulfuric Acid Plant Capacity 	258

III-4      U. S. Gypsum Statistics  (Thousands Short
           Tons) 	262

III-5      Production Statistics for the Sodium Sul-
           f ate Indus try	•	265

III-6      U. S. Ammonium Sulfate Production and
           Inventory Levels 	268

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                       TABLES (Continued)

 Table
  No.                          Title
III-7      Comparison of Economic, Marketing, and
           Disposal Aspects of Flue Gas Cleaning
           By-Pro ducts	276

III-8      Comparison of the Amount of Limestone
           Sludge,  Sulfur,  and Gypsum that can be
           Produced by a 1000 Mw Coal-Fired Generating
           Station 	279
                                xi

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                           FIGURES

Figure
  No.                        Title

 1-1      Process Cost Comparison for Nonregenerable
          and Regenerable Flue Gas Desulfurization
          Systems--Effect of Sludge Disposal and By-
          Product Sales or Disposal (Without Fly Ash)	 36

 1-2      Coal-Fired Generating Stations Over 200 Mw
          in the United States	 46

 1-3      Cumulative Need:  FGD For Coal-Fired Power
          Plants	 50
            /
 1-4      Cumulative Need and Vendor Capacity	 53

 1-5      Sludge Compaction Strength	104

 1-6      Settling Test for Untreated FGD Sludge 	108

II-l      Installed Liner Costs	160

II-2      Disposal Costs - Ponding Sludge,  50 Percent
          Solids (30 year average)	161

II-3      Schematic Diagram of Poz-0-Tec Process	185

II-4      Typical Hauling Rates for Stabilized Fly Ash
          Compositions	:	193

II-5      Comparison of Poz-0-Pac and Poz-0-Tec Permeabil-
          ity Values	198

II-6      Penetration Resistance for a Typical Fly Ash/
          Calcium Sulfate/Lime Mixture	219
                              xii

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                     FIGURES (Continued)
Figure
 No.                         Title
 II-7    Compressive Strength for a Typical Fly Ash/
         Calcium Sulfate/Lime Mixture         	221

 II-8    Effect of Percent Dravo Additive on Shearing
         Strength           	224

 II-9    Effect of Solid Content and Percent Dravo
         Additive on the Strength          	225

 III-l   Location of Major Coal- and Oil-Fired Power
         Plants	250

 III-2   Sulfuric Acid Manufacturing Capacity         ....257
                             xiii

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                           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)
                              xiv

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          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:
                               xv

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           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
                                               Jt
           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
           S02, 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
                               xvi

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back-up information and references for the Volume I Technical
Discussion Summary.

          Because of time constraints, SOTSEF activities were
streamlined by working in accordance with the following
groundrules:

          1.   The scope of the activities focused
              primarily on SOX and particulate
              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.
                             XVII

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                       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.
                             xvi 11

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                   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
           1 Btu
           1 Btu
           5/9 (°F-32)
           1 ft
           1 ft2
           1 ft3
           1 yd
           1 yd?
           1 yd3
           1 mile
           1 mile2
           1 acre
           1 pound
           1 ton (short)
          Metric
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
                              xix

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                 I.	DEFINITION OF THE PROBLEM
A.        AVAILABILITY OF ALTERNATIVE SO  CONTROL TECHNOLOGY
          	.—x	

1.0       Introduction
          Recent air quality legislation such as the Federal
Air Quality Act of 1967 and the Clean Air Amendments of 1970
have had, and will continue to have, a decided impact on the
demand for sulfur oxide control equipment and new sources of
clean fuels for the electric utility industry.  Legislation
has been promulgated at the federal, state, and local levels to
control emissions of air pollutants from mobile sources and
significant stationary sources.  Emissions of sulfur oxides
(S0>:), nitrogen oxides (NOX), and particulates are of particular
concern to fossil fuel-fired power plants, since power plants
are the largest stationary sources, both individually and col-
lectively, of all three pollutants.  This section deals spe-
cifically with SOX emissions, which are about 97 percent sulfur
dioxide (S02).

          Barring any relaxation of the current regulations,
fossil-fueled generating stations, for which construction was
initiated after about January 1971, will have to bring stack
gas emissions of S02, N0x> and particulates within prescribed
New Source Performance Standards (NSPS).   Furthermore, all
states have established regulations that require control of S02
and particulates (and in some cases NO )  from existing sources.
The principal target date of state programs is July 1975,
when primary national ambient air quality standards (NAAQS)
are to be achieved.   Secondary NAAQS are more stringent than
primary standards in the case of particulates and S02 and,

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therefore, require more effective control of source emissions.
Secondary NAAQS must be attained in a reasonable time.  Table 1-1
lists EPA NSPS for S02 emissions from fossil fuel-fired steam
generators; Table 1-2 lists NAAQS for S02.  Table 1-3 presents
typical state/local limits on S02 emissions from State Imple-
mentation Plans (SIP) for meeting NAAQS.

          The problem of reducing S02 emissions is heightened
by the needs of the Nation's utility industry to meet the spiral-
ing demand for electric power generation.  According to a
scenario developed by the U. S. Department of the Interior (USDI)
in December 1972, the growth in net energy consumption is
reflected by the growth in the Nation's electric generation
sector from 1.61 billion megawatt-hours (Mwh) in 1971 to 2.13
and 3.00 billion Mwh in 1975 and 1980, respectively (Ref.  1).
Predicted trends among these three energy types, fossil fuel,
nuclear, and hydropower, are illustrated in Table 1-4.  Although
the percentage of the total energy generation burden supported
by fossil fuels will begin to decrease as nuclear power becomes
available, the total installed generating capacity of fossil-
fueled boilers is expected to increase from 303 to 445 thousand
Mw by 1980.

          This section addresses the problem of generating this
additional 140 thousand Mw of electricity, as well as that from
plants already on stream,  in a manner consistent with current
federal, state, and local air quality control regulations  for
SOa.   To accomplish this,  a number of alternatives are available.

          One of these,  of course,  is the direct burning of
naturally available clean fossil fuels;  i.e., low-sulfur coal
and oili and natural gas.   However,  it is recognized that  clean
fuel supplies are not available in quantities needed for present

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Table 1-1.  NEW SOURCE PERFORMANCE STANDARDS (NSPS) FOR FOSSIL
         FUEL-FIRED STEAM GENERATORS > 250 X 106 Btu/hra
Fuel Type
Maximum Allowable Emissions for
    (grams/1000 Kg-calories)
  Coal
  Oil
              2.2
              1.4b
j
 Reference 1
 Not to be exceeded more than once a year.
  Table 1-2.   NATIONAL AMBIENT AIR QUALITY STANDARDS (NAAQS)
                           FOR S00
Averaging
Time
Annua I
24 Hour3
3 Hour
Primary
o
ug/nr
80
365

ppm
0.03
0.14

Secondary
o
ng/m
60
260
1300
ppm
0.02
0.1
0.5
 Not to be exceeded more than once a year,

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          Table 1-3.  TYPICAL STATE IMPLEMENTATION PLANS
            FOR EXISTING BOILERS IN STATES USING COAL3
State
Ohio
Tennessee
Kentucky
Alabama
Michigan
Pennsylvania
West Virginia
Illinois
Regulation (or Equivalent)
(Ib S02/106 Btu Fired)
1.0b
It5b,c,d
1.2e'f
1.2c'f
1.0d'f
0.6 to 1.0 (depending on size)
2.7£
1.8*
a
 lAs of June 1973
^Effective July 1, 1975
"Under revision
 Regulations in different terms
^Effective July 1, 1977
 Less stringent in some areas of the state

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  Table 1-4.
INSTALLED GENERATING CAPACITY AND NET GENERATION
  IN THE ELECTRIC UTILITY INDUSTRY
(1971 Actual and Projected to 1980)a
Period: Type of Plant
1971:
Fossil Fuel Burning Plants
Nuclear Plants
Hydropower Plants
TOTAL
1975:
Fossil Fuel Burning Plants
Nuclear Plants
Hydropower Plants
TOTAL
1980 :
Fossil Fuel Burning Plants
Nuclear Plants
Hydropower Plants
TOTAL
Installed
Generating
Capacity,
Mw

302,810
8,687
55,898
367,395

350,000
50,000
80.000
480,000

445,000
120,000
95,000
660,000
Load
Factor

0.50
0.50
0.55
0.51

0.50
0.55
0.50
0.51

0.50
0.60
0.50
0.52
Net
Generation ,
Billion Kwh

1,310
38
266
1,614

1,540
240
350
2,130

1,950
630
420
3,000
% of
Total

81.2
2.3
16.5
100.0

72.3
11.3
16.4
100.0

65.0
21.0
14.0
100.0
USDI (Reference 1)

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and projected needs.  In light of the clean fuel deficit, a
number of potential approaches to utilizing high sulfur fuels
as energy sources are being investigated.  The technologies
under consideration are as follows:

          1.  Physical coal cleaning
          2.  Chemical coal cleaning
          3.  Desulfurization of oil
          4.  Flue gas cleaning
          5.  Fluidized bed combustion
          6.  Coal gasification (high heat value
              (HV) gas)
          7.  Coal gasification (low HV gas)
          8.  Coal liquefaction

These technologies for utilization of high sulfur fuels are
discussed in Section 3.0.

2.0       Impact of Fuel Switching and Supplementary Control
          Strategy on Supply

          In light of the difficulty new generating stations
are experiencing in obtaining long-term supply contracts from
coal companies,  many new plants are being designed-for multi-
fuel operation.   That is, they are equipped t'o fire more than
one fuel type—usually coal and oil or gas and oil.  If the
supply of a utility's major fuel type is curtailed ''temporarily,
spot reserves of the secondary fuel may be tapped to fill the
void.

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          Two EPA-initiated plans may provide some existing
power plants with relief from extremely stringent S02 emission
restrictions.  These are:  (1) the Clean Fuels Policy enunciated
by former EPA Administrator Ruckelshaus in a letter to all state
governors; and (2) the use of supplementary control systems as
an interim measure until adequate constant control measures can
be applied.  It is emphasized that both approaches apply only
to existing sources and would have no effect on federal emission
standards for new steam generators.

          The Clean Fuels Policy was developed in recognition
of the low-sulfur fuels deficits.  Evaluation of state S02 emis-
sion limitations indicates that in at least some areas greater
restrictions are being imposed on existing sources than are
necessary to meet primary NAAQS.   Consequently, Mr. Ruckelshaus
informed all state governors in December 1972, that they should
review implementation plans and consider revisions with the aim
of meeting only the health-oriented primary NAAQS by July 1975.
To date there have been few state actions to relax S02 emissions
from fuel burning sources.   Nevertheless, several are under
consideration.   For example,  the State of Ohio restricts S02
emissions from all power plants to the equivalent of coal con-
taining 0.6 percent or lower sulfur content.  This regulation
was enacted even though many areas of Ohio do not require such
stringent control to meet either primary or secondary NAAQS.
As a result of current litigation, state officials have indicated
that they intend to set compliance schedules and revise S02
emission limits where necessary such that NAAQS can be realized
through a more  realistic program.

          Realization of the Clean Fuels Policy objectives will
require information concerning air quality in the vicinity of
power plants.   Since much of this information is now lacking,

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 judgments  frequently  cannot be made as  to  the degree of S02
 control  required  to meet NAAQS.   In addition, some states may
 not  decide to  initiate necessary  changes in regulations.  The
 Clean Air  Act  clearly allows  states and local jurisdictions to
 establish  air  pollution control regulations which are more
 restrictive  than  necessary to meet federal standards (NAAQS
 and  new  source performance standards).

           Application of supplementary  control systems involves
 the  use  of measures such as temporary fuel switching (to low
 sulfur fuel) or decreasing boiler load  to curtail the rate of
 emissions  from a  source when meteorological conditions conducive
 to high  ground-level  pollutant concentrations exist or are
 anticipated.   This approach is considered a stopgap measure to
 attain and maintain national standards without unduly disrupting
 production of  important products  (particularly nonferrous metals)
 and  electric power plants.   It would serve in the interim until
 stack gas  cleaning hardware has been designed, built,  and
 installed  or new  sources of fuel have been developed.

           It is unlikely,  however, that supplementary control
will have  significant impact on the clean fuel supply/demand
balance  since  the tentative EPA amendments prohibit its use for
 sources where other control options are available.   This pro-
vision would preclude its  use for oil-fired steam generators
and  for new steam generators of all types.   Coal-fired electric
generating plants may be permitted use of supplementary control
only if not to do so would either delay attainment  of the
national standards or permanently curtail power production.

3.0       Technologies for Utilization of High Sulfur Fuel

          Methods available or being developed to utilize high
sulfur fuels for energy while complying with environmental

                              8

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regulations include a variety of techniques which vary widely
from the standpoint of complexity and stage of development.  The
methods can be divided logically into the following eight classes
or technologies which are discussed below:

          1.  Physical coal cleaning
          2.  Chemical coal cleaning
          3.  Desulfurization of oil
          4.  Flue gas cleaning
          5.  Fluidized bed combustion
          6.  Coal gasification (high HV gas)
          7.  Coal gasification (low HV gas)
          8.  Coal liquefaction


Comparative economics of these technologies are discussed in
Section 4.0.

          3.1  Physical Coal Cleaning

          Since the late 1960's EPA has supported work to define
the usefulness of available coal cleaning methods for removal
of sulfur from coal.   Such methods involve crushing coal to
about 1 cm (3/8 inch) or less to liberate pyritic sulfur and
passing it through equipment which separates the high density
fraction where pyrite is concentrated.   To date coals from over
300 mines have been tested.   Fifteen to 20 percent of the coal
supplies are capable  of being cleaned to less than 1 percent
total sulfur.   The average reduction for all coals tested was
30 percent.   For many, 50 percent reductions were possible.  It
is not possible to reduce sulfur in many coals to the very low
levels required by some control regulations.  However, physical

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coal cleaning is a low cost control technique utilizing readily
available hardware which will be useful with cleanable coals,
either alone or in combination with other methods such as flue
gas cleaning.

          3.2  Chemical Coal Cleaning

          Chemical coal cleaning processes are designed to
remove pyritic sulfur, organic sulfur, or both from the coal.
Two processes appear to be worthy of note.

          One process for the removal of pyritic sulfur from
coal utilizes the reaction of ferric ion with the pyritic sul-
fur (Meyers Process developed by TRW).  The system may obtain
95-100 percent removal of pyritic sulfur.  To date effective
removals have been obtained using coal up to 0.65 to 0.75 cm
size.   More effective (time-wise) removal is seen at the 149
micron (100 mesh) size.   If extremely fine size coal is required,
agglomeration after cleaning may also be required in the process.
          The above process does not alter the nature of the
coal.  In addition, this process is scheduled to be in pilot
operation during fiscal year 1974.   An estimate for commercial
utilization is premature at the point, but the application is
a minimum of 5 to 6 years away.
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          3.3  Desulfurization of Oil

          Several commercial processes are available for de-
sulfurizing distillate crude and residuum to various levels of
required sulfur content.  The most desirable process in any
situation is a function of the feedstock characteristics and
sulfur level required in the end product.

          Desulfurization processes basically involve reaction
of the sulfur in the oil with hydrogen in a catalytic reactor
usually at high temperatures and pressures.  A major variation
in the processes involves the fraction of the crude that is
hydrodesulfurized:  atmospheric gas oil distillate, atmospheric
residuum, vacuum gas oil distillate, or vacuum residuum.

          One approach offered by several companies is that of
desulfurizing the vacuum gas oil and blending the desulfurized
distillate with the high sulfur vacuum residuum.  This type of
operation is capable of producing a product of 1.0 to 2.5 percent
sulfur (Ref. 2).

          Hydrodesulfurization of the atmospheric residuum,
which contains the vacuum distillate and vacuum residuum
fractions,  can yield a product of lower sulfur levels, 0.3-1.0
percent;  however,  to reach the very low sulfur levels of 0.3
percent and lower, the heavy vacuum residuum must be desulfurized
(Ref. 2).  Desulfurization of heavy residual oils requires more
complex processing to cope with the fouling and coking tendencies
of the difficult feeds.

          One process that deals with this problem is Exxon
Research and Engineering Company's Flexicoking Process.   Flexi-
coking involves coking the heavy residuals to form a distillate
                              11

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 gas  oil  and  then gasifying  the  coke which contains the sulfur.
 The  sulfur,  present as H2S,  is  removed  in a sulfur recovery
 unit and the resultant gas  may  be used  in furnaces or boilers.
 The  first  commercial Flexicoker is being constructed in Japan
 with a capacity of 22,000 bbl/day.  It  is scheduled for start-
 up in 1976.   Since April 1974,  a prototype, 750 bbl/day Flexi-
 coker has  been processing various feeds at the Exxon Company,
 USA,  refinery in Baytown, Texas.  Performance has equalled or
 surpassed  expectations (Ref. 3).

           Other processes for desulfurizing residual oils involve
 the  development and use of  poison-resistant catalysts in the
 reactors used for hydrodesulfurization.

           3.4 Flue Gas Cleaning

           Since 1967 considerable work has been underway to
 develop  systems to remove S02 from power plant effluent gases.
 Processes which have been developed to remove S02 from power
plant stack gases can be generally divided into two categories--
 "throwaway" and "by-product recovery."  Throwaway processes
 involve S02 absorption and combination with some cation (generally
 calcium,  sodium,  or ammonia).  This combination is precipitated
as a  solid and disposed of as a waste material.   In by-product
recovery processes,  flue gas S02 is absorbed,  recovered,  and
then marketed in the form of liquid or gaseous S02,  sulfuric
acid, elemental sulfur,  sodium sulfate or ammonium sulfate.

          The majority of full-size power plant desulfurization
systems in both the planning and operational phases  involve
lime or limestone wet scrubbing systems.  These processes will
be discussed at some length in this section with regard to
principles of operation,  status of development,  operability,
                              12

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and reliability   A number of by-product recovery processes
are currently undergoing investigation at both the pilot plant
and full-scale levels of development.  The more advanced of
these systems will be examined in the sections following.

          3.4.1  Lime/Limestone Wet Scrubbing Technology -
Throwaway processes using lime and limestone as the alkaline
absorbent have been the target of the greatest part of the
research and development efforts in SOZ control.  Primary reasons
for this are that these processes are more fully characterized
than other first generation systems, have relatively low capital
and operating costs; and have relatively high potential removal
efficiencies (90-95 percent).

          Two basic types of wet limestone processes have been
developed:  (1) boiler injection of the limestone followed by
wet scrubbing,  and (2) addition of limestone into the slurry
handling system (tail-end scrubbing process).

          The boiler injection plus wet scrubbing process has
been extensively tested on a commercial scale by Combustion
Engineering, Inc.  (CE) since 1968.   After 4 years of intermittent
operation due to numerous technical difficulties, CE no longer
offers this process in favor of the lime/limestone tail-end
scrubbing process.

          In the tail-end addition process, lime or limestone
is added directly to the slurry circuit rather than injected
into the boiler.   The overall  reaction in the scrubbing system
involves gaseous SC>2  and C02 reacting with CaO or CaC03 to give
solid CaC03  %H20,  CaSO,,  2H20,  lime or limestone, and fly ash
from the system.
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           The  first  full-scale  installation  in  this  country
 that  utilizes  limestone  introduced  into  the  scrubbing  circuit
 is  the  175 Mw  Commonwealth Edison Will County Station  - Unit
 No. 1.  This unit was  started up in February 1972, and has
 operated  intermittently  since then,  achieving S02 removal
 efficiencies in  the  range of 75 to  85 percent.  The major prob-
 lems  experienced to  date have involved demister pluggage with a
 soft, mud-like substance, system reliability due to mechanical
 problems,  and  uneconomic disposal of waste sludge (Ref. 4).  A
 great deal has been  learned in  the  past year, however, at the
 Will  County Unit concerning practical operating problems with
 limestone  scrubbing; during 1974 the availability of one of
 the two modules  steadily increased.  None of the problems en-
 countered  at this unit appears to be insurmountable.

          Additional valuable information concerning operation
 of lime/limestone scrubbing processes is being gathered at the
 versatile EPA prototype test facility at the TVA Shawnee Steam
 Plant.  The 30 Mw facility includes  three types of 10 Mw (equiv-
 alent) scrubbers (venturi,  TCA,  and marble bed), extensive
 process instrumentation,  and sophisticated data acquisition
 and handling systems.  Water and soda ash and short-term lime
 and limestone testing have been completed; long-term reliability
 limestone and lime testing are in progress (Ref. 5).

          The most recent successful operation of a lime wet
 scrubbing process is the 65 Mw installation at Louisville Gas
and Electric Company's Paddy's Run Station.   The unit uses
carbide sludge [Ca(OH)2]  as the  alkaline absorbent.   No scaling
or plugging problems have been encountered in over 3000 hours
of closed-loop operation since April 1973.  The system demon-
 strated near 100 percent  availability during the last 4 months
of 1974 while removing 80 to 90  percent of the flue gas from
                              14

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 boilers  fired with  1.5  to 4.0 percent  sulfur coal  (Ref.  6).
 Waste  sludge is  thickened,  filtered and disposed of as untreated
 landfill;  fly ash is  sporadically mixed in by bulldozers at the
 disposal site.

           Much of the developmental work with the  lime scrubbing
 system has been  conducted in Sweden and Japan.  The A. B. Bahco
 system, which utilizes  a two-stage inspirating scrubber, is con-
 sidered an important  operational scrubber facility despite its
 small  size (the  equivalent  of about 25 Mw for the  three units).
 The system has been operating routinely at 95 to 98 percent S02
 removal on three oil-fired  boilers at a Stockholm hospital.
 The unit is considered  among the more successful wet lime scrub-
 bers although periodic  shutdowns are necessary to remove hard
 sulfate scale in the  demister section.  The demisters have not
 been equipped with washing  sprays, a possible solution to the
 scaling problem.  Research-Cottrell is the U.S.  licensee for
 the Bahco  process and is offering modules up to 40 Mw.  EPA
 has recently entered  into an agreement with the Air Force for
 a Bahco process test program to be conducted on a seven-boiler
 installation with a total 25 Mw (equivalent) capacity.

           In Japan the  156 Mw power plant of the Mitsui Aluminum
 Company has been retrofitted with two Chemico dual-stage venturi
 scrubbing  systems, each capable of handling 75 percent of the
 full load  gas flow.   The system has demonstrated reliable,
 trouble-free operation  since being put on stream in March 1972.
The plant  is presently burning 2 percent sulfur coal (1800 to
 2200 ppm inlet S02)  and achieving 80 to 85 percent S02 removal
 from the flue gas using carbide sludge as the alkaline absorbent.
 Since coming on stream,  the system has operated at near 100
percent availability.   The absence of scaling difficulties  has
been attributed to operational know-how developed by Mitsui in
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 extensive pilot plant tests  (in Japan)  and precise pH control.
 To date the Mitsui  system is  the most successful  operating unit
 based on a throwaway process  (Ref.  4).

           A survey  of the seven companies  with  experience  in
 full-scale tail-end wet  scrubbing shows that most companies will
 provide S02  removal quantities  varying  from 70  to 90  percent,
 or as required  to meet EPA standards  (Ref.  4).  A number of
 important design variables have changed in range  since  the
 first systems were  built 5 years  ago.   The liquid to  gas ratio
 has  increased from  35 liters/1000 N cubic  meters  (10  gal,/1000
 acfm)  to as  high as 350  liters/1000 N cubic meters  per  hour
 (100  gal./lOOO  acfm),  with the  average  being near 210 liters/
 1000  N cubic meter  per hour (60 gal./lOOO  acfm).   Stoichiometry
 has  decreased to near 1.0 from  a  former average near  1.75  based
 on S02  absorption.   Values for  both weight  percent  solids  in
 the  scrubbing slurry and hold tank  residence times  vary among
 suppliers  but the general trend has been toward higher  values.
 Systems  can  be  designed  for units  firing from 0.5  to  4.0 percent
 sulfur  fuel  and ranging  in size up  to 800 Mw.   Module designs
 are  limited  to  about  150  Mw (Ref. 4).

           3.4.2  Magnesium Oxide  Scrubbing  - All  of the magnesia-
 based  (MgO)  processes may be classified as  by-product recovery
 in that  they produce  sulfur-based products  (H2SOn or  liquid
 S02) which do not contain the additive  (MgO).

           In the Chemico-Basic  Chemicals version of the process,
 flue gas containing S02 and fly ash passes  into a venturi
 scrubber where  fly ash is  removed by scrubbing with recirculated
water.  A bleed  stream from the scrubber is thickened to con-
 centrate the fly ash and  transported as a slurry underflow to
 the disposal area.   Overflow from the thickener is returned to
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 the scrubber circuit.   Flue  gas  leaving  the  particulate  removal
 system enters a second  venturi absorber  where  it  contacts  a
 slurry of MgO and recycled MgS03,  and  MgSO,,  and unreacted  MgO'
 are separated from the  mother liquor.  Mother  liquor  is  recycled
 to  the scrubber and the centrifuged wet  cake is dried in a rotary
 kiln.   Dried anhydrous  crystals  are sent to  a  central plant
 where  they are calcined to recover MgO and S02.   The  MgO is  re-
 slurried  to maintain S02  sorption  in the scrubber.

           Chemico-Basic Chemicals  is the leading  developer of
 the MgO process,  based  on the EPA  cofunded system installed  on
 a 155  Mw  oil-fired unit of Boston  Edison's Mystic Station.   Re-
 generation of MgO and production of HzSO,, is being carried out
 at  Essex  Chemical Company.  A similar  system has  been installed
 to  treat  100 Mw  (equivalent) of flue  gas from a  coal-fired
 boiler at  Potomac Electric and Power's Dickerson  No.  3 Unit.  The
 Dickerson  plant has  shown low, but improving, reliability  with
 88  to  96 percent  S02 removal.  The availability to the boiler
 was  60 percent  for the  months of August  to November of 1974
 (Ref.  7).

           Experience with the MgO process to date has been
 encouraging  but not wholly without problems.   Because of various
 equipment  problems,  the Boston Edison installation operated only
 20 percent of the  time between April 1972 and June 1973.    Since
 that time, however,  the system has demonstrated considerably
 improved reliability.   In the period of April 12  to May  10,
 1974,  623 hours were logged at almost 100 percent  availability.
 Since  February 22, 1974, availability of the  system to the
boiler has been about 80 percent  compared to  50 percent for the
year from June 1973 to June 1974  (Ref.  8). A major technical
problem encountered with this system concerns oxidation of
                              17

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sulfites to sulfates, thereby reducing regenerator efficiency.
The S02 removal appears to be easily accomplished in the process.
Some additional problems may arise with loss of reactivity of
frequently regenerated absorbent, but this question can only be
resolved with longer periods of continuous operation.

          3.4.3  Wellman-Lord Process - Several developers have
turned to sodium-based processes for flue gas desulfurization
because sodium has a high affinity for S02 and the sulfite/
bisulfite equilibrium can be adjusted to facilitate absorption
and regeneration.

          In the Wellman-Lord process (offered by Davy Powergas),
the most technically advanced of the sodium-based processes,
flue gas from the boilers is first washed by a prescrubber to
remove the greater part of the solids from the gas.   The flue
gas passes to an absorber where S02 is absorbed into a solution
of sodium sulfite, bisulfite, and sulfate.  The S02  combines
with the sulfite to form bisulfite or else undergoes oxidation
to form sulfate.  Exiting the scrubber,  the absorbent is heated
in an evaporative crystallizer with steam to yield 90 percent
S02 gas and sodium sulfite crystals which are recycled.   The
high purity, high concentration S02 gas can be further processed
to liquid S02,  sulfur, or H2S(\.   Sulfate formed in the scrubber
by oxidation cannot be regenerated and is removed from the sys-
tem by direct purging or selective crystallization of sodium
sulfate.

          The major problem with the Wellman-Lord process is
its sensitivity to buildup of contaminants necessitating bleed.
The major contaminants are sodium sulfate, thiosulfate,  and
polythionates formed either by oxidation in the scrubber or a
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 disproportionation  reaction  in  the  evaporative  crystallizer.
 In  Japanese  installations  these waste  products  are  discharged
 to  the  ocean.  Additional  treatment will probably be  required
 for application  in  the United States.

          A  significant  demonstration  of Wellman-Lord tech-
 nology  is by Mitsubishi  Chemical Machinery at the Japan  Synthetic
 Rubber's Chiba Plant.  This  unit has operated at almost  100
 percent availability during  the past 3 years while  removing
 better  than  90 percent of  the S02 from a 75 Mw  equivalent oil-
 fired boiler flue gas stream containing 600-2000 ppm  S02.  The
 main disadvantage of the system is  the requirement  to  bleed a
 waste liquor stream due  to sulfate  formation.   A hew  unit at
 the Chubu Electric's Nishingoya Plant has reduced this purge by
 a factor of  4.  This unit has been  operating reliably  on a 200
 Mw peak-shaving unit since May  1973.

          EPA is currently co-funding construction  of  a Wellman-
 Lord process installation on the 115 Mw Northern Indiana Public
 Service Company's Mitchell Station  in Gary, Indiana.  A 1-year
 demonstration is planned with start-up scheduled for  late 1975.
 This will be the first application  of the Wellman-Lord process
 to coal-fired boilers.   The plant will also demonstrate the
 technology for reduction of S02  to  elemental sulfur with an
 integrated Allied Chemical Company process.

          3.4.4  Catalytic Oxidation Process - Two distinct
 catalytic oxidation (Cat-Ox)  schemes are available.   The reheat
Cat-Ox system is an add-on unit  designed for use on existing
power plants.  The integrated Cat-Ox systen,  on the other hand,
is for incorporation into the design of new power plants.
                               19

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           In the reheat  system, particulate removal from the
hot flue gases from  the  boiler is accomplished by a high ef-
ficiency electrostatic precipitator.  In preparation for catalyst
conversion, the flue gas stream is heated by a series of oil-
or gas-fired reheater burners and heat exchangers.  At proper
temperature (454°C (850°F)) for improved reaction kinetics,
the flue gas is sent to  a fixed bed converter where S02 is
oxidized to S03 in the presence of a V205 catalyst.  Sulfuric
acid is formed by contacting the S03 rich gas with water in an
absorption tower after the gas has been cooled by heat exchange.
The product acid (75 to  85 percent sulfuric) is cooled and sent
to storage.  Flue gases  are vented to the atmosphere after
passing through a fiber-packed mist eliminator.  The process
removes essentially all particulate matter and 85 percent of
the inlet S02.

          The integrated Cat-Ox system does not require reheat
procedures because the overall design of the plant provides for
the flue gases to exit the boiler at the conversion temperature.
The gases go immediately to the converter after electrostatic
precipitation to remove ash.  After the converter, the energy
of these hot gases is utilized in a heat exchanger section,
which consists of an economizer and an air heater.  Other process
steps are nearly identical.  In this process,  90 percent of the
S02 and essentially all particulate matter are removed.

          Pilot plant work on this process was begun in 1961.
A prototype (15 Mw) unit was installed at Metropolitan Edison's
Portland Station in 1967, removing 90 percent of the S02.   EPA,
Monsanto (the process developer),  and Illinois Power Company
have been involved in the installation of a reheat demonstration
plant on a 100 Mw boiler at Wood River,  Illinois.   The installa-
tion was originally started up in September 1972.   Preliminary
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 operations in September and October 1972,  using gas  as  the
 reheat fuel,  indicated that the  unit was meeting the performance
 criterion of  greater  than 85 percent net S02  removal.   In October
 1972  it became evident that the  shortage of natural  gas would
 preclude its  use  as reheat fuel  for the burners.   It was, there-
 fore,  necessary to modify the burner equipment  to  fire  oil  exclu-
 sively the system was  returned to operation on  August 14, 1974.
 Mechanical and structural problems  have caused  sporadic operation
 since  then.

           Typical operating problems  at Wood  River may include
 plugging of the catalyst  bed with fly ash, catalyst  attrition
 during cleaning, and fly  ash build-up in the  final mist elim-
 inator.   There would be fewer problems with oil-fired units than
 with the  coal-fired units because less fly ash  is present in
 the former.  Reliable  precipitator  operation  seems to be par-
 ticularly  important for coal-fired  plants since heavy particulate
 loading  can cause catalyst  plugging and poisoning.  The moisture
 content  in normal flue gas  limits direct acid production to a
 yield  of  70-80 percent H2SO,,, a less desirable by-product than
 either pure acid,  sulfur, or S02  gas.

           3.4.5  Double-Alkali Process - A variation of both
 the sodium- and ammonia-based scrubbing processes is the double
 alkali process.  Here  sulfur dioxide is scrubbed with a clear
 liquor of  sodium or ammonium salts and the resulting solution
 is treated with lime or limestone to precipitate calcium salts
 for disposal and to regenerate sorbent.

          General  Motors  (G.M.)  is a leading developer of the
double-alkali process  in this country.  G.M.  is currently test-
ing a full-scale,  industrial size system at its Chevrolet-
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Cleveland Plant based on its pilot plant results achieving 90
percent S02 removal from a 4700 m3/hr (2800 cfm) stream (Ref. 9).
Combustion Equipment Associates, Inc. and Arthur D. Little, Inc.
have jointly designed and built a dual alkali prototype system
at Gulf Power Company's Scholz Station.   The system is designed
to operate at a 20 Mw full load with the boiler firing 5 percent
S coal.  Testing is scheduled for early 1975.  A good deal of
work has been done in Japan by Showa Denko and Kureha Chemical
using sodium sulfite as the absorbent and limestone as the re-
generant.  Other absorbents besides NazSOi, have been investigated:
NH..OH by EDF-Kulhmann; dilute H2SOU by Chiyoda; and an undis-
closed organic compound by Monsanto.

          Although the double-alkali processes are designed to
avoid scaling problems in the scrubber,  the possibility is not
completely eliminated because a saturated CaSO,, solution still
may be returned to the system.  This problem may be avoided by
use of a number of techniques designed to lower the dissolved
solids concentration of the regenerated scrubbing liquor.

          Although development work in this area has been intense,
the process has not been demonstrated on large, coal-fired
boilers over extended periods of operation.

          3.4,6  Other Flue Gas Cleaning Systems - A number of
additional systems are at various stages of application; some
are being offered for commercial applications and others are
in earlier stages of development.  Those being offered for
demonstration include char sorption systems by Foster-Wheeler
and Commonwealth Associates, sodium solution scrubbing systems
with electrolytic regeneration by Stone and Webster/Ionics, and
a dry sorption system by Esso Research and Engineering and
Babcock and Wilcox.
                              22

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          A number of other processes have not reached the point
 of being offered  for full-scale application but are presently
 being  studied.  North American Rockwell is developing a molten
 carbonate scrubbing system, which reacts an eutectic mixture of
 lithium, sodium,  and potassium carbonates with SO .  Testing
                                                 X
 is being performed on a 10 Mw (equivalent) pilot plant, in co-
 operation with Consolidated Edison.  The Bureau of Mines has
 investigated a sodium citrate scrubbing process that produces
 by-product sulfur.

          Ammonia scrubbing of stack gases with ammonium sulfite
 and bisulfite is being studied in field pilot-scale trials by
 EPA and TVA.  Monsanto is researching an ammonia scrubbing sys-
 tem.  Organic absorbents in aqueous solutions are also being
 studied by Monsanto.   Two systems, one with thermal regeneration,
 are said to be under development.

          A char sorption system which incorporates reducing
 gas regeneration is being developed by Westvaco with the support
 of EPA.

          U.O.P.  is working to develop a proprietary aqueous
 process which produces sulfur as a by-product.   The process is
 being studied in cooperation with Commonwealth Edison on a 20
Mw pilot plant.

          3.5  Fluidized Bed Combustion

          Several types  of fluidized bed combustion systems
are under development.   A chemically active fluidized bed which
 gasifies/desulfurizes residual oil at atmospheric pressure in
 a fluidized bed of limestone is being developed at Esso, Ltd.
 (England) with support by EPA.  Coal-fired pressurized fluidized
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bed  systems with  limestone are also under development in the
United States where EPA  is supporting work at the Westinghouse
R&D  Center, Argonne National Laboratory, and Esso Research and
Engineering.  USDI's Office of Coal Research (OCR) is supporting
a 30 Mw demonstration of an atmospheric coal-fired fluidized
bed.  The EPA work with coal in limestone beds is being conducted
on bench and pilot scale, and a number of process concepts
(pressurized, regenerable, nonregenerable) will be evaluated.
EPA has also studied the concept of using fluidized bed systems
equipped with sulfur oxide scrubbing systems for use in disposal
of high ash, high sulfur residues produced by other coal proces-
sing systems.

          Fluidized bed systems are attractive for their ability
to control both sulfur oxides and nitrogen oxides, particularly
in pressurized systems.  In addition, their capability for
burning very high ash materials makes them potentially useful
for utilizing fuel residues and low grade fuels such as oil
shales, which are becoming increasingly valuable.

          3.6  Coal Gasification (High HV Gas)

          Within the past 4 years,  a great deal of money and
energy has been directed at the development of a substitute or
synthetic natural gas (SNG) process which will prove economic
and reliable.   Viewed by many as a nostrum to the United States'
natural gas supply limitations,  the production of SNG from coal
faces a number of inherent obstacles--most having to do with
coal's lower hydrogen content in comparison to other fossil
fuels (Ref.  10).   Development efforts are underway toward
adapting commercially available low heating value (HV)  gas
systems to production of high HV gas.  The Lurgi, Koppers-Totzek
                              24

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 and McDowell-Wellman processes have been used commercially in
 Europe to produce low HV gas from coal.   In addition,  there are
 four new processes for coal  gasification to high HV that have
 advanced to or are near the  pilot stage  of development (Ref.  11,
 12).   These processes (and their developers)  are as follows:

           1.   Hygas (Institute of Gas  Technology)

           2.   Bigas (Bituminous Coal Research)

           3.   Synthane (Bureau of Mines)

           4.   C02  Acceptor (Consolidation  Coal Company)

           The  processes  listed above basically differ  in the
mechanism  of coal  gasification and  in  gasification  design,  but
they may be generalized  as high temperature  (400°C  (742°F)  to
1700°C  (3092°F)) and  high  pressure  (35-70  atm) operations.  A
high HV gas may be  obtained  following  gasification with  a
methanation  (or gas separation)  step.  However, methanation of
gasifier effluent has  yet  to be  demonstrated on a commercial
scale of the magnitude contemplated.   Conversely, a low  HV gas
may be obtained by  substituting  air for oxygen in the gasifier.
This low HV gas is  suitable as boiler  fuel or for use in combined
gas-turbine/steam-turbine  cycles  (Ref.  10).  Coal conversion to
low HV gas is discussed  in Section 3.7.  The high HV processes
are discussed below.

           3.6.1  Modified Low HV Gasification Processes  - Work
is underway to adapt  low HV systems to production of high HV
gas.  The  low HV systems can be purchased now, but they have
inherent characteristics which will limit their ultimate useful-
ness unless improvements are  made.  For example,  the Lurgi
                              25

-------
system, which has found much usage throughout the world, can
process only carefully prepared and sized noncaking coals.  In
addition, the sizes of modules which can be used are limited
and these will need to be equipped with systems for flue gas
cleanup and water pollution control.

          3.6.2  Hygas Process - Basic Hygas process features
in this design are the addition of hydrogen to the gasifier to
promote methane formation and production of the required hydrogen
by electrothermal gasification.  However, several options are
being investigated in lieu of electrothermal gasification.  Coal
is crushed, dried, and slurried in light oil before being sent
to the gasifier.  In the gasifier, one-half of the coal is
devolatized and then gasified by heating to 925-980°C (1697-
1796°F) in the presence of a hot, hydrogen-rich stream and steam.
The remaining char is conveyed to an electrothermal gasifier
where it is electrically heated in the presence of steam to form
a gas mixture of hydrogen and carbon oxides.  The gas stream is
returned to the hydrogasifier (at about 1040°C (1904°F) and
57,000 mm Hg (1130 psi)) and the remaining char is burned in a
power plant to provide the process with electrical energy and
steam (Ref. 10).

          A 68 metric ton/day (75 ton/day) pilot plant in Chicago
began operation in 1972.  The unit has experienced equipment
materials and plugging problems that are being solved as opera-
ting experience is gained.  Two additional designs are being
prepared to generate the hydrogen-rich gas required by the
process--steam/iron gasification and steam/oxygen gasification
(Ref.  11).
                              26

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           3.6.3  Bigas Process - In the Bigas process,  gasifica-
 tion of the coal feedstock occurs in two stages.   In the first
 or upper section,  about one-third of the coal is  volatilized
 and reacted with synthesis gas from the lower stage to  form a
 gas mixture and unreacted char.   After separation in a  cyclone,
 the gas mixture is purified and  converted to SNG  while  the char
 is returned to the lower stage for gasification in the  presence
 of steam and oxygen (Ref.  10).
  i
           Development  work with  this process was  completed on
 a 45 kilogram/hour (100 Ib/hr) internally fired process and
 equipment development  unit in 1971.   Since then,  construction
 has begun on a fully integrated  4.6 metric ton/hour gasification
 pilot plant at Homer City, Pennsylvania.   Initial start-up of
 the plant is planned for early 1975.

           3.6.4  Synthane Process - In the Synthane process,
 developed by the Bureau of Mines, gasification occurs in three
 stages inside the  gasifier.   Char separated from  the product
 gas is recycled to the lower part of the  gasifier and ash is
 discharged from the bottom.   Gas is sent  through  purification
 and methanation steps  to produce a pipeline quality gas.   A
 pilot plant for this process is  now under contract.

           3.6.5  C02 Acceptor Process  -  The heat  necessary for
 gasification in the C02  Acceptor Process  is supplied to the
 reacting coal by a circulating bed of  heated dolomite.   Gas
 leaving the gasifier may contain up to 20 percent methane and
 thereby eliminate  the  shift  conversion step in the methanation
 process.   This  process has been  specifically developed  for use
 with lignite.   A pilot plant now in operation at  Rapid  City,
 South Dakota processes 26 metric tons (30 tons) of lignite per
day.  After two years of operation, during which many mechanical
                              27

-------
problems were overcome, the pilot plant began producing useful
process data.  In the past year, a series of successful fully-
integrated runs have demonstrated the technical feasibility of the
process.

          3.6.6  Schedule - With supplemental supplies of
natural gas arriving from Canada and the Alaskan North Slope
toward the end of the decade, it is unlikely that significant
coal gasification to high HV gas will emerge before the 1980
to 1985 period (Ref.  13).   The technology of gasification is
generally too new to have much impact on gas prices prior to
this same period,

          3.7  Coal Gasification (Low HV Gas)

          The Lurgi,  Koppers-Totzek and McDowell-Wellman processes
have had extensive commercial use in Europe to produce a low HV
gas from coal.   All of the coal gasification steps considered
to have potential for incorporation in high HV systems are gen-
erally felt to be appropriate for improved production of low HV
gas for production of power.   Schemes for introduction of low HV
gases into modified conventional boiler systems or into combined
gas/steam cycles for power generation have only come under
investigation within the past 2 years.   Use in combined gas/
steam cycles for power generation could be feasible with only
minor advances in gas turbine technology.

          Generally,  processes which have been commercialized
for some time are relatively costly for this application since
they are operated at low pressure and throughput rates.  Efforts
have been underway to improve these operating conditions.  Most
of the developmental work to date has been with large atmospheric
pressure combustion units.
                               28

-------
          The most advanced of the high pressure processes for
low HV coal gasification is the Lurgi gas generator.  In a fixed
bed, coal is gasified with injection of air to produce a low
temperature gas which can be washed to remove ash and tar.
Hydrogen sulfide can be removed by commercially proven processes.
In Germany, cleaned gas is then used in a steam-turbine/gas -
turbine combined cycle power plant.

          Of the high HV gasification processes described pre-
viously, the Bureau of Mines' Synthane process and the two-stage
Bigas process of Bituminous Coal Research should be capable of
substituting air for oxygen to produce low HV gas without major
modifications.

          It appears doubtful that endeavors to apply current
low HV technology to high pressure, high throughput coal gas-
ification will be economically significant before 1980.

          3.8  Coal Liquefaction

          In the past 2 years, coal liquefaction research has
shifted in emphasis from processes aimed at the formation of
a petroleum-type product from coal gasifier effluent to  those
producing a low sulfur, low ash liquid fuel suitable for boiler
firing (Ref.  13).   Several processes are currently under develop-
ment with sponsorship from the OCR (USDI).   One of these
processes which has advanced to the pilot plant stage is dis-
cussed here.

          The coal liquefaction pilot plant of OCR that  is
currently in operation involves the COED (char-oil energy
development)  process developed by FMC Corporation.  The  COED
                              29

-------
process  involves coal pyrolysis to convert the feedstock into
more valuable and pollutant-free products such as synthane,
crude oil, gas and char.  In the process, coal is volatilized
in a series of fluidized bed reactors where it is reduced to
its component parts.  Gas from the process can be sold as fuel
gas or converted to pipeline gas or hydrogen with the applica-
tion of  additional technology.  Oil from pyrolysis is filtered
to remove solids and hydrotreated at high temperature and pres-
sure to  remove sulfur, nitrogen, and oxygen.   The product is a
25° API  synthetic crude oil.  Residual char can be used as
power plant fuel, gasified to produce fuel gas, or processed to
generate hydrogen (Ref.  11).

          At this state of development, it is difficult to pre-
dict the size of the market that coal liquefaction products
might attract in the next 10 years.   On the basis of their
infantile technology, however,  it seems unlikely that these
processes will have a major effect on the low sulfur fuel oil
supply/demand balance before 1980 or 1985.

4.0       Economics of S02 Control Alternatives

          An economic comparison of most of the S02  control
alternatives discussed in Section 3.0 is presented in this
section.   The estimates,  based on best available information,
include capital and operating costs  in consistent units.   Cost
analyses  of emerging technologies are hazardous because of
their evolutionary nature:   estimates of capital and operating
costs for processes only at the bench-scale or pilot phase  of
development may be speculation.
                                30

-------
          Future costs for naturally occurring clean fuels are
perhaps the most difficult to predict due to the uncertainty of
the supply and the market's response to diverse factors  (e.g.,
stack gas desulfurization and import limitations).  Fuel costs
for gas, oil, and coal based on August 1974  data  (Ref.  14)
are summarized in Table 1-5.

          Because of past regulatory practices, natural  gas is
currently low in cost despite the desirability of  this fuel.
The natural gas costs reported in Table 1-5 were based on a
survey of over 500 utility contracts.  This survey showed that
unregulated intrastate gas was being sold for as much as 18
mills/Kwh while interstate regulated gas averaged  5 mills/Kwh.
Since the majority of natural gas used by utilities is inter-
state, it is anticipated that if natural gas were  deregulated
prices would rise dramatically.

          As shown in Table 1-5, both naturally occurring and
desulfurized residual and distillate fuel oil prices were higher
than other fossil fuels regardless of sulfur content.  Unlike
natural gas, there was not a wide price range reported for fuel
oil in the survey.  Fuel oil containing approximately 1  per-
cent sulfur was reported to be selling for approximately 18
mills/Kwh while 0.3 percent sulfur fuel oil was selling  for 20
mills/Kwh.

          Coal costs in Table 1-5 range from 3.1 to 9.0 mills/
Kwh depending on the sulfur content and the locality.  Coal
prices F.O.B.  the plant are for Western coal used by Western
utilities and Eastern coal used by Eastern utilities.  It should
be noted that most Western plants are minemouth plants and that
transportation costs for Western low sulfur coal could be as
much as $0.51/metric ton-100 kilometers (about $0.75/ton-100
                              31

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                                      Table 1-5   ECONOMIC ESTIMATES FOR S02 CONTROL ALTERNATIVES8

                                                               (1974 DOLLARS)
SC>2 Control
Alternative
Low Sulfur Fossil Fuels
Gas

Oil
Western Coalb

Eastern Coalb
Coal Cleaning
Physical

Chemical (Pyritlc S Removal)


U> Desulfurlzation of Oil
ho 1 wt % Sulfur Oil
0.3 wt % Sulfur Oil
Flue Gas Desulfurlzation Process
Double Alkali
Lime Scrubbing
Limestone Scrubbing
MgO (to H2SO&)
Wellman- Lord (to H.SOO
Wellman- Lord ftn ^
Cat-Ox
Fluidized 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

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.
Limited low-S avail.

Limited: only ~ 257. 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/Kwh

4.0-6.0

18.0-20.0
4.0-6.0

4.5-9.0

3,1,6.7C

3.1-6.7C



15. Od
15. Od

3.1-6.7C
3.1-6.7C
3.1-6.7C
3.1-6.7C
3.1-6.7C
3.1-6.7C
3.1-6.7C
3.U6.7


3.1-6.7

3.1-6.7

3.1-6.7

Effective Fuel
Costs (Fuel
Annualized Cost +
Control Costs, Annualized Con-
Capital Costs mills/Kwh trol Costs)

N/A 	

N/A
N/A

N/A

$10/Kw 0.8-1.5

$26 /Kw 1.55



N/A
N/A

$61/Kw 3.55
$45/Kw 2.90
$50/Kw 2.86
S53/Kw 3.07
$60/Kw 3.67
$61/Kw 3.80
$85/Kw 3.44
$308/Kwf 0.3- 1.78


$72-$109/Kw

$75-$125/Kw

$60-$90/Kw


4.0-6.0

18.0-20.0
4.0-6.0

4.5-9.0

3.9-8.2

4.7-8.3



18.0
20.0

6.7-10.3
6.0-9.6
6.0-9.6
6.2-9.8
6.8-10.4
6.9-10.5
6.5-10.1
3.4-8.4


8.3-12.8

12+

6.5-9.6

••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.
•jCoal cost is for high sulfur  (3.0-4.01 S)  Eastern
"Oil cost Is for 3.5-4 OX  S crude  oil.
fPressurized fluid bed boiler  combined  cycle,  once
-Includes power generation equipment.
"Control considered inherent In  the boiler
coal.

through system, coal

-------
miles).  For a typical 1600 kilometer (1000 mile) delivery,
the F.O.B. plant cost for Western low sulfur coal delivered in
the West, the cost would be 8-10 mills/Kwh.

          Estimates of economics, availability for application,
and applicability to the utility industry of current S02 con-
trol technologies are also summarized in Table 1-5.  While the
individual values used in this comparison may not be absolute,
the relative costs are considered representative.  Each of
these alternatives is discussed below.

          Costs for physical coal cleaning, a currently avail-
able technology, were based on reports of U. S. Bureau of Mines
(Ref. 15), Bituminous Coal Research (Ref. 16), and Paul Weir
(Ref. 17).  Costs for chemical coal cleaning were estimated by
TRW (Ref. 18) based on a recently completed bench-scale study
for EPA.  Estimated capital and total annualized operating
costs were $26/Kw and 1.50 mills/Kwh for a 225 Mw plant opera-
ting at about 75 percent load factor.   Capital costs for chemical
cleaning were found to decrease with decreasing load factor.

          Capital and operating expenses for flue gas desul-
furization systems are somewhat easier to estimate since cost
breakdowns are available from actual installations.  Care must
be taken, however,  when quoting capital and operating costs to
specify the basis on which they were made.   This is true since
costs for flue gas desulfurization are sensitive to size and
age of the boiler,  flue gas scrubbing rate, sulfur content of
inlet gas, load factor,  waste disposal costs,  and by-product
credits, among other factors.

          McGlamery (Ref.  19)  has prepared comparative process
costs for seven of the eight flue gas desulfurization processes
                               33

-------
discussed in preceding Section 3.0.   (Cost estimates are not
yet available for the B&W-Esso process.)  These costs included
in Table 1-5 are for a new installation of the processes at a
500 Mw generating station operating an average of 4250 hr/yr
over a 30 year life and burning 3.5 percent sulfur coal.  Waste
disposal costs were taken to be $3/metric ton wet sludge.  A
$25/metric ton by-product sulfur credit and an $8/metric ton
by-product sulfuric acid credit are allowed.

          Annualized costs for flue gas desulfurization processes
are estimated between 3 and 4 mills/Kwh, with a mean near 3.5
mills/Kwh.  These costs can be considered typical for comparison
with other S02 control technologies.

          Fluidized bed combustion of coal will apply only to
new units.  Westinghouse (Ref. 20) estimated capital and an-
nualized operating costs at $308/Kw and 7.67 mills/Kwh (excluding
fuel costs), respectively, for a coal-fired, 635 Mw pressurized,
once-through, fluid bed boiler, combined cycle.  Load factor was
70 percent and no credit for sulfur was included.  Since these
costs are for a new unit they take into account equipment costs
common to conventional units.  As such, they cannot be compared
directly with other control alternatives.  However, the capital
cost approximates that for a conventional boiler plus S02
control by FGD.  On this basis, annualized control costs have
been estimated to be zero-1.7 mills/Kwh.

          Coal gasification technology presents an alternative
which may, in the long term,  become economically competitive
with flue gas cleaning.   Production of low HV gas by the Lurgi
process would require capital investments of about $180 to $190
million for a 7 million cubic meter (250 million cubic foot)
per day plant (Ref.  21).   Operating costs for this process are
                               34

-------
particularly high.  The selling price of SNG from a Western
low sulfur semibituminous coal is expected to be approximately
12.5 mills/Kwh  (Ref. 11, 22).  Lower costs are expected for
advanced low HV gasification processes using higher temperatures
and pressure.

          High HV gasification processes producing pipeline
quality gas are expected to be even more expensive than low HV
gasification schemes.  Capital investment estimates for the
four high HV gasification processes discussed in Section 3.6
vary from $200 to $230 million for a 7 million cubic meter (250
million cubic foot) per day facility.  The cost of pipeline
gas from these processes is expected to be more than 12 mills/
Kwh (Ref. 23).

          Gage (Ref. 24) has discussed the status of various
coal liquefaction processes and indicated that the technology
was in an early state of development.  It was estimated that
capital costs would be in the $  60-90 /Kw range and energy cost
would be in the 6.5-9.5 mills/Kwh range.   M.  W. Kellogg has
reported operating costs of 10.0-13.0 mills/Kwh for an SRC
process on an existing 500 Mw boiler (Ref.  22).

5.0       Economic Comparison of Regenerable Versus Nonregenerable
          FGD Processes

          Figure 1-1 is presented to illustrate the bounds on
the economic comparison of regenerable FGD with throwaway FGD.
The figures show lime/limestone process costs as a function of
sludge disposal costs relative to regenerable processes.

          Sludge disposal methods,  for which costs are estimated,
are unlined ponding, lined ponding,  chemical treatment (fixation)
                             35

-------
   z
   o
         4.0
   
-------
and landfilling, and fixation plus lined landfill.  The ap-
proximate ranges of sludge disposal costs included in the
figure generally indicate an apparent minimum representing ideal
circumstances, and an extension to the extreme right reflecting
a broad range and our lack of knowledge regarding a reasonable
upper limit.

          The cases considered for comparison are MgO with the
sale of acid, Cat-Ox with the sale of acid,  and sodium systems
with the three possibilities of the sale of acid, the sale of
sulfur, or the storage of sulfur,

          The process cost lines represent the center lines
of bands 0.4 mills/Kwh wide reflecting a tolerance of approx-
imately ±10% to account for plant to plant variability (even
with a fixed basis) and lack of estimate precision.   The esti-
mates were based on the following assumptions:

          1.  Cost estimates are made on the basis
              of a 500 Mw new plant burning  3.5% S
              coal with an average load factor of
              4250 hr/yr over a 30 year life.

          2.  Process costs are not for a first of
              a kind installation requiring  exten-
              sive R&D,  debugging, or reconstruction
              expenditures.   Such expenses as  first
              year operation,  all R&D and other
              expenses frequently included in
              utility capital cost estimates,  are
              not included.
                              37

-------
          3.  Sludge and ash are produced at the
              rates given in Table 1-8, Case 5.

          4.  For a given process, it is 0.15
              mills/Kwh more expensive to produce
              elemental sulfur than sulfuric acid.
              This cost would be slightly higher
              for Mag-Ox than for Wellman-Lord.

          5.  Both acid and sulfur would sell for
              $25/ton sulfur.

          6.  It costs $2/dry ton or 0.02 mills/
              Kwh to store elemental sulfur.

          Figure 1-1 presents the case in which the utility's
ash collection and disposal system is separate from the lime/
limestone scrubbing and sludge disposal system.  If ash will
be disposed of separately or if no ash is required for fixation,
this figure presents the lower bounds on lime/limestone process
costs.  The following observations can be made:

          1.  Assuming the existence of a market
              for the products produced by regen-
              erable systems, lime scrubbing is
              less expensive than the regenerable
              systems considered below sludge dis-
              posal costs of about $4/wet ton.  Lime
              scrubbing is competitive with the
              regenerable systems up to disposal
              costs of about $10/wet ton.  In the
              case of storage of sulfur from a sodium
              system, lime scrubbing is still
                              38

-------
              competitive at costs greater than
              $11 per ton.  Lime scrubbing is
              more expensive than MgO  (sell acid)
              at any expected fixation cost.

          2.  Assuming the existence of a market
              for by-products, limestone scrubbing
              is less expensive than the regener-
              able systems considered below a dis-
              posal cost of about $4/wet ton.
              Limestone scrubbing is competitive
              with the regenerable systems up to
              disposal costs of about $7/wet ton.
              Limestone scrubbing with disposal
              costs greater than $7/wet ton is
              competitive with the sodium process
              in which sulfur is stored.  Limestone
              scrubbing is more expensive than MgO
              (sell acid) at any expected fixation
              costs.

          It should be noted that the costs in Figure 1-1
are presented primarily for general comparisons and for demon-
strating the economic considerations impacting the choice
between regenerable and nonregenerable FGD.  For specific in-
stallations, sludge disposal cost crossovers could vary
considerably.

B.         POTENTIAL DEMAND FOR LIME/LIMESTONE SCRUBBING

1.0       Introduction

          Of the leading commercially available processes for
controlling sulfur emissions from fossil fuel-fired generating

                              39

-------
 stations,  lime/limestone  scrubbing  is  the  only  one which  produces
 a throwaway sludge.   The  potential  demand  for lime/limestone
 scrubbing  must  be  assessed  in  order to  determine  the  quantity
 of throwaway sludge  that  will  be produced.

           At present,  the installation  of  flue  gas desulfuriza-
 tion  systems is  demand-limited due  to a number  of factors  such
 as  lack of confidence  in  the ability of the vendors to perform
 as  promised,  anticipation that regulations may  be altered  in
 the near future, potential  difficulties in raising capital and
 obtaining  rate  increases  to cover expenses for  pollution abate-
 ment, and  the lack of  suitably trained  personnel  in the utility
 industry to  evaluate and  operate scrubber systems.  These
 factors are  being altered with time, and familiarity with  the
 technology is increasing.  Questions of confidence in system
 reliability  will be erased with time as the utilities observe
 smooth operation from  existing systems.  With increased demand
 pressure,  the installation of  scrubber  systems will probably
 become supply-limited  due to such factors as availability of
 capital, availability  of  engineering/design services,  demand
 and supply of critical labor categories, availability of major
 equipment  suppliers,  effect of down time on reserve generating
 capacity,  and vendor capability.   These supply limiting factors
 result from  the evolutionary stage of development of this
 technology.  The demand and supply limiting factors  mentioned
 above have been the subject of many reports prepared by and
 for the EPA  (Ref. 23, 25,  26),  and an in-depth study of these
 factors is beyond the scope of this report.

          The trends  in the degree of flue gas desulfurization
system utilization and the types  of systems which are  presently
favored by the utilities  can be ascertained by analyzing  present
and planned flue gas  desulfurization systems in  the  United States.
                              40

-------
In Table 1-6 the full-size scrubber systems planned or operating
in the United States are listed according to process type with
the plant size,  start-up date,  fuel, and S02 removal efficiency
given for each plant.   Based on the data in this table, the
following observations can be made:

          1.   Presently, 43 flue gas desulfurization
              systems  are planned or in operation;
              29 are lime or limestone scrubbing units;
              four are sodium based (two of these are
              the Wellman-Lord process);  four are
              magnesium oxide systems; one is a dry
              system (Cat-Ox);  and five are fly ash
              scrubbing systems with provisions for
              conversion to lime/limestone or sodium-
              based scrubbing.

          2.   The majority of the systems are in-
              stalled  on coal-fired units; only three
              of the 43 systems are on oil-fired
              units.

          3.   The total megawatts represented by
              these units is about 24,000.

          4.   The majority of the systems (by number)
              are retrofitted onto existing boiler
              facilities.   The  majority of capacity,
              however,  is on new plants.

          5.   Presently,  about  9,000 Mw of control
              capability is scheduled to  be installed
              as of 1975.
                              41

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Table 1-6.  PLANNED AND OPERATING FULL SIZE FLUE GAS DESULFURIZATION
                  FACILITIES IN THE UNITED STATES3


1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
j> 11.
tsJ 12.

13.

14.
15.
16.
17.
18.
19.
20.

21.
22.
23.
24.
25.
26. .
27.
28.
29.
Utility Company/Plant /New or Retro
Lime/Limestone Scrubbing
Kansas Power & Light /Lawrence No. 4/Retro
Kansas Power & Light/Lawrence No. 5 /New
Commonwealth Edison/Will County No. I/Retro
City of Key West/Stock Island/New
Kansas City Power & Light/ Hawthorne No. 3/Retro
Kansas City Power & Light/ Hawthorne No. 4/Retro
Louisville Gas & Electric/Paddy's Run No. 6/Retro
Kansas City Power & Light/LaCygne/New
Detroit Edison/St. Clnir No. 6/Rctro
Arizona Public Service/Cholla/Retro
Duquesne Light Co. /Phillips/Retro
Southern California Edison & other Southwestern
Utilities/Mohave No. I/Retro
Southern California Edison & other Southwestern
Utilities/Mohave No. 2/Retro
Ohio Edison & others/Bruce Mansfield/New
Montana Power/Colstrip No. 1 & 2 /New
Tennessee Valley Authority/Widow's Creek No. 8/Retro
Louisville Gas & Electric/Cane Run No. 4
Kentucky Utilities/Green River No. 1, 2, 3
Northern States Power/Sherburne County No . 1 S 2/New
Southern California Edison & other Southwestern
Utilities/Navajo No. 1, 2 & 3/New
Public Service oE Indiana/Gibson/New
Potomac Electric & Power/Dickerson No. 4 6 5/New
Columbus & Southern Oil Electric/Conesville
Arizona Public Service/Four Corners No. 1-5/Retro
Southern Public Service/Harrington No. 1
Springfield Missouri/Southwest No. 1
Texas Utilities/Martin Lake No. 1-4/New
Louisville Gas & Electric/Mill Creek No. 3
Kansas Power & Light/Jeffrey No. 1-4
Plant Size, Mw

125
430
163
37
130
130
70
820
170
115
100
160

160

1650
720
550
178
64
1360
2250

650
1700
750
1180
343
200
3172
425
2800
Start-Up

December 1968
November 1971
February 1972
February 1973
November 1972
August 1972
April 1973
June 1973
December 1973
October 1973
October 1973
December 1973

1974

1975
1975
1975
1975
1975
1976, 1977
1976, 1977

1976
1976, 1977
1976
1976, 1977
1976
1976
1976-1979
1977
1979
Fuel

3.5% S Coal
3.5% S Coal
3.5% S Coal
2.75% S Oil
3.5% S Coal
3.5% S Coal
3.5% S Coal
5.25% S Coal
3.7% S Coal
0.4-1% S Coal
2.0% S Coal
0.5% S Coal

0.5% S Coal

4.3% S Coal
0.8% S Coal
3.7% S Coal


0.8%-1.2% S Coal
0.3%-0.8% S Coal

1.5% S Coal
2.0% S Coal
Uncertain
0.75% S Coal





S02 Rpmoval Efficiency. %

70-75
70-75
75-85
85 (expected)
70
70
80+
80 (expected)
82
Uncertain
80
Uncertain

Uncertain

90+
Uncertain
80


50
Uncertain

80
Uncertain
90
Uncertain






-------
                Table  1-6  (Continued)-  PLANNED AND OPERATING FULL  SIZE FLUE GAS DESULFURIZATION FACILITIES IN THE UNITED STATES3
CO


30.
31.
32.

33.

34.
35.
36.
37.
Utility Company/Plant/New or Retro
Sodium Base Scrubbing
Nevada Power Co. /Reid Gardner No. 1 &2 Retrob
Northern Indiana Public Service Co./D.H. Mitchell
No. 11/Retro (Wellman-Lord)
Public Service Co. of New Mexico/San Juan No. 1
& 2 Retro (Wellman-Lord)
Nevada Power Co. /Gardner No. 3
Magnesium Oxide Scrubbing
Boston Edison/Mystic Station No. 6/Retro
Philadelphia Electric Co. /Eddystone No. I/Retro
Potomac Electric & Power/Dickerson No. 3/Retro
Potomac Electric & Power/Chalk Point No. 3 & A/New
Plant Size, Ma

250
115
715

125

150
120
100
1260
Start-Up

1973
1975
1977

1975

April 1972
1974
1974
1975, 1976
Fuel

0.5-1% S Coal
3.5% S Coal
0.8% S Coal



2.5% S Oil
2.5% S Coal
3.0% S Coal
Oil
SO- Removal Efficiency, %

83-92 (50 ..

nnm outlet)
90 (200 ppm outlet)
Uncertain



90+
Uncertain
90
Uncertain








     38.
Cat-Ox
Illinois  Power/Wood River/Retro
                                                                      100
                                                                                      September  1972
                                                                                                3.25% S Coal
             *Ref.  27
             ^Once-through sodium scrubbing
             'Provisions for conversion to lime/limestone or sodium-base scrubbing
                                                                                                                       85
Fly Ash Scrubbing0
39.
40.
41.
42.
43.
Public
Public
Public
Public
Public
Service of
Service of
Service of
Service of
Service of
Colorado/Valmont No. 5/Retro
Colorado/Cherokee
Colorado/Cherokee
Colorado/Cherokee
Colorado/Arapahoe
No.
No.
No.
No.
I/Retro
3/Retro
4/Retro
4/Retro
100
125
150
350
100
October 1971
June 1973
October 1972
August 1974
September 1973
0.3%
0.5%
0.5%
0.5%
0.8%
S
S
S
S
S
Coal
Coal
Coal
Coal
Coal
40
35
20 (expected)
20+
35

-------
          6.  The average fuel fired contained 3
              percent S.

          7.  The average S02 removal efficiency is
              roughly 80 percent.

          The installed capacity for flue gas desulfurization
systems would appear to be no more than 10,000 Mw in 1975 since
2 to 3 years design and construction time for a system would
require that essentially all systems that will be operational
in 1975 be on order in 1973.  The systems presently contracted
to be installed by 1979 would bring the total megawatts con-
trolled up to 24,000.   This amount could be increased sub-
stantially if the institutional barriers presently causing
installation of systems to be demand-limited were removed and
the utilities were to make decisions to install such systems
in the next few months.

2 0       Availability of Alternatives

          During the period between now and 1980, a number of
SOX control technologies will be available to the utility industry.
These alternatives will include lime/limestone scrubbing, other
flue gas desulfurization technology, fuel cleaning, and burning
naturally clean fuels.  The utilities will probably continue
the current pattern of selecting wet scrubbing systems, with
the majority of orders for lime/limestone throwaway systems.
There will probably be a significant increase in the number of
orders for regenerative processes above the near term trends
as market studies of various geographical areas are completed
and use of sulfur increases.
                              44

-------
          Processes such as liquefaction and gasification of
coal will have insignificant applicability in the utility
industry between now and 1980.   Even the energy projection pre-
pared by USDI (Ref. 1), the developers of most of the liquefaction/
gasification processes, indicates that energy from these sources
will provide less than 0.5 percent of the total United States
energy demand in 1980.

          Burning clean fuels (natural gas, low-sulfur oil, and
low-sulfur coal) as an alternative to installing scrubbing
systems will enjoy limited applicability in the utility industry.
It is anticipated that greater than half the coal generating
capacity and greater than one-third the oil-fired generating
capacity in 1980 will have to be produced using high sulfur
fuel.  Switching fuels from coal or oil to natural gas, of course,
will not be feasible.

          Figure 1-2 shows the location of coal-fired generating
stations over 200 Mw in the United States.  It is obvious from
the map that the vast majority of the coal-fired generating
capacity is located in the Eastern half of the Nation with the
greatest concentration in the Northeast and East Central regions.

          The majority of plants are located in regions rich in
high-sulfur (3-4 percent) coal and far away from the major low-
sulfur coal deposits in the West (mainly Wyoming and Montana).
Transportation costs make the low-sulfur Western coal appear
economically unattractive in many areas of the East, especially
when the complexities of burning Western coal in some Eastern
boilers not designed for Western coal are considered.

          The East Central, West Central, South Central and
Southeast sections of the country use tremendous amounts of
                             45

-------
Figure 1-2.   Coal-Firec! Generating Stations Over 200 Mw in the United States  (1971)

-------
sulfuric acid in fertilizer production.  A market survey recently
completed by TVA concluded that abatement acid might penetrate
the market with the proper price incentive by replacing sulfuric
acid produced from purchased sulfur (Ref. 28).  In view of this
fact significant numbers of regenerable systems may be installed
in these areas.

3 0       Projected FGD Meed

          Present uncertainties about alterations to existing
compliance regulations and the time frames allowed for compliance
with the 1970 Clean Air Act and state implementation plans should
be resolved by legislation currently before Congress.  While
the time frame for compliance with NAAQS may change from the
present 1975-1977 period, every effort will be made to meet the
primary standards before 1980.   No relaxation of the EPA standards
for new plants is anticipated.

          There are about 970 fossil fuel steam-electric plants
operating in the United States, with a total generating capacity
of about 302,000 megawatts (1972 figures).  Of this capacity,
roughly 55 percent or 166,000 megawatts are coal-fired and 17
percent or 51,000 megawatts are oil-fired (Ref. 29).  Many of
the oil- and coal-fired plants were already in compliance with
applicable sulfur oxide emission limitations before current
state implementation plans were developed.  These plants had
either undertaken control efforts, such as purchasing low-sulfur
fuels,  or were in areas where the sulfur dioxide ambient levels
were not severe enough to warrant stringent emission limitations.
Since the time when the implementation plans were approved, a
number of additional plants have come or are coming into
compliance by converting to fuels having lower sulfur contents
and in some cases by installing FGD systems.

-------
          For  the remaining noncomplying plants, EPA, in the
January  1974 National Power Plant Hearings Report  (Ref. 30),
attempted to determine the amount of flue gas desulfurization
that will be needed nationally to assure timely attainment and
maintenance of primary ambient air quality standards.  This
analysis was performed by looking at the need through 1980 for
FGD on new and existing coal-fired plants and for oil-fired
plants expected to switch to coal.  Due to the uncertainties
in the oil supply situation, it was not possible to analyze the
need to retrofit existing oil-fired plants with FGD systems.

          To quantify the need for FGD for existing coal-fired
plants, EPA used diffusion modeling techniques to determine how
many of these  plants have an impact on attainment of the primary
standards.  The projected growth of United States coal-fired
capacity from  the 1972 level of 166,000 megawatts to 209,000
megawatts in 1975 (EPA estimate) was taken into account.  Of
this 209,000 megawatts,  some 123,000 megawatts are not expected
to need any emission reductions to achieve primary standards;
23,000 megawatts are expected to need moderate reductions through
such techniques as washing currently used coal or blending this
coal with low-sulfur coal; and 63,000 megawatts are expected to
need substantial reductions either through the use of low-sulfur
coal or FGD.

          EPA estimated that an average of 24,000 megawatts of
new fossil fuel capacity will come into operation each year
after 1975.   Of this,  about 14,500 megawatts will be coal-fired.
Since many of these plants will not be able to comply with state
emission requirements  or federal new source performance standards
through the use of low-sulfur coal,  they will greatly increase
the need for FGD after 1975.
                              48

-------
          As indicated above, a number of plants now using
oil are expected to switch to coal because of oil shortages.
Most of these plants will need to apply FGD systems in order
to ensure attainment and maintenance of primary standards.  The
estimated additional scrubber needs for plants switching from
oil to coal were added by EPA to the needs calculated for exist-
ing and new coal-fired plants.

          Some utilities will be able to obtain low-sulfur
coal for their plants.  New supplies of low-sulfur coal will
not be significant between now and 1975; however, limited
supplies will be available after that time.  By distributing
reserves and redistributing current supplies of low-sulfur coal
to the areas where they are most needed to attain air quality
standards, current and projected supplies could significantly
reduce FGD requirements after 1975.  For this reason,  estimated
new low-sulfur coal supplies were taken into account in the
EPA analysis (Ref.  30).

          The results of the analysis are displayed in Figure
1-3.   The curves in the figure show the maximum and minimum
estimated FGD needs of those coal-fired power plants that need
control for attainment of primary ambient air quality standards
and attainment of EPA's new source performance standards.  These
curves include growth in coal-fired capacity from erection of
new plants and expansion of existing plants, estimates of plants
switching from oil to coal, the increase in supplies of low-
sulfur utility coal,  and the extent to which coal will be re-
distributed in response to SOX emission limitations.   Inherent
in this analysis is the assumption that power plants having an
impact on primary standards will have priority in the distribution
of low-sulfur fuels and FGD systems.
                              49

-------
   125
   100
m
u
4-J
cd
00

-------
          Although it is difficult to precisely determine the
impact of the previously cited factors,  especially the increased
supply and redistribution of low-sulfur coal,  the middle curve
in Figure 1-3 represents the most likely demand for FGD systems.
As indicated by this curve, the cumulative need for FGD is
about 66,000 megawatts by the end of 1975, 73,000 megawatts by
the end of 1977, and 90,000 megawatts by the end of 1980.

          It is important to note that there will be additional
demands for FGD systems which were not included in the EPA
analysis.  For example, there will probably be an increasing
demand for these systems to control many industrial boilers.
In addition, the demand by oil-fired plants was not included
in the analysis (Ref. 30).

4 0       Projected FGD Need Versus Vendor Capacity

          In the January 1974 National Power Plant Hearings
Report (Ref. 30),  EPA also projected the capabilities of vendors
to supply FGD systems between now and 1980.  Two predictions of
overall vendor capacity were discussed at the hearing:  the
Sulfur Oxide Control Technology Assessment Panel (SOCTAP) Final
Report on Projected Utilization of Stack Gas Cleaning Systems
by Steam-Electric Plants (Ref. 23) and the Industrial Gas Clean-
ing Institute (IGCI) survey and analysis (Ref.  30).  In addition,
some individual vendors discussed their capacity for future
installation of scrubbers.

          SOCTAP evaluated 15 sulfur oxide control system
vendors and projected that three or four could expand rapidly
and that another three or four could expand at a slower rate.
The remaining seven to nine vendors were considered to have
unproven abilities and the panel felt that they would not play
                               51

-------
 an important  role  until  the  late  1970's.   SOCTAP  also predicted
 that  some new vendors would  enter the market.   SOCTAP did use
 two "choke  points" in their  projections:   one,  the ability of
 the vendors to market their  systems; and  two,  the ability of
 vendors  to  bring systems on-line  smoothly while continuing to
 take  on  new projects.  The potential for  delays due  to shortages
 in critical materials and engineering and skilled construction
 manpower was  considered  in their  projections  (Ref. 23).

          The  IGCI  conducted a survey of  24 vendors  (including
 nonmembers), asking for  an assessment of  each  company's uncon-
 strained capacity  to provide commercial FGD systems.  The IGCI
 analysis essentially assumed that  each vendor  polled would
 provide  100 percent of predicted  capacity.  This assumption may
 hold  in  the 1978-1980 period as more vendors gain experience
 and the  most promising systems are licensed, but it is question-
 able  for the 1974-1977 period because few vendors have proven
 capabilities to supply scrubbing  systems.  In  addition, IGCI
 stated that possible material and  labor shortages were not con-
 sidered  in  their estimates (Ref.   30).

          Figure 1-4 shows the cumulative need and cumulative
 vendor capacity estimates made by SOCTAP and by IGCI in megawatts
 of installed capacity versus time.  Also shown is the curve
which the EPA hearing panel felt best estimates the ability of
vendors to install FGD systems.

          Because orders must be placed soon for scrubbers to
be installed in 1976-1977,  vendor capacity through that period
is largely limited by existing experience and capability of
vendors.   For this reason,  the panel felt that actual experience
during this period will likely follow the more conservative
SOCTAP estimate.   Capacity in the later 1970's, however,  will
                              52

-------
          125
          100
Ul
       o
       n
       O
       o
       o
          75
       o  50'
          25-
                                                     INCLUDES  NEW  AND  EXISTING  COAL-FIRED  PLANTS

                                                     REQUIRING  CONTROLS  TO ACHIEVE PRIMARY STANDARDS

                                                     OR  NEW  SOURCE  PERFORMANCE  STANDARDS
                       76
77
78
                                                         79


                                                    Time, Years
                                  80
                                   81
                         Figure 1-4.   Cumulative  Need and Vendor Capacity.

-------
 depend on the extent to which additional vendors gain experience
 and the extent to which all vendors increase their capacities.
 This increase will depend largely upon the market the vendors
 envision.  Assuming that states and EPA push ahead vigorously
 with sulfur oxide compliance requirements, the panel felt that
 actual experience during the later 1970's will most likely
 approach the IGCI estimates (Ref. 30).

          Figure 1-4 also shows EPA's best estimate of FGD needs
 (see Figure 1-3) for existing coal-fired power plants impacting
 primary standards and for new coal-fired plants.  On the basis
 of this estimate, it is clear that the timetables of many state
 implementation plans (compliance by mid-1975) will not be met.
 However, it is also clear that the vendor supply capability
 should be able to meet the demand for FGD systems by 1980.

          In conclusion, during the 1974-1980 period,  electric
 utilities will probably continue the current pattern in select-
 ing wet scrubbing systems.   The majority of orders will probably
 continue to be for lime/limestone scrubbing systems producing a
 throwaway sludge (Ref.  24).   The balance of orders will be for
 regenerative systems,  based on magnesium,  sodium, and other
 compounds producing sulfur and sulfuric acid as by-products.
The probable ratio of throwaway processes  to regenerable processes
 indicated by current ordering trends is 3:1.   It is felt that
while the use of regenerable systems is expected to expand during
 the mid to latter part of the decade,  the  ratio of 3:1 will
probably represent the cumulative population of systems in
existence in 1980.   Using the EPA estimate of FGD need of 90,000
Mw and this ratio results in 67,500 Mw projected to be controlled
by lime/limestone scrubbing in 1980.   However,  since the EPA
estimates exclude industrial boilers and oil-fired utility
boilers, the lime/limestone demand alone  could approach 90,000 Mw.
                               54

-------
C.        QUANTIFICATION OF THE PROBLEM AND COMPARISON WITH
          ANALOGOUS ENVIRONMENTAL PROBLEMS

          One of the major problems inherent in any flue gas
desulfurization system is the necessity to dispose of or utilize
large quantities of sulfur removed from the flue gas.  The sul-
fur compounds produced by flue gas desulfurization systems fall
into two general categories:  throwaway or salable products.
Lime/limestone and double alkali scrubbing systems generate
throwaway sludge products with little commercial value projected
at the present time.  Limestone scrubbing processes ordinarily
produce sludges containing CaS03-%H20, CaSO,,-2H20, and CaC03;
lime sludges may also contain unreacted lime.  For coal-fired
installations where efficient particulate removal is not in-
stalled upstream of the wet lime/limestone absorber, such sludges
can contain large quantities of coal ash.  Even when efficient
particulate collection is installed upstream of the scrubber,
the disposal sludge may contain large quantities of ash.

          A power plant SO2 scrubbing system can be designed
with the alternative of collecting fly ash simultaneously with
the flue gas scrubbing operation or of collecting fly ash up-
stream of the scrubbing operation by precipitators and/or
mechanical collectors.   Additionally, the fly ash can be dis-
posed of with the sludge or independently of it; and, in some
cases,  it can be used as an absorbent in the scrubber.   The
design decisions affect capital,  operating and maintenance costs
and could conceivably affect the operation of both the scrubber
and boiler as well as disposal alternatives.

          In the case of a retrofit scrubbing system, the pre-
existence of a particulate control system may determine the
collection decision but not necessarily the disposal decision.
                              55

-------
 If a particulate  collection  system does  not  preexist,  the
 installation of an  S02  scrubbing  system  appears  to be  an in-
 expensive  means of  controlling particulate effluent  at little
 additional cost.

           In the  case of  a new plant,  a  decision to  design
 without mechanical  collectors and electrostatic  precipitators
 will initially save their entire  cost  and would  generally require
 little design change in the  scrubbing  equipment  except for the
 differential required to  handle a larger quantity of solids.
 Dependent  on system design,  the abrasive nature  of fly ash could
 require additional  replacement of scrubber system components
 incurring  capital costs which would reduce the savings  in initial
 capital expenditures.   The difference  in operational costs
 between the  two methods of fly ash collection does not  appear
 to be a primary consideration.  These  costs  are  highly  dependent
 on the logistics of handling and  disposal.   However, maintenance
 costs for  scrubber  collected fly  ash systems could be higher as
 a result of  repair  or replacement of hardware subjected to fly
 ash  erosion.  Unless properly designed,  a base load  unit without
 a separate particulate  control system  could  find their  compliance
 with particulate emission standards compromised  during  scrubber
 system outages.  While variances  for SOa emissions may  be granted
 during these periods, it  is not known whether, or to what extent,
 variances  for particulate emissions would be granted.   Some
 data suggest  that a  single scrubber can  control  S02  as  well as
 particulates, that  high alkaline ash may be  used as  a  sorbent
 for  S02,  and  that the erosive nature of the ash assists in con-
 trolling scaling and deposition.   Additionally,  the presence of
 ash  in the sludge may enhance the settling characteristics  of the
 combined waste thus requiring equivalent or even less disposal
volume than  the sum of the volumes required for separate sludge
 and  ash disposal.   Ash may also be required for disposal approaches
 incorporating chemical treatment  (fixation).
                              56

-------
          The foregoing is intended only as a brief discussion
of factors attendant to consideration of separate or combined
collection, handling, and/or disposal of fly ash and sludge.
A detailed discussion and analysis of these and other factors
is beyond the scope of this report.

          It appears that many utilities that have designed and
installed lime/limestone scrubbing systems have not analyzed
all the variables involved.  At this point in time, probably due
to lack of data,  the utility companies have not indicated a
consistent approach.

          The following section will quantify projected scrubber
sludge production and compare these quantities and related
environmental considerations to those for wastes associated with
a large utility unit and other industries and activities.   Un-
less otherwise noted, quantities of sludge discussed in this
report will be on a wet (50 percent solids) basis including
coal ash.

1.0       Quantification of the Problem

          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 on-stream hours per year (load factor), the mole
ratio of additive to S02, the S02 removal efficiency of the
scrubbing system, the sulfite/sulfate ratio in the sludge, and
the moisture content of the sludge.  Table 1-7 lists typical
values of these various sludge parameters for a typical Eastern
plant, a typical Western plant, and a hypothetical plant
representing the national average expected between 1974 and 1980.
The values listed as the national average represent a mix of
Western and Eastern plants expected in 1980 based on the trends
                              57

-------
Table 1-7.   TYPICAL SLUDGE PRODUCTION PARAMETERS
Sludge Production Parameter
Coal:
Sulfur Content, 70
Ash Content, %
Plant:
Load Factor, %
Coal Usage, Kg/Kwh
Ul
CO
Scrubbing System:
S02 Removal Efficiency, %
Moisture in Sludge, %
CaO/S02 (inlet), Mole Ratio
CaC03/S02 (inlet), Mole Ratio
Sulfite/Sulfate, Mole Ratio
Large Eastern
Plant

3.5
12

65-80
0.4

80-90
20-60
1.0-1.2
1.2-1.5
9:1
Large Western
Plant

0.5-1.0
10

65-80
0.4

85-90
20-60
1.0-1.2
1.2-1.5
9:1
National
Average

3.0
12

73
0.4

85
50
1.0
1.2
9:1

-------
shown by present flue gas desulfurization system orders.  Table
1-8 shows the effects of variations in the assumed values of
these parameters.

          The sulfur content of coal will vary from plant to
plant.  Comparison of Case 1 and Case 4 in Table 1-8 shows that
a 1000 Mw plant burning 3.5 percent S coal would have to dis-
pose of as much as 908,000 metric tons/year (1,000,000 tons/
year) more wet sludge than the same plant burning 0.7 percent
S coal.  The average coal fired in 1980 by controlled systems
is expected to be about 3 percent.

          The SO2 removal efficiency will vary from one flue
gas desulfurization system to the next as a function of local
requirements.   New Eastern plants will require 75-85 percent
S02 removal to meet the new source performance standard of
2.2 g/103 kcal (1.2 Ib S02/106 Btu).   Existing sources are to
be controlled in accordance with the provisions of the state
implementation plans;  for those Eastern systems requiring
control to meet primary ambient air quality standards, S02
removal efficiencies required generally are in the 60-90 per-
cent range.   New Western plants require 0-50 percent S02 removal
to meet new source standards;  however, several Western states'
implementation plans call for 50-175 ppm maximum effluent S02
concentration.   Compliance with these implementation plans will
require as much as 90  percent removal from Western plants.
Comparison of Case 1 and Case 3 shows that lowering S02  removal
from 90 percent to 80  percent could mean handling as much as
27,000 metric  tons/year (30,000 tons/year) less sludge.

          Since unreacted additive is disposed of with the
sludge,  the stoichiometry of lime or limestone addition (that
is,  the CaO/S02  or CaC03/S02  mole ratio)  greatly influences
                              59

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Table 1-8.   TYPICAL QUANTITIES OF ASH AND SLUDGE PRODUCED BY A  1000 MW COAL-FIRED GENERATING
 STATION CONTROLLED WITH  LIME/LIMESTONE FLUE GAS DESULFURIZATION SYSTEMS,  SHORT TONS PER YEAR a
Case 1 Case 2
Base Case Effect of Stoichiometry
Coal ash, dry
Coal ash, wet (80% solids)
Limestone Sludge, dry
CaS03-l/2H20
CaS04-2H20
CaCOi unreacted
Total
Limestone Sludge, wet 1
(507. solids)
Lime st onp Sludge, wet 1
(with ash. 507. solids)
Lime Sludge , dry
CaS03-l/2H20
CaS04*2H20
CaO unreacted
Total
Lime Sludge, wet
(507. solids)
Lime Sludge, wet 1
(with ash. 507. solids)
a Assumptions:
Coal: I S
% ash
Plant: hr/yr
Ib coal/Kwh
Scrubber: % SO? removal
CaO/S02 mole ratio
CaCOi/SOo mole ratio
1 sulfite oxidation
338,000
423,000
322,000
48,000
185,000
555,000
,110,000
,790,000
322.000
48,000
52,000
az2,uuO
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 ,OdO
924,000
1,600,000
322,000
48.000
17,000
IHT'.dO'O
774,000
1,450,000
3.5
12
6400
0.88
90
1.0
1.2
10
Case 3
Effect of S02
Removal Efficiency
338,000
423,000
286,000
42,000
216,000
544,000
1,090,000
1,760,000
286.000
42,000
69,000
397,000
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
1980
National Average
338,000
423,000
261,000
39.000
92,000
392,000
784,000
1,460,000
261,000
39,000
22,000
322,000
644,000
1,320,000
3.0
12
6400
0.88
85
1.0
1.2
10

-------
the amount of sludge to be handled.  Comparison of Case 1 and
Case 2 shows that lowering the CaO/S02 mole ratio from 1.2 to
1.0 could lower the amount of sludge to be disposed of as much
as 64,000 metric tons/year (70,000 tons/year).  Lowering the
CaC03/S02 mole ratio from 1.5 to 1.2 would result in 173,000
metric tons/year (190,000 tons/year) less sludge.  The CaO/S02
and CaC03/S02 mole ratios vary from system to system at present,
but the general trend is toward lower values as operating
experience is gained.  It is expected that reasonable values for
this ratio in 1980 will be 1.0 and 1.2 for lime and limestone
scrubbing, respectively.

          Other factors influencing the amount of sludge to
be handled are the load factor of the plant, the coal use rate,
and the mole ratio of sulfite to sulfate in the sludge.  The
amount of sludge produced by a plant is directly proportional
to the number of hours per year that the plant operates and the
coal usage of the plant.  The 6400 hr/year and 0.4 Kg/Kwh (0.88 Ib
coal/Kwh) values used for those calculations are typical of
large modern generating stations (Ref. 31, 32).  Obviously if
the plant is on line a larger fraction of the year, the amount
of sludge produced will increase.  The sulfite to sulfate ratio
in the sludge affects the weight of the sludge produced, as
CaS(V2H20 is heavier than CaS03-%H20.  The ratio assumed in this
report (9:1) is taken from the SOCTAP report (Ref. 23).  However,
some system designers are considering trying to completely
oxidize the sludge to improve settling characteristics and de-
crease chemical oxygen demand.  If this were done on a widespread
basis, the weight of dry sludge produced per plant would increase
but improved settling characteristics would tend to lower the
proportion of water in the sludge.
                              61

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          Assuming the forecast demand for FGD control scrubbing
previously discussed is accomplished entirely by lime/limestone
scrubbing* and the national average annual sludge production
rates per 1000 Mw of controlled generating capacity, the amount
of wet ash-containing sludge (50 percent moisture) that will
have to be disposed of annually by 1980 is predicted to be
119,000,000 metric tons of limestone sludge year (131,000,000
tons/year), or 108,000,000 metric tons of lime sludge/year
(110,000,000 tons/year).

2.0       Comparison of Scrubber Sludge with Analogous
          Environmental Problems

          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, including some from the
mining industry, for completeness.

          As shown in Table 1-9, the annual land and solid
waste impact of a 1000 Mw coal-fired electric energy system
equipped with flue gas desulfurization (FGD) for SO  and par-
                                                   3C
ticulate removal is 30,000-35,000 acres,  depending on whether
deep mining or surface mining of coal is used.  The coal mining
operations appear to have the greatest impact in terms of land
«
 It is unlikely that all coal-fired utility FGD installations
will be lime/limestone systems.  However, the majority are ex-
pected to be, and other applications (e.g., oil-fired utility
boilers, coal-fired industrial boilers) could make the projected
sludge production figure quite realistic.
                              62

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                          Table 1-9   COMPARATIVE LAND AND SOLID WASTE IMl'ACT OF 1,000 MW I-LHCTRIC ENERGY SYSTCM  (0.75  LOAD FACTOR)

                    (LOW LEVELS OF ENVIRONMENTAL CONTROLS EXCEPT FOR INSTALLATION OF A LIMESTONE FGD SYSTEM FOR SOy AND PARTICIPATE REMOVAL)


Land Affected,

Annual Solid
Waste Produced,
short tons



Environmental
Impact


Typical Tech-
nique^)
Available to
Minimize
Impact






Mining (C
Deep
9,120

97,141 (wet,
97% solids)
(101,346 with
acid drainage
sludge)


1) Potential
land degra-
dation due
to subsi-
dence ;
2) Acid mine
drainage
water pollu-
tion problems

1) No well
developed
cost-effec-
tive tech-
nology to
sidence;
2) Neutraliz-
ation of mine
drainage with
lime


oal)3
Surface
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
tralization
of mine
drainage with
lime




Processing3
161

454,092 (wet,
997. solids)



1) Culm piles;
2) Water pollu-
tion: a) acid
drainage;
b) siltation;
3) Air pollu-
tion: a) dis-
charges S02, CO
& H2S; b) poten-
tial spontan-
eous combustion

Compacting in
holes, mines,
quarries, etc.






Transport3
2,213


zero



Use of
land for
railroad
beds


N/A






Conversion3
(Plant Site
350


zero



Use of land
for power
plant sice


N/A





Limestone FGD
System,
Untreated b
367
(30 ft. depth)

1,460,000 (wet,
50% solids)



1) Potential
groundwater
pollution
problems;
2) Land poten-
tially made
useless if
sludge not
Created or
permanently
dewatered

1) Although
reclamation is
feasible, no
well developed,
cost-effective

Transmission3
17,188


zero



Use of land
for trans-
mission line
right of way


N/A

Totals
29,399


2.011,233



N/A


N/A
34,289


4.676.092



N/A


N/A
technology has
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 wacer
pollution and land reclamation problems.)
CTl
                  33
             See Table 1-8 (Case 5) for assumptions  (also includes ash)

            GLand affected is expressed as a tine average of the anount of land in
             at its full anount. average variables use  (vraste storage) is 15 tines
use over 30 years.  Fixed land is tal-en
the annual incremental damage.

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use and environmental effects.  Although the right-of-way
required for transmission lines actually consumes far more land
than coal mining, this land is still available for other uses,
public or private, and aside from aesthetics, the environmental
effects are minimal.  As transmission voltages get higher,
however, the economics of larger more numerous conductors,
grounding techniques, and transmission line height versus corona
discharge and potential danger of induced shocks may result
in the purchase and fencing of rights-of-way.  This could take
more land out of production than the right-of-way itself
(Ref.  34).
SO
  x
          A plant equipped with a lime/limestone FGD system for
     and particulate removal and using ponding for disposal will
require just over two times as much total area as a plant site
without SOX or particulate control systems and 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 SOX wastes generated by the FGD system.

          Table 1-9 also shows that large quantities of wastes
are  handled by coal mining and processing operations.   It can be
seen that an FGD system will produce quantities of solids
roughly comparable to the mining operation (about three times
greater than the deep mines,  but about half that for strip
mines).

          Table 1-10 presents a preliminary,  semiquantitative
comparison of most major U.  S.  solid wastes on an as-disposed-
of basis.   In addition to quantities of waste,  typical com-
positions,  disposal methods,  potential environmental problems,
and disposal costs are shown.   Quantities are  not directly
                              64

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                                                Table  I-10.  COMPARISON  OF MAJOR SOLID  WASTE DISPOSAL PROBLEMS
Waste Material
Municipal and
Industrial
Refuse3
Culm PilesC
Mineral Ore
Wastes6
Coal Ash
Limestone
Scrubber
Sludge
(excluding
coal ash)
Quantity Disposed
Annually in Referenced Year,
metric tons, as disposed of
360,000, 000b (1973)
(75% solids)
>91,000,000d (1969)
(dry basis)
1, 300, 000, 000f (1970)
(dry basis)
95, 000. 000 g (1980)
(80% solids)
64, 000, 000 i (1980)
(50% solids)
(119,000,000 including ash)
Composition
40% municipal refuse,
60% industrial refuse
Typical Composition:
paper waste (447.); food
waste 08%) ; glass and
ceramic wastes (9%) ;
garden waste (87.); rocks,
dirt, etc, (4%); plastics,
rubber, leather, textile,
wood wastes (8%).
Waste coal, slate,
carbonaceous &
pyricic shales, clay,
trace metals
Rock waste from mining
operations
Solids Composition (wt 7.1 h
SiO? (30-50), Alo03
(20-30), Fe203 (10-30),
CaO (1.5-4.7), K20 (1-3),
MgO (0.5-1.1), Na20 (0.4-
1.5), TiO, (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-
cures of CaS03-feH20,
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
Considerations
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
with Minimal
Pollution Control
Undefined ground-
water & surface
water pollution;
potential air
pollution
(incinerator
emtnissions, 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 (incinera
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)
CT>

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Table I-10  (Continued)  COMPARISON OF MAJOR SOLID WASTE DISPOSAL PROBLEMS
Waste Material
Municipal
Sewage Sludge
Phosphate .
Rock Slime
Acid Mine
Drainage
Sludge7*1
Gypsum From
Fertilizer k
Manufacture
Quantity Disposed
Annually in Referenced Year,
metric tons, as disposed of
55,000, Q00b(1980)
(0.1-207. solids)
760,000,000* (1970)
(4-6% solids)
8,200,000n(1973)
(1-5% solids)
28,000,000P(1973)
(85-90% solids)
Composition
Composition of Raw.
Primary Sludge, %:J
Volatile matter - 60-80
Ash - 20-40
Insoluble ash - 17-35
Creases & fats - 7-35
Protein - 22-28
N1I4N03 - 1-3.5
P205 - 1-1.5
Cellulose - 10-13
Trace metals
Solids Composition (wt X)1
P2Os (9-17), AlpOi (6-
18), SiO, (31-46), CaO
(14-23), Fe203 (3-7),
MgO (1-2), C02 (0-1),
F (0-1), BPL (19-37),
LOI (9-16), trace
metals
Typical Solids
Composition (wt %)°
CaSOA (40 ;, MgO (1),
MgSO* (5), Fe203 (15),
CaO (3) , Mn203 fr) ,
Si02 (20), &1203 (12),
trace metals
Chiefly CaSOA-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 , S/ton
0.50-10
0.03-0.05
0.04-0.25
"" ™

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                                   Table  I-10  (Continued)  COMPARISON OF MAJOR SOLID WASTE DISPOSAL PROBLEMS
Waste Material
Taconite
Tailings














Quantity Disposed
Annually in Referenced Year,
metric tons, as disposed of
1,100, 000, 000q(1971)
(4-5% solids)














Composition
Typical Solids r
Composition CZ) :
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. S/ton
0.005-0.05
(lake
dumping)













  Exclusive of agricultural  and  mining  wastes.
  Ref.  35.
  Bituminous coal only.
  Ref.  36.
  Mining wastes from metal and non-metallic ores,  exclusive of fossil fuels; no processing wastes included.
  Ref.  37.
^Assumptions:   127. ash,  6400 hr/yr,  248,000 Mw  installed coal-fired generating capacity  (1980), 0.4 kg coal/Kwh
  Ref.  38.
  Assumptions:  37. S, 12%  ash 6400 hr/yr, 90,000 Mw controlled generating capacity, 85% SO, removal, 0.4 kg coal/Kwh.  1.2  CaCO,/SO
  (inlet) mole  ratio,  10% oxidation.                                                      «         to                    32
J Ref.  39.
  80% disposed  of in Florida.
rRef.  40.
  Most  acid  mine  drainage comes  from  abandoned mines and receives no treatment.
"Ref.  41
°Ref.  42.
pRef.  43.
IAS sumptions: >100 million  tons crude  taconite  ore annually, 25% average iron content, 60% beneficiation.
r Ref.  44.

-------
 comparable since they are based on many different sources and
 time periods.

           Considering the quantities of wastes disposed of on
 a wet or as-disposed-of basis,  of those wastes surveyed in
 Table I-10,  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 magnitude greater than the  projected sludge production
 rate,  while phosphate slimes and municipal/industrial  refuse
 also greatly exceed sludge in amounts generated.   Culm pile
 material and projected coal ash from utilities without FGD sys-
 tems are generated  in amounts slightly  greater than projected
 sludge,  while 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 providing varying degrees of sur-
 face and groundwater pollution depending on their chemical
 compositions  and solubilities, and  the location,  design, and
 operation of  the disposal  site.  With proper site selection and
 design (possibly including a permanent impermeable liner) and
 sound operating practices, however, surface water and ground-
water pollution can be avoided.

          For land reclamation, most of the stable wastes will
require only a cover material to support growth of vegetation
                             68

-------
and to prevent eventual erosion 9f wastes by run-off water.
However, some wastes (phosphate rock slime, sewage sludge, un-
treated scrubber sludges) are very resistant to dewatering and
could reslurry in the pond or landfill.  In some cases, these
disposal sites could become only a temporary storage site which
could present a deferred disposal problem as well as a difficult
land reclamation problem.  Fixation technology, now commercially
available and applied at several full-scale installations,
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 dis-
posal by an oxidation process.

          Costs for waste disposal vary greatly depending on the
treatment and transportation of the wastes.  Disposal costs are
minimal for phosphate rock slime and similar wastes which typi-
cally 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 on-site disposal in an unlined pond.
The high end represents steps to solve both the land reclamation
and water pollution problems by chemical treatment and trans-
portation to an off-site landfill.   Discharge of scrubber sludge
to a lined pond solves  the water pollution problem only, and
based on available data, cost would be, as a minimum, $0.50/wet
ton and could be considerably higher.

          In summary, based on preliminary comparisons of avail-
able information on quantities, compositions, and current dis-
posal 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,
                              69

-------
municipal industrial refuse, and coal ash.  Significant quanti-
ties of scrubber sludge are projected for 1980, but waste dis-
posal 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 avail-
able technology has the potential for environmentally acceptable
disposal.   Furthermore, solutions to achieve satisfactory dis-
posal will be influenced by emerging environmental restrictions.
Research efforts to thoroughly evaluate potential hazards and
available technology is continuing through government-funded
contractors, utilities, and fixation technology vendors.

D.        RELATIONSHIP BETWEEN SULFUR OXIDE SCRUBBER SLUDGE.
          STANDARDS/REGULATIONS, AND ENFORCEMENT

          In this section, the relationship between sludge and
current or proposed federal pollution laws and standards and
their implementation and enforcement will be discussed for each
medium--air, water, and solid waste.

1.0       Air

          Pursuant to the Clean Air Act as amended in 1970,  the
Environmental Protection Agency promulgated National Primary
and Secondary Ambient Air Quality Standards (NAAQS) and New
Source Performance Standards (NSPS) in April and December of
1971, respectively.  NAAQS for sulfur dioxide and other pollutants
apply to all areas of the nation.  Resulting state implementation
plans restrict S02 emissions from significant sources.  Since
fossil fuel-fired power plants are large S02 emitters, most
implementation plans limit emissions from these sources to at
least some degree.  NSPS apply to new fossil fuel-fired steam
generators larger than about 25 megawatts capacity.
                              70

-------
          Analysis by EPA's Office of Air and Waste Management
 (OAWM) indicates that the principal areas of the country affected
by SO2 from steam generators lie within EPA Regions III, IV,
and V and Four Corners Air Quality Control Region (AQCR).   Regions
III, IV, and V consumed about 84 percent of the coal used in
1971 and contain the largest number of AQCR's rated Priority I
and IA for S02.  These priorities are indicative of the highest
ambient air concentrations.  It is important to note that about
half of the coal estimated to be used in 1975 will be burned in
these Priority I and IA AQCR's.  Regions III, IV, and V also
include those states that produce most of the high-sulfur coal
in the country.  Most of the states have found or will find it
necessary to issue regulations limiting S02 emissions from steam
generators.  In many cases, flue gas desulfurization (FGD) will
be necessary to achieve emission levels consistent with primary
and secondary ambient air quality standards.  Current schedules
require that activities resulting in FGD system installation be
initiated already or within the next few years.

          Since the subject of FGD systems is vital to the aims
of the Clean Air Act of 1970,  EPA initiated national hearings
which extended from October 18 through November 2, 1973.
Testimony was offered by utilities as well as vendors of FGD
systems and sludge handling processes, fuel suppliers,  state,
local, and federal officials,  and other interested parties.
The hearing panel found that sulfur oxide scrubbing technology
was generally available but that the utility industry considers
the disposal of solid waste (sludge) generated by the throwaway
class of FGD systems to be a major problem.  Two potential
environmental problems associated with uncontrolled sludge dis-
posal were mentioned:   water pollution and land deterioration.
However,  during the course of the hearings, technology was
described which has the potential for minimizing or eliminating
these problems.  This technology includes closed-loop operation,
                              71

-------
 use  of  pond  liners,  and  chemical  treatment  (fixation) enabling
 disposal  of  an  acceptable  landfill material.

          The panel  believes  that a  large number of appropriate
 landfill  sites  are available  for  sludge disposal.  There are
 specific  applications, generally  in  urban areas, where sludge
 disposal  could  be expensive due to lack of readily available
 landfill  sites.  The panel recommends  that regenerable or
 salable product FGD  systems which do not produce throwaway
 sludges or fuel switching be  considered for these applications.

 2.0       Water

          Two areas  of concern have  been addressed in two major
 pieces of legislation dealing with water quality—surface water
 and groundwater.  The Federal Water  Pollution Control Act
 (FWPCA) Amendments of 1972 strongly  address surface waters,
while the Safe  Drinking Water Act of 1974 is directed toward
preservation of groundwater quality.

          The objective of the FWPCA Amendments, enacted
October 1972, is the restoration and maintenance of the
chemical,  physical and biological integrity of the Nation's
waters.   With the national goal that the discharge of pollutants
into navigable waters be eliminated by 1985,  the act requires
the EPA Administrator to:

          1.   Develop and keep updated criteria for
              water quality (including groundwater),
              accurately reflecting the latest knowl-
              edge and information related to effects
              on health and welfare from the presence
              of pollutants,  as well as the factors
              necessary for restoration and maintenance.
                              72

-------
2.  Develop guidelines for effluent
    limitations for point sources,
    other than publicly owned treat-
    ment works, to be met July 1, 1977,
    using best practicable technology
    currently available.

3.  Develop guidelines for effluent
    limitations for point sources,
    other than publicly owned treatment
    works, to be met July 1, 1983, using
    best available technology economically
    achievable.

4.  Develop and keep updated guidelines
    for identifying and evaluating the
    nature and extent of nonpoint sources
    of pollutants and processes,  methods,
    etc. to control pollution.

5.  Develop standards of performance,
    including zero discharge, where
    practicable,  for pollutant effluent
    from new point sources,  other than
    publicly owned treatment works, using
    best available demonstrated control
    technology.

6.  Develop more  stringent limitations, if
    necessary,  to meet water quality
    standards.
                    73

-------
          7.  Develop and keep updated effluent
              standards for toxic pollutants or
              combinations of such pollutants.

          A number of requirements relate to effluents from
point sources.  In the case of a power plant with a lime/limestone
scrubbing flue gas desulfurization system, this would influence
the extent of scrubber liquor bleed.   Completely closed-loop
operation, which is most desirable for FGD system economics
as well as avoiding water pollution problems, would have no
bleed per se.  Liquor would leave the system by only two means--
water evaporative losses in the scrubber and that liquor asso-
ciated with the sludge.  In addition, a number of requirements
relate to water quality (including groundwater) from nonpoint
sources such as ponds and landfills.

          The FWPCA Amendments appear to encompass any pollutant
discharge with the potential for degrading water quality directly
through seepage, discharge, or runoff, or indirectly through
groundwater contamination.

          The Safe Drinking Water Act of 1974 further emphasizes
the need for protection of groundwater supplies.  The Act re-
quires all states to develop effective underground-water pro-
tection programs utilizing money, manpower, and guidance from
the federal government.

          To meet the responsibilities of these pieces of
legislation, additional information characterizing chemical
and physical properties of FGD sludge and associated liquors
is desirable.  Also, treatment techniques and cost effective
and environmentally acceptable disposal require further defini-
tion.  Programs which are planned and underway will provide
this necessary information.
                              74

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3.0       Solid Waste

          There are currently a number of solid waste bills
before Congress that might affect the handling of lime/limestone
scrubber sludge.  When enacted, the provisions would be carried
out by the Office of Solid Waste Management Programs (OSWMP).

          The impact of the enacted Federal Water Pollution
Control Amendments (FWPCA) of 1972 and the proposed solid waste
management acts cannot be fully evaluated at this time.  However,
the implementation of both acts requires EPA to issue guidelines
and limitations regarding water discharge and waste disposal.
These guidelines will be issued and periodically updated on the
basis of best available control technology.  Additional informa-
tion concerning chemical and physical characteristics of the
flue gas desulfurization system liquors and sludge, and of their
potential handling and disposal techniques, will ensure responsible
implementation of this legislation.

E.        NATURE OF THE MATERIAL

          The environmental effects of sludge disposal will be
dictated by the chemical and physical properties of the material;
these properties may vary widely for different operations.
Important variables include the sulfur and ash content of the
coal, the type of scrubber operation (lime or limestone) and
amount of excess material added, the amount of ash in the sludge,
the type of limestone, type of recycle (closed loop, open loop,
or partially closed loop), and the degree of oxidation of the
sulfite.   Several studies are currently underway to quantify
the influence of these variables.   At the present time it is
not possible to give an analysis which truly represents all
systems.   Those data which are available are summarized in the
following discussion.
                               75

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          It should be noted that only recently has a significant
amount of effort been expended in characterizing sludge materials.
The information presented in this section should be considered
preliminary in nature until additional test data are available.

          Chemical characteristics of sludge are related to
potential water pollution problems, while physical characteristics
influence the land use aspects of disposal such as land degrada-
tion and potential reclamation of disposal sites.   Chemical and
physical characteristics of the sludge will be discussed sepa-
rately in this section of the report.

1.0       Chemical Properties of Sludge and Related Materials

          The potential water pollution problems derived from
the chemical properties of the sludge can be broken down into
the following categories:

          1.   Soluble trace metals-

          2.   Chemical oxygen demand.

          3.   Excessive total dissolved solids.

          4.   Excessive levels of other major
              species,  e.g.,  sulfate, chloride,
              calcium,  and magnesium.

          5.   Excessive suspended solids (some
              of which might  dissolve later).

          Some data have already been generated which help to
put these potential problems  in perspective.  The  great majority
of these data have been generated in laboratory studies, pilot
                              76

-------
 plants,  or large  units  which do  not  have  a lengthy record of
 continuous operation.   It  is expected,  therefore,  that  the
 results  strongly  indicate  those  that would be  obtained  by a
 large  system in continuous operation, but may  not  be  exactly
 the same.   In addition,  almost every system is unique in  terms
 of  the coal,  lime or  limestone,  and  scrubber system parameters;
 therefore,  current results should best  be interpreted as  trends.

           Scrubber sludge  solids consist  mainly of calcium
 sulfite  hemihydrate  (CaS03-%H20), calcium sulfate  dihydrate
 (CaSOi, -2H20),  calcium carbonate  (CaC03),  and fly ash.   Table
 1-11 shows  quantities of these major components in several S02
 scrubber sludges  from specific FGD installations,  and also
 points up  the  variability  in composition  of sludges from  dif-
 ferent operations.  Another  source gives  a typical composition
 for sludge  as  shown in  Table 1-12.

          Trace elements occurring in sludge may originate
 either in  the  coal, the  lime or  limestone,  or  the  makeup  water;
 however, coal  is  generally regarded  as  the primary source.
 A particular element may ultimately be  found in the fly ash,
 bottom ash, flue  gas, or in  the plant's discharge.   Because  coal
 ash and  scrubber  sludge represent similar  disposal problems,
 and because they  are often discarded together,   it  is  desirable
 to know  the chemical composition  of each waste stream for
 assessing their water pollution potential.

          Typical ash components are silica, alumina,  and
hematite; also present are various amounts of minor and trace
 elements, some of which are  considered  toxic.  Data in Table
 1-13 illustrate typical compositions of power plant coal ashes.
The uranium and thorium values represent Eastern coals only;
                              77

-------
                              Table I-11.  CHARACTERISTICS OF SLUDGE FROM OPERATING S02 SCRUBBERS2
CO
Facility
Lawrence 4
Lawrence 5
Hawthorn 3
Hawthorn 4
Will County 1
Stock Island
La Cygne
Cholla
Paddy's Run 6
Mohave 2
Rate (dry basis) ,
metric tons/hr
10.7
34.4
12.4
15.4
17. 5b
2.4
12.5
3.1
5.3
1.5b
Sludge Composition fdrv basis), wt percent
CaS03-l/2H20 C
10
10
20
17
50
20
40
15
94
2
aSO^ • 2H20
40
40
25
23
15
5
15
20
2
95
CaC03
5
5
5
15
20
74
30
0
0
0
Fly Ash
45
45
50
45
51
lc
15
65
4
3
Estimated
Solids Content
of Dewatered Sludge,
wt percent
50
50
40
40
35
50
35
50
40
65
          aRef.  45
          bPrior to stabilization
          cMainly unburned  carbon

-------
      Table 1-12.  CHEMICAL COMPOSITION OF TYPICAL
             DESULFURIZATION SYSTEM SLUDGE3
Fly Ash
CaS03-l/2H20
CaS04-2H20
CaC03
Others
17-2070
6570
5-77,
3%
3-570
aRef. 46
                           79

-------
       Table 1-13.  POWER PLANT COAL ASH COMPOSITIONS3







        Constituent                               -/0 Bv Weight




 Silica (Si08)                                        30-so





 Alumina (A1303)                                      20-30





 Ferric Oxide  (Fe803)                                 10-30





 Lime  (CaO)                                          1.5-4.7





 Potassium Oxide  (K.,0)                               1.0-3.0





 Magnesia (MgO)                                      0.5-1.1





 Sodium Oxide  (NaaO)                                 0.4-1.5





 Titanium Dioxide  (Ti03)                             0.4-1.3





 Sulfur Trioxide (S0a)                               0.2-3.2





 Carbon (C) and volatiles                            0.1-4.0





 Boron  (B)                                           0.1-0.6





 Phosphorus (P)                                     0.01-0.3





Uranium (U) and Thorium (Th)                        0.0-0.1





aRef.  38
                              80

-------
none were  readily available for Western coals.  Table 1-14 shows
the results of analyses of trace elements in  two coal samples, a
fly ash  sample, and a bottom ash sample.  The ash samples are
from a Western coal containing 10 percent ash.  The differences
between  the Eastern coal and the Western coal are notable.
Relative to the Western coal, the Eastern coal is very high in
zinc, manganese, barium, chromium, and vanadium.  The Western
coal is  higher in arsenic, antimony, selenium, and nickel.  It
is also  important to note that the fly ash from both coals is
generally  higher in trace element content than the bottom ash.

           The ultimate fate of a given species in the solid
waste (ash and/or sludge) will be determined  largely by its
solubility.  The major components of sludge have limited solu-
bilities,  while fly ash is even less soluble.  Generally, 2-5
percent  of fly ash is water-soluble.  The resulting solution is
usually  alkaline due to the effect of free lime (CaO) although
some ashes, especially from Eastern coals, produce acidic sluice
waters.   The principal soluble species are calcium and sulfate
ions, with limited amounts of sodium, magnesium, potassium,
and silicate also present.   Table 1-15 contains analyses of ash
leachate from a plant burning acidic coal and sparse information
on ash leachate from a plant fired with alkaline coal.

           Other types of data for predicting potential impact
on water quality due to simultaneous ash/sludge disposal are
analyses of ash ponds.   Ponded fly ash solids from progressive
sampling points through the ash disposal system at the Oak Ridge
Y-12 steam plant were collected.   The analyses are presented in
Table 1-16.  These results may be used to examine the dissolution/
precipitation of a given species with time.   It appears that the
concentration of most of the elements in the solids remains
relatively stable.
                                81

-------
                         Table 1-14.   SELECTED TRACE ELEMENTS IN COALS  AND ASH3
C3
to
Element
Arsenic
Mercury
Antimony
Selenium
Cadmium
Zinc
Manganese
Boron
Barium
Beryllium
Nickel
Chromium
Lead
Vanadium

Eastern Coal
N.D.b
<0.01
<0.05
N.D.
N.D.
180
350
46
1800
<0.01
N.D.
310
30
180

Western Coal
Composite
Sample
3
0.05
0.17
1.6
<0.5
0.56
15
15
400
N.D.
25
5
4
9
Composition, PPM

Samples from Western Coal-Fired Plant
Fly Ash
15
0.03
2.1
18
<0.5
70
150
300
5000
3
70
150
30
150
Bottom Ash
3
<0.01
0.26
1
<0.5
25
150
70
1500
<2
15
70
20
70
    'Ref.  47

    'N.D.  - Not detected.

-------
                               Table 1-15.   ASH  LEACHATE COMPOSITIONS FROM POWER  PLANTS BURNING ACIDIC AND ALKALINE COAL3'b





Parameter
PH
TDS
Alkalinity
Sulfate (SO,,)
Total Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Lead (Pb)
Cadmium (Cd)
Mercury (Hg)
Manganese (Mn)
Arsenic (As)
Power Plane Using Acidic Coal
Actual Discharges
From the Fly Ash
Disposal Site

L-26
2.7b

3460
5167b
815 b
0.05
4.25b

0.30b
0.03b

152.5

L-27
2.75b

2440
39J5b
352. 5b
0.07
3.63b

0.30b
0.03b

142. 5b

L-28
2.5b

4240
4982 b
697. £
0.19
5.13b

<0.10
0.04 b

85b

Hot torn
Ash
T r»
l n
Pond
L-29
5.35


80.75
0.08
<0.01
2.0b

<0.10
0.09b

0.33

Fly Ash From Three
Different Silos


L-30
4.35


777b
0.30
1.37 b
18 . 25b

<0.10
0.09 b

1.09b

L-31
4.0

880
2006b
2.90b
6.75b
22.75b

0.3b
0.15b

2.15b

L-32
4.4

82
464 b
0.10
1.04 b
16.75b

<0.10
0.03b

0.64 b

Power Plants Usine Alkali

Plant 01

Flv Ash
L-33



1620b
<0.05







<0.01
Bottom
Ash
L-34



18
0.15







<0.01

Plant 112

Fly Ash
L-35



1260b
<0.05







<0.01
Bottom
Ash
L-36



150
<0.05







<0.01
pe COA 1

Plant //3
Bottom
Ash
L-37



42
<0.05







<0.01

Fly ^ch
L-3G



1500 b
< 0.05







<0.01
CO
                  aRef. 48
                   Exceeds  stream  criteria

-------
         Table  1-16.   ANALYSES  OF DRY FLY ASH SOLIDS

                 FROM THE Y-12  STEAM PLANT3'b
Element
Aluminum
Barium
Boron
Calcium
Chromium
Copper
Iron
Lead
Lithium
Magnesium
Manganese
Nickel
Potassium
Silicon
Sodium
Titanium
Vanadium
Composition, Wt Percent0
Sample A
>20
0.12
0.03
0.6
0.03
0.02
10
0.01
0.04
0.6
0.04
0.02
-
20
0.6
0.3
0.03
Sample B
20
0.12
0.05
0.6
0.03
0.03
10
<0.01
0.08
1.0
0.04
0.03
3
35
0.7
1.0
0.04
Sample C
18
0.10
0.05
0.6
0.03
0.03
7
<0.01
0.08
0.9
0.08
0.03
2.5
30
0.6
0.8
0.08
 Ref.  49

 These samples  are  from the  Oak  Ridge  Y-12  steam plant.
 Sample A was collected at the overflow  from  the primary
 retention basin  to  a water  filled  quarry which acts as a
 settling pond.   Sample B was collected  at  the outfall of
 the quarry, and  Sample C was collected  where the overflow
 enters a lagoon  of  a lake.
*
 Compositions determined by  spectrographic  methods.  All
 other elements present in quantities  less  than their
 detectable limits.
                           84

-------
          Table 1-17 characterizes the ash pond discharge from
TVA's Widows Creek Station over a period of 1 year.  Trace
element composition of an unidentified ash pond is compared to
Public Health Service (PHS) Drinking Water Standards in Table
1-18.  Manganese and selenium exceeded the limits for this
particular sample.

          A minor portion of trace elements may also be intro-
duced into the sludge with the lime or limestone and makeup
water.  Several analyses of different limestone additives are
given in Tables 1-19 through 1-22.

          The final distribution of the trace elements in the
solid and liquid phases can be useful in predicting whether a
water pollution problem exists,  either from the pond effluent
or from landfill leachate.  Table 1-19 presents analyses of
metals and other trace species for the solids collected at
various points in TVA's limestone scrubbing system at Shawnee.
Concentrations of these species  in samples of coal and limestone
used in the system are also shown.  In Table 1-20 the relative
amounts of metals in the clarifier solids are compared with those
in the liquid associated with the solids from the same scrubber
operating in partially closed loop.  As might be expected,
sodium, potassium, magnesium, and calcium are soluble.  In ad-
dition, such species as boron, molybdenum, manganese, silicon,
and copper also occur at significantly higher levels in the
liquid.  Other trace metal species are concentrated in the
solids.  It should be noted that equilibrium may or may not have
been reached;  i.e., given time,  additional solids might dissolve.

          The concentrations of  various species in the solids
and liquid effluents from a centrifuge can be compared in
                              85

-------
                          Table  1-17.   CHEMICAL  ANALYSES  OF ASH POND DISCHARGE FROM TVA'S WIDOWS CREEK3
CO
Concentration, ppm
Sample
Identity
1971 Quarterly
Samples, TVA's
Widows Creek

PH
7.3
9.0
9.8
9.1
Total
Solids
250
190
210
210
Total
Dissolved
Solids
240
190
210
210
Alkalinity,
Total
CaCO-
34
45
61
75
Total
Hardness.
CaC03
69
99
130
130
Ca^
20
34
47
45
Mg
4.6
3.4
3.7
4.3
so4
100
95
70
60
Cl
21
11
19
17
Si02
5.4
4.4
6.1
5.6
Fe
0.29
0.42
0.27
0.69-
Mn
0.44
0.02
<0.01
0.02
       a
        Ref. 50

-------
          Table 1-18.   SELECTED ELEMENTS IN SOLUTION
a,b
Element
Lead
Antimony
Barium
Manganese
Mercury
Beryllium
Boron
Nickel
Cadmium
Selenium
Zinc
Arsenic

Ash Pond
Liquor
0.01
0.015
0.07
0.075
<0.001
0.002
0.5
0.015
0.01
0.035
0.03
0.01
Concentration, ppm
Scrubber Liquor
(Aerospace Data)
<0.01
N.D.C
<0.05
1.6
N.D.
N.D.
11
0.05
CT.D.
N.D.
N.D.
N.D.

PHS Drinking
Water Standard
0.05

1
0.05




0.01
0.01
5
0.05
 Ref.  47


3The ash  pond data  represent  approximate  levels which

 might normally occur.   The scrubber  liquor  is analysis

 of an unspecified  sludge  liquor.
•^

 N.D.  - Not  detected.
                            87

-------
                                      Table 1-19.  SPARK SOURCE MASS SPECTROGRAPHIC ANALYSIS  OF SCRUBBER SOLIDS3
00
00
Concentration, ppra

Element
LI
B
C
N
F
Na
'Mg
Al
P
S
Cl
K
Tl
V
Cr
Mn
Fe
Cu
Zn
As
Rb
Sr
V
Cs
Ba
Pb
BT

Coal
3.3
46
<»!*>
30
7.9
1.700
1.700
7,500
40
C>1*>
280
3.000
5.900
180
310
350
4,500
N.D.e
180
N.D.
24
1.100
93
N.D.
1,800
30
N.D.

Limestone
1.8
1.5
4,900
4.5
12
360
<>1X)
4,200
85
220
38
580
440
15
76
140
2,500
N.D.
59
N.D.
1.7
1.500
N.D.
N.D.
10
N.D.
N.D.
TCA Effluent
Separated
Solids b.c.d
5.1
28
1.700
1
30
2,800
<>!*>
(•>!%)
170
(>ll)
47
3,700
4,500
94
240
180
(>1Z)
33
330
24
13
750
63
1
1,600
20
N.D.

TCA Effluent h -
Slurry Solids '
7.9
42
170
3
16
290
(>1%)
(>ll)
150
2.100
79
760
5,300
150
250
230
(>IX)
49
450
33
30
1.500
45
1.2
870
64
N.D.

Clarifler
Solids *>
1.2
7.6
140
3
5.9
270
(•»17.)
(»!*)
110
330
42
860
4,200
ISO
66
190
(>1Z)
N.D.
90
16
9.0
1,100
27
N.D.
520
N.D.
N.D.

Bottom
42
220
2,500
3
4.1
350
9.700
(•>1X)
680
200
17
1.300
(>1Z)
290
700
530
(>1Z)
220
640
3
63
170
340
6.0
<»«)
R.D.
R.D.
Fly

TCA
Inlet
6.5
38
2,000
5.1
4.2
870
4,400
• „
140
440
25
960
6.000
65
440
180
mm
25
290
22
11
400
73
1.3
1.000
27
6.5
Ash

TCA
Outlet
13
220
7,000
230
30
2,800
5.700
— —
1.800
1,200
58
2.500
(>ll)
820
230
290
mm
140
1,600
450
40
1,300
47
1.4
6,400
64
N.D.
              *Hef.' 51
              bSanple for Columns 4. 5.  and  6 were centrifuged and dried at Aerospace.
              'Samples for Columns 4 and 5 were obtained upstream of the clarlfier.
              ^Column 4 sample was filtered  at the scrubber site.
              *H.D. - Hot detected.

-------
       Table 1-20.  EMISSION SPECTROGRAPHIC ANALYSES OF
           LIMESTONE AND CLARIFIER LIQUOR AND SOLIDS
                                                    a
Speciesb
Ca
ME
Si
B
Hn
Fe
Al
Mo
Cu
Na
Ni
Sr
K
Co
Cr
Ti
Pb
Ca
Other
Cations
Distilled
Water ,
ppm
Q
TR < 0.004
0.0040
0.085
d 0.018
N.D. < 0.01
0.055
< 0.04
< 0.02
0.0064
N.D. < 1.0
0.058
N.D. < 0.01
N.D. < 2.0
Nil
Nil
Nil
Nil
Nil
Nil
Clarifier
Liquor,
ppm
1100.
67.
14.
11.
1.6
0.17
0.34
0.56
0.0017
TR < 7.5
0.05
2.1
19.
Nil
Nil
Nil
Nil
Nil
Nil
Clarifier
Solids,
Wt 7«
27.
1.4
8.9
6.0092
0.013
0.25
2.6
Nil
0.00053
0.23
0.0017
0.099
0.88
TR < 0.001
0.0025
0.53
0.015
0.0027
Nil
Limestone,
Wt %
35.
2.9
0.65
N.D.< 0.005
0.011
0.10
0.012
Nil
0.00011
0.036
N.D.< 0.001
0.078
N.D.< 0.20
N.D.< 0.001
0.00084
N.D..< 0.003
N.D.< 0.01
N-D-< 0.002
Nil
aRef.  51.
 Balance is sulfate,  sulfite,  oxides,  and  carbonates.
:TR -  Trace
 N.D.  -  Not detected
                              89

-------
Table 1-21.  These data are from a limestone turbulent contact
absorber (TCA) scrubber pilot plant;  the fuel was a Western coal.
It can be seen that many metals are concentrated in the liquid
phase, including iron, aluminum, magnesium, sodium, boron,
titanium, manganese, chromium, copper, and nickel.   The pH of
this liquid is not known, but a low pH might account for the
high metal solubility.  In Table 1-22 the relative content of
metals in the limestone versus the centrifuged solids can be
compared for this same pilot plant.  These data were obtained
employing a different analytical technique.  Table 1-23 shows
some typical sludge liquor compositions and compares them to
EPA proposed water quality criteria.   The concentrations of
arsenic, cadmium, chromium, mercury,  boron, chloride, and sul-
fate exceed the limits in at least one case.  Other sources
have reported other elements such as  cadmium, selenium, nickel,
and magnesium to be in excess of various water standards.   Sul-
fate, chloride, and total dissolved solids are often in excess
of the limits.

          Chlorides and trace metals  which are volatilized and/
or form ultrafine particulates during coal combustion are
collected in the scrubber.  This indicates the multipollutant
control potential of FGD systems.   Approximately 95 percent of
the chloride in the coal has been found to be evolved as HC1 in
the combustion gases (Ref. 53),  Oak  Ridge National Laboratory
found that electrostatic precipitators were efficient for most
elements contained in the fly ash.  However, mercury, selenium,
and possibly arsenic, were noted as exceptions.   Approximately
90 percent of the mercury in the coal was estimated to be
unaffected by the precipitator (Ref.  54).

          The effect of pH on trace metal solubility is cur-
rently under investigation.  Preliminary results from an Aerospace
                              90

-------
   Table  1-21.   EMISSION SPECTROGRAFHIC ANALYSIS OF SOLIDS FROM A WESTER!; STATION3
Composition, wt %
Element
Si
Ca
Fe
Al
Mg
Na
Ba
B
P
Ti.
Mn
> K
Pb
Ga
Cr
Mo
Sn
V
Cu
Zn
Ni
Co
Sr
Other
Scrubber Input
From Holding Tank



N.D.C<
TR <
N.D. <


TR <
TR <
N.D. <

N.D. <
N.D. <
N.D. <

N.D. <

N.D. <


10.
25.
1.2
3.4
0.53
2.4
0.20
0.005
0.50
0.10
0.017
0.40
0.02
0.006
0.0071
0.004
0.008
0.008
0.0041
0.06
0.0024
0.002
0.030
Nil
Scrubber Output
To Holding Tank
1.
35.
0.
0.
0.
1.
—
0.
—
0.
0.
TR < 0.
0.
--
0.
--
—
--
0.
—
0.
—
0.
-—
6
29
90
18
6
-
0063
-
056
0076
40
016
-
0070
-
-
-
0025
-
0041
-
11
-
Centrifuged
Solids
1
37
0
0
0
0
-
TR < 0
-
0
0
-
TR < 0
-
0
-
-
-
0
-
0
-
0
-
.4
.18
.79
.20
.69
—
.005
--
.044
.0055
--
.01
--
.0042
--
--
--
.00089
--
.0029
--
.14
-—
Make-Up
Centrate Water
18
4
3
15
1
5
0
0
TR < 0
0
0
0
0
0
0
0
-
0
0
-
0
0
0
-
.2
.6
.3
.2 TR <
.19 TR <
.016
.50
.94
.046
.94 N.D. <
.064
.024 TR *
.072
.0088 N.D. *
TR •>
.030 N.D. >
.036
--
.014
.0043 TR <
.095
--
22.
9.6
4.2
6.2
1.4
0.20
0.20
0.017
2.6
0.12
0.13
0.40
0.034
0.006
0.038
0.004
0.008
0.008
0.38
0.86
0.0028
0.002
0.16
---
Limestone


TR <
N.D. <
N.D. <
N.D. <
N.D. <


N.D. <
N.D. <


N.D. <


N.D. <
N.D. <
N.D. <


0.24
39.
0.070
0.0099
0.30
0.06
0.20
0.005
0.50
0.004
0.025
	
0.01
0.006
0.0014
	
0.008
	
0.00022
0.06
0.002
0.002
0.039
---
jjRef.  51.
 N.D. - None detected.
CTR - Trace

-------
Table 1-22.  SPARK SOURCE MASS SPECTROMETRY ANALYSIS
        OF SOLIDS FROM A WESTERN STATION
,a


Element
Li
B
C
N
P
Na
Mg
Al

P
S

Cl
K
Ti
V
Cr
Mn
Fe

Cu
Zn
As
Rb
Sr
Cs
Ba
aRef. 51
DM r» M—J-


Detection
Limit
0.07
0.1
0.1
1
0.1
0.07
0.7
0 5
»•» • — '
0.2
2
fm
0.5
0.1
1
0.5
0.7
0.5
1
Am
1
1
1
0.7
3
3
5



scrubber
Output to
Holding
Tank
7.9
28
920
72
190

7,400


1,100


1,600
1,100
1,100
42
250
90


1
71
58
22
1,700
53
1,400


Composition,

Centrifuged
Solids
5.5
35
5,500
41
3,500

5,600


390


1,400
2,100
3,700
59
290
180


1
210
46
7.3
1,600
N.D.b
2,000


ppm

Limestone
0.31
0.80

2.2
4.3
1,700
4,000

3,300
9
50

30
4.3
330
160
5.3
19
150

900
N.D.b
6 0
V • V
11
0.7
220
N.D.b
N.D.b


                     92

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                                           Table  1-23.   CHEMICAL ANALYSIS OF SLUDGE  LIOUORSa>b


Element
Calcium

Scrubber.
'Size, Mw
'Percent Solids
in Discharge

Magnesium
Boron

Chloride
Fluoride
Sulfate
Sulfite
TDSe
Arsenic




Beryllium
Cadmium

Chromium (total)
Copper
Lead
Mercury



Selenium
Zinc
PH


	 • — • 	 /**,^ „„„«._.. I..- __ — 	 	 . 	 __
TVA Shawnee
Lime
10
50-55
2520
25
40.8
5000
3.3
800
0.9
9000
0 02
0.002
0.10
0.03
0.002
0.5
0.001
0.02
0.08
9
TVA Shawnee
Limestone
10
35-40
1600
600
_d
2500
3.4
2000
110
7000
0.02
0.01
0.005
0.15
0 02
0.1
0.06
0.30
0.30
a
SCE Mohave
Limestone
1
75-30
1400
_d
_d
30,000
3.1
2500
0.1
70,000
0.03
0.001
0.05
0 005
0.03
0.01
0.0012
0.12
0.12
7
ft"" 	
Plant B
Lime
(Eastern coal)
100
35-40c
1400
410
_d
2700
2.6
2250
20
7000
0.085
0.012
0.023
0.040
0 048
0.18
0.045
0.80
0.09
9
Water Quality
Criteria
EPA Proposed
Public Water
Supply Intake

__
1.0
250
— „ _
250
__
110 LIMIT f
0.1
	
0.01
0.05
1 0
0 05
0.002
0.01
5.0
5 to 9
j^Ref. 52.
VO
            Q        fc*  	;	f,	— — »  —--•—• | ~ »•»••*»«»- ^» v»» wu i aviica * ^ I  *"Wt»fc"Ciiii O 4.13114. Ai ^WCIIIU CUiUVUll L.D W J. 
-------
Corporation study indicate that the least environmental hazard
exists at an alkaline pH under reducing conditions.  The
further suggest that there is no set of chemical conditions for
untreated sludge which will eliminate all of the hazards due to
trace metal solubility (Ref. 51).  Soil attenuation mechanisms
will likely reduce the potential hazards and are currently under
study.

          Total dissolved solids (TDS) in scrubber liquors and
from ash liquors vary widely.  Data for TDS are given in Tables
1-17 and 1-23.   The sludge liquor from TVA's Shawnee lime scrub-
bing system was reported to have 7000 ppm TDS in the sludge liquor
The limestone system at SCE's Mohave Station which operates in
a very tight closed loop system reported 70,000 ppm TDS.   Ash
liquor data from Ohio Valley power plants indicate an average
TDS value of 750 ppm (Ref.  38).   Widows Creek ash liquor data
indicate an average of about 230 ppm.   The higher TDS values of
sludge liquors  include calcium and magnesium compounds,  chlorides,
and some trace  elements.   The fact that sludge does contain
significant quantities of soluble material necessitates  careful
disposal of untreated material to avoid environmental problems
in terms of surface or groundwater contamination.

          In summary the  data indicate:

          1.  The solid phase of scrubber sludge
             will consist  essentially of the
             calcium compounds  noted above (See Page 77) .
             These calcium compounts  have a limited solu-
             bility in sludge liquors.   The major components
             of fly ash  are even less soluble.
                              94

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2.  Scrubber sludge and ash solids will
    contain 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 ele-
    ment content of the sludge is minor.

3.  Sludge and ash liquors will contain
    dissolved species from the solid con-
    stituents in accordance with solu-
    bilities which are generally an inverse
    function of pH.   The chemistry of the
    coal, particularly chlorine and sulfur
    content, and the type of scrubber sys-
    tem 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
    multipollutant control potential of
    FGD systems.
                    95

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           5.  Limited  data  indicate total dis-
              solved 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, magnesium
              compounds, trace elements, and
              chlorides.

2.0       Physical Properties and Settling Characteristics
          of Scrubber  Sludges

          As for the chemical properties,  physical properties
of sludge may vary widely,  and may be influenced by many factors
in a manner that is not yet well understood.  It should be noted
that these results are preliminary and may or may not be typical
of large-scale continuous operations.

          The physical properties are important in terms of
sludge disposal since they have an influence on the difficulty
of handling, transporting,  treating,  and ultimately disposing
of the material.   Physical properties also are important in
regard to land reclamation of abandoned disposal sites.

          The areas of potential concern here are:

          1.  Rewatering of the dried,  aged material.

          2.  Strength, i.e.,  load bearing capacity.

          3.  Ability to support vegetation growth
              (chemical properties are  also important
              here) .
                              96

-------
          Particle size measurements have been reported for a
number of sludge compositions (Ref. 55, 56).  Both wet screen
and subsieve analytical techniques were utilized.  The results
are presented in Tables 1-24, 1-25, and 1-26.  Identification
of most of the samples analyzed is included in Table 1-24.  The
results indicate that the particle sizes fall in the range of
silt with minor percentages in the fine sand and clay size
proportions.

          A related parameter, the Elaine index, is a measure
of the total surface area of dry solids.  The Elaine index for
a packed bed of material was determined by measuring the per-
meability by ASTM method C204-55.  The Elaine index was then
determined by its inverse relationship to the permeability.
These results are presented in Table 1-27.

          Permeabilities of settled and freely drained sludge
were reported by Aerospace to be 2.2 - 2.3 x 10~" cm/sec
(depending on column heights).  These values are roughly equiv-
alent to those of fly ash (Ref.  52).  Sulfate sludges have
higher permeabilities than sulfite sludges when both are in
settled states.   Drainability (a property which is directly
related to permeability) of both types of sludges, especially
sulfate sludges, is reduced by up to two orders of magnitude
by compaction and addition of fly ash.

          The bulk density of various scrubber sludges varies
as a function of water content.   As the percent of water
increases from zero, the bulk density increases as the pore
volume becomes filled.  When completely filled, a maximum bulk
density is reached.  With greater percentages of water, a
dilution effect is observed as the bulk density decreases.  For
Shawnee (limestone sludge with fly ash) clarifier underflow
                              97

-------
         Table  1-24.   WET  SIEVE ANALYSIS OF SCRUBBER SLUDGES
                                                            a

Meah +40
Fly Ash 0.2
Eastern Coal Lime Sludgeb
Western Coal Lime Sludgec
Dry Injected /with Wet
Scrubber Sludged
Limestone Scrubber
Sludge6
Smelter Gas Sludgef
Unidentified FGD Sludge
Cumulative
+100
1.7
--
--

--

--
--
1.1
Wt %
+200
7.1
--
—

--

—
--
4.9
Retained
+325
15.1
7.5
--

--

__
--
9.3

+400

13.5
1.0

29.2

18.4
2.4
14.3
aRef.  55, 56.

 Lime scrubbing sludge from a power plant burning Eastern Coal; ash
 present.
p
 Lime scrubbing sludge from a power plant burning Western Coal; no
 ash present.

 Sludge produced by limestone injected into the boiler followed by
 wet scrubbing; ash present.

 Limestone scrubbing sludge from a pilot plant burning oil; no
 ash.

 Lime scrubbing sludge from molybdenum sulfide smelter; no ash
 present.
                                98

-------
     Table 1-25.   SUBSIEVE ANALYSIS OF FLY ASH AND AN
            EASTERN COAL LIME SCRUBBER SLUDGE3
Micron
+50
+40
+30
+20
+17
+15
+10
+ 7
+ 5
+ 2
+ 1
Cumulative
Fly Ash
15
--
--
27
32
--
47
62
--
92
97
Wt % Retained
Eastern Coal Sludge
1
2
5
12
--
21
39
51
68
88
- -
   aRef. 26
             Table 1-26.   SUBSIEVE  ANALYSIS3"

Equivalent Spherical Diameter, microns    Cumulative Wt "%
             +18                                10
             -18                                90
             -12                                80
             -  9                                70
             -  8                                60
             -6.4                               50
             -  5                                40
             -  4                                30
             -  3                                20
             -1-5                               10
                 Blaine  Fineness  Number 7600
  a
    Source:  Micromerities Instrument Corp. as cited in Ref. 56
                              99

-------
       Table 1-27.  ELAINE INDICES FOR SCRUBBER SLUDGESa
     Sample  (refer to Table 1-24)     Elaine Index (cm2/g)

     Fly Ash                                  2,640
     Eastern Coal Sludge                     12,500
     Western Coal Sludge                     27,500
     Dry Injected/Wet Scrubber
       Sludge                                14,100
     Limestone Scrubbing Sludge              11,100
     Smelter Gas Sludge                       3,670
aRef. 55
                             100

-------
samples, the peak bulk density was reported to be 1.7 g/cm3
(106 lb/ft3) at 70 percent solids content.  The bulk density of
a packed and dried Shawnee sample was 1.2 g/cm3 (75 lb/ft3).
These data are compared to the true density of Shawnee solids
equal to 2.5 g/cm3 (155 lb/ft3) (Ref. 51).  Practical dewatering
methods do not remove sufficient water to obtain maximum bulk
densities in the Shawnee sludge.  In comparison, the sludge
from the Mohave power plant also employing a limestone system
was shown to have a maximum bulk density of 1.87 g/cm3 (117
lb/ft3) at 78 percent solids content.  The Mohave scrubber
sludge has a true density of 2.53 g/cm3 and a bulk density of
1.46 g/cm3.  For this sludge, maximum bulk densities can be
achieved by dewatering (Ref. 51).  Based on measurements for
several sludges, Lord reported that typical values for bulk
density of settled sludge range from 1.4 - 1.5 g/cm3 (85 - 95
lb/ft3) (Ref. 56).  Specific gravities of the dry sludge solids
ranged from 2.48 to 2.55.

          Typical packing volumes for settled fly ash, sulfate-
based sludge, and sulfite-type sludge were reported to be 0.6,
1.4 and 2.3 m3 per metric ton (20, 45 and 75 ft3 per ton)
(Ref.  45).   Sulfite sludges will require greater storage volumes
because sulfites tend to crystallize in small, thin platelets
that settle to a loose bulky structure,  occluding a relatively
large amount of water.

          Viscosity measurements for Shawnee limestone scrubber
sludges and limestone scrubber sludges from Mohave have also
been reported (Ref.  51).  The Shawnee samples,  50 - 60 percent
solids, exhibited a viscosity which decreased with stirring
time.   This was due to the thixotropic nature of the sulfite-
laden material.   If the stirrer was shut off for 1 minute,
however, the viscosity returned to a higher value, which then
                             101

-------
decreased with time.  The viscosity measurements ranged from
120 to 20 poise (cf. water, 0.01 poise).  The shear rate was
reported to be 7.9 cm/sec (15.6 ft/min) at 64 rpm.

          The limestone scrubber sludge from the Mohave power
plant displayed markedly different properties due to its high
clay content.  In fact, the sludge settled so rapidly and was
so viscous that measurements were limited to those less than
50 poise.  Some of the especially stiff mixtures  (>65 percent
solids) displayed sporadic rheopectic behavior; i.e., increase
of viscosity with stirring time (Ref.  51).

          TVA has determined the gel strength of a 16 percent
solids sludge from a limestone system employing a torsion wire
gelometer (Ref. 57).  This parameter was found to be a strong
function of time as indicated by the data in Table 1-28.

    Table 1-28.  GEL STRENGTHS OF A LIMESTONE SYSTEM SLUDGE
         Time After Stirring         Strength (g x cm)

                0                             0
               30 min.                        6
               18 hr.                       >25
          Shrinkage of untreated, dried Shawnee sludge was
reported to be a function of water content.  The degree of linear
shrinkage for a molded, air-dried sample was reported to be 3.7
percent (Ref. 51).
                             102

-------
           Compaction  strength  is measured by the resistance of
 wet  sludge to  penetration of a flat bottom ram, 1.0 cm diameter,
 pushed  in  at the  rate of 1.27  cm/min.  This parameter is used
 to evaluate the mechanical  stability and load-bearing capacity
 of ponded  sludge.  This property is a strong function of water
 content.   Results  for Shawnee  and Mohave sludges are presented
 in Figure  1-5.  Shawnee sludge at 45 percent moisture was
 judged  to  lack any appreciable degree of compaction strength;
 however, if dried  to  30 percent water content, it showed a
 substantial increase  in strength to 21,000 - 25,000 kg/m2 (30 -
 35 psi)  (Ref.  51).  The stress  required to support a person is
 "2000 kg/m (3 psi),  which  is  achieved by Shawnee sludge at
 approximately  61 percent solids.  Safe access for personnel can
 probably be granted if the  solids content is greater than 65
 percent, at which  point the load-bearing strength is expected to
 be 5600 kg/m2  (8 psi).  Vacuum filtration can dewater Shawnee
 sludge  to  this extent.  Reduction of moisture content to 30
 percent or  less will  probably be necessary before the sludge
 can   support  the weight of vehicles.

           Bearing  strength for Mohave sludge does not vary
 smoothly as a function of water content.   At 65 percent solids
 a sharp increase in compaction strength occurs, ranging from
 2100 to 21,000 kg/m2  (3 to 30 psi).   Mohave sludge can be de-
watered to  this point by any of the dewatering processes, in-
 cluding settling.   At 65 percent solids,  ponded Mohave sludge
 is probably safe for  equipment and personnel.

          Pozzolanic  strength determinations were made by
applying compression  strength at a constant strain rate to ash-
containing  samples which had been cast in cylindrical molds
and cured for a given time in a humid environment.   Initial
uncured strength was  determined on samples  unmolded after 5 days.
                              103

-------
                        MOHAVE
 30               35               40
       Water Content, Weight Percent
                                  45
Figure 1-5.
Sludge Compaction Strength
 (Ref,- 51).
                  104

-------
Additional  testing was done at 1-month intervals.  This property
reportedly  varied as a function of water content.  Testing was
carried out with an Instron test machine using a cross-head
speed of 0.05 cm/min.  Shawnee sludge samples showed negligible
compressive strength.  Loads of less than 2.3 kg (5 pounds),
equivalent  to strengths of 18,000 kg/m2 (26 psi), were the limits
even after  4 months of curing.  Mohave sludge samples withstood
greater loads when damp (freshly demolded) than when cured for
longer periods.  Uncured samples had strengths of 1.2 x 10s kg/m2
(170 psi) and cured, dried samples measured 7.0 x 105 kg/m2
(100 psi).

          Direct shear testing was performed by Dravo on un-
stabilized  FGD sludges to compare effects of stabilization.
The untreated sludge exhibited an angle of internal friction
between 27  and 30° (Ref. 56).  Strengths were found comparable
to that of medium dense sand.

          The thixotropic nature of sludge with high sulfite
content poses some difficulty with respect to load-bearing
properties.  Dewatered Shawnee sludge (50 percent solids) was
placed in an open-air, drained pit 2.4 x 2.4 x 0.3 meters and
allowed to  dewater naturally for 30 days.   At the end of this
time the solids content was 36 percent solids and the sludge
appeared firm;  large cracks were evident on the surface.  A
load of 2400 ,,kg/m2 (500 lb/ft2) (minimum for recreational
purposes) was placed on a 1.2 meter (4 foot) square section of
surface.   After 10 days no settling had occurred.  However,
the solids  fluidized and lost all bearing strength when vibrated
with a concrete vibrator (Ref.  58)

          Due to the nature of scrubber wastes produced by
lime/limestone systems, settling is not expected to result in
                               105

-------
extensive separations.  From a bench-scale experiment conducted
by TVA, a settling rate of 5 cm/hr (12.7 in./hr) was observed
for the first and second phases of settling, which were defined
as the induction period during which floe formation occurs and
the second stage, free settling (Ref. 57).  The third phase is
compression settling; i.e., when the floes begin to touch each
other and gel formation occurs.  The settling rate during this
stage was greatly reduced.  After 48 hours the settling rate de-
creased to practically zero and no further settling was observed,
even over a period of several months.

          Aerospace reported that limestone sludges with high sul-
fate content settle to 45 percent solids with no drainage provided,
This is compared to final settled solids content of 50 percent
with underdrainage.   Sludges with high sulfite content were
found to settle only to 35 percent solids regardless of whether
drainage was provided (Ref. 51).  The presence of fly ash will
generally improve settling of high sulfite sludges (cf.  30 - 35
percent for low fly ash and 35 - 40 percent solids for high fly
ash) (Ref.  59).  For specific sludges, Shawnee samples settled
to 45 percent solids and drained freely to 52 percent; Mohave
sludge, a high sulfate type, reached 67 percent solids regard-
less of whether drainage was provided.  Percentages of sulfite
oxidation for the two samples were reported to be 20 - 25 per-
cent and 75 percent, respectively (Ref. 51).  In investigating
the effects of underdrainage on the drainage rate in bench-
scale column studies, the steady-state drainage rate for wet
Shawnee sludge was reported to be 0.046 cm3/min.  when sludge
was allowed to air dry in the columns, several days were
required for initiation of drainage again; the drainage rate
was then much less than that observed for wet sludge.  Eventually,
enough water was retained by the sludge column to return it to
its original water content (51.7 percent).
                             106

-------
          Dravo Corporation compared solid contents of various
 power plant waste  after one day of settling.  Identities
 of  samples for which data are presented below were given in
 Table 1-24 (Ref. 55).
             Sludge Source               Wt Percent Solids

    Eastern Coal Sludge  (with ash)            <30-45
    Western Coal Sludge  (no ash)                21.5
    Dry Injected/Wet Scrubber Sludge
       (with ash)                                24
    Limestone Scrubbing Sludge
       (no ash)                                  39
    Smelter Gas Sludge (no ash)                37-40
    Fly Ash                                     64
          Figure 1-6 presents results of a settling test for
an FGD sludge, presumably from an Eastern coal-fired, lime
scrubbed utility.  The sample tested contained 35 grams of
solids per liter.  These results indicate that essentially all
of the settling occurs within the first 60 minutes with little
further settling afterwards (Ref. 56, 60).

          Settling characteristics of lime/limestone scrubbing
sludges are directly related to the degree of compaction.  The
factors affecting this parameter include.the following, all of
which are under investigation by TVA (Ref. 57):
                             107

-------
C/)
0)
,£
u
M
•H
01
PC
                                35  GM Solids/Liter
         10 20 30  40  50 60 70 80 90 100 110 120 130 140 150 160 T70 180 190 200


                                  Time,  Minutes
       Figure 1-6.  Settling  Test for Untreated  FGD Sludge

                             (Ref.  56).
                                108

-------
           1.   Hydraulic head.

           2.   Ash content.

           3.   Degree of oxidation (percentage  of
               CaSO^-2H20).

           4.   Stirring.

           5.   Agglomeration .

           6.   Lime versus limestone.

           Results of bench-scale  studies indicate that increas-
ing the height of the slurry column increases degree of compaction.
When the height of an experimental column was increased from 13
cm to 100  cm  (5.1 to 39.4 inches) compaction was increased by
15 percent.

          The influence of ash content on settling characteristics
of scrubber sludge is not completely characterized.   However, it
is predicted that a high ash content in the sludge would improve
settling although no data are available to support this point.
This type of information could bear on the decision to dispose
of scrubber sludge and fly ash together or separately.

          Degree of oxidation is under intensive study.  It is
known that calcium sulfate (gypsum) crystals,  because of their
large blocky nature,  settle better than the thin plate-like
calcium sulfite hemihydrate crystals.   Thus,  oxidation to
sulfate should improve the degree of compaction.  It has been
                              10Q

-------
reported that a high degree of oxidation is required, however,
to produce a noticeable effect.  Methods under study to promote
oxidation of limestone scrubber slurries include:

          1.  Air introduction into the scrubber.

          2.  Oxidation in separate unit; e.g.,
              scrubber effluent hold tank.

          3.  Spinning cup oxidizer .

          4.  Use of catalysts.

          Technology developed in Japan involves the use of
a spinning cup oxidizer (rotary atomizer) treating low pH (3.5 -
4.0) slurry and is considered to be a commercially demonstrated
process to produce a high quality gypsum product (Ref. 61, 62).
Another oxidation process applied involves catalytic oxidation
of the sulfite and S02 by further contact with flue gas and
air.  The catalyst is recycled by precipitation as the hydroxide.

          Identification of scrubber conditions which promote
agglomeration of sulfite crystals has not been made yet.   Some
sulfite crystal agglomeration has been noted.   Flocculating
agents are being investigated to determine their effectiveness
in promoting appreciable agglomeration.  The type of limestone
and the particle size may also influence settling characteristics
of the sludge.

          An interesting general observation reported by Crowe
was that sludges composed entirely of either calcium sulfite,
                               110

-------
fly ash, or calcium carbonate dewater readily and are relatively
stable after dewatering (Ref.  58).   However,  mixtures of these
three types exhibit poor dewatering and compaction qualities.
It was suggested that the calcium carbonate somehow contributes
to the poor settling characteristics of some sludges.
                            Ill

-------
F.        REFERENCES

1.        Dupree, Walter, G., Jr. and James A. West, U. S.
          Energy through the Year 2000. Washington, U. S. Depart-
          ment of the Interior, 1972.

2.        Swabb, L. E., "Fuel Oil Desulfurization," in Sulfur in
          Utility Fuels:  The Growing Dilemma.  Proceedings of
          Electrical World Technical Conference, Chicago,
          Oct. 25-26. 1972. N.Y., McGraw-Hill, 1972.

3-        Kett, Terence K., Gerard C. Lahn, and Wm. L. Schuette,
          "Resid Conversion Route," Chem. Eng. 81  (27), 40
          (1974).

4.        Raben, I. A., "Status of Technology of Commercially
          Offered Lime and Limestone Flue Gas Desulfurization
          Systems," presented at the Flue Gas Desulfurization
          Symposium, New Orleans, La., May 14-17, 1973, San
          Francisco, Ca.,  Bechtel Corporation, 1973.

5-        Epstein,  M., et al.,  "Limestone and Lime Test Results
          at the EPA Alkali Scrubbing Test Facility at the TVA
          Shawnee Power Plant," presented at the Flue Gas De-
          sulfurization Symposium,  Atlanta,. Ga.,  Nov.  1974,
          San Francisco, Ca., Bechtel Corp.,  1974.

6-        Van Ness,  Robert P.,  "Operational Status and Per-
          formance  of the  Louisville FGD System at the Paddy's
          Run Station,"  presented at the Flue Gas Desulfurization
          Symposium, Atlanta, Ga.,  1974, Louisville Gas &
          Electric  Co.,  1974.
                              112

-------
 7.        Erdman, Donald A., "Mag-Ox Scrubbing Experience at
          the Coal-Fired Dickerson Station,Potomac Electric
          Power Company," presented at the Flue Gas Desulfuriza-
          tion Symposium, Atlanta, Ga.,  Nov. 1974, Washington,
          B.C. Potomac Electric Power Co., 1974.

 8.        Quigley, Christopher P. and James A. Burns,
          "Assessment of Prototype Operation and Future
          Expansion Study - Magnesia Scrubbing Mystic Generating
          Station," presented at the Flue Gas Desulfurization
          Symposium, Atlanta, Ga., 1974,  Boston, Mass., Boston
          Edison Co.,  1974.

 9.        Phillips, Robert J.,  Sulfur Dioxide Emission Control
          for Industrial Power Plants, Warren, Michigan, General
          Motors Technical Center, 1971.

 10.       Bresler, Sidney A. and John D.  Ireland,  "Substitute
          Natural Gas:  Processes, Equipment, Costs," Chem.
          Eng.  79 (23),  94 (1972).

 11-   .    U.  S.  Department of the Interior, Office of Coal
          Research, Clean Energy from Coal - A National Priority.
          1973 Annual  Report, Washington,  D.C.,  pp.  19-42 (1973).

12.       Curran,  G. P.,  C.  E.  Fink,  and  E. Gorin, "Production
          of  Low Sulfur  Boiler  Fuel by Two-Stage Combustion -
          Application  of C02 Acceptor Process,"  Proceedings
          of  the Second  International Conference on Fluidized-
          Bed Combustion.  October 4-7,  1970,  pp.  III-l-l to -12,
          PB  214-750 (AP-109),  EPA,  Research Triangle Park,
          N.C.
                              113

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13.        National Economic Research Associates,  Inc.,  Fuels
          for the Electric Utility Industry,  1971-1985. New
          York,  Edison Electric Inst.,  1972.

14.        "FPC Fuel Reports:   Plant-by-Plant  Deliveries of
          Major Fuels to Utilities in April and May," Electrical
          Week,  August 1974.

15.        U.  S.  Bureau of Mines,  Sulfur Reduction Potential
          of the Coals of the United States,  1972.   Report No.
          128.23:7633 (USBM Report RI 7633, EPA Report APTD-
          1365).

16.        Bituminous Coal Research, An Evaluation of Coal
          Cleaning Processes and Techniques for Removing
          Pyritic Sulfur from Fine Coal, April 1971, PB 205-
          185 (APTD-0842).

17.        Weir,  Paul, An Economic Feasibility Study of Coal
          Desulfurization, October, 1965, PB 176-845 (APTD-1245).

18.        Hamersma, J. W., et al., TRW, Chemical Desulfurization
          of Coal:  Report of Bench Scale Developments, February,
          1973,  2 volumes, PB 221-405 and -406 (EPA-R2-73-173a and b)

19.        McGlamery, G. G. and R. L. Torstrick, "Cost Comparisons
          of Flue Gas Desulfurization Systems," presented at
          the Flue Gas Desulfurization Symposium, Atlanta, Ga.,
          Nov. 1974, Muscle Shoals, Ala., TVA, 1974.

20.        Archer, D. H., et al., Westinghouse, Evaluation of
          the Fluidized Bed Combustion Process, Volume I,
          November 14, 1971, PB 211-494  (APTD-1165).
                              114

-------
21.       National Research Council, Div. of Engineering, Ad
          Hoc Panel on Evaluation of Coal Gasification Tech-
          nology, Evaluation of Coal-Gasification Technology,
          Part 1^.  (COPAC-6) , Pipeline Quality Gas, Washington,
          D.C.

22.       (M. W.) Kellogg Co.,  Economic Summary and Comparison
          of Flue Gas Desulfurization,  Solvent Refined Coal,
          and Low Btu Gas as_ Applied t£ Conventional Steam
          Power Plants. Houston, Tx.,  1974.

23.       Sulfur Oxide Control Technology Assessment Panel
          (SOCTAP),  Final Report on Projected Utilization of
          Stack Gas Cleaning Systems by_ Steam-Electric Plants,
          April 1973, PB 221-356 (APTD 1569).

24.       Gage, S. J.,  Technological Alternatives t£ Flue Gas
          Desulfurization,  presented at the Flue Gas Desulfuriza-
          tion Symposium, New Orleans,  La., May 14-17, 1973.

25.       Radian Corp., Factors Affecting Ability t£ Retrofit
          Flue Gas Desulfurization Systems, PB 232-376/AS
          (EPA-450/3-74-015),  Austin.  Tx.. 1973.

26.       (M. W.) Kellogg Co.,  "Applicability of S02 Control
          Processes  to Power Plants,"  PB 213-421 (EPA-R2-72-100),
          Piscataway, N.J., 1972.

27.       "Sulfur Dioxide Removal Systems," Mcllvaine Wet
          Scrubber Newsletter 1974 (4),  3.

28.       Bucy, J. I. and P. A.  Corrigan, "TVA-EPA Study of
          the Marketability of  Abatement Sulfur Products,"
                              115

-------
          presented  at  the Flue Gas Desulfurization Symposium,
          Atlanta, Ga., Nov.  1974, Muscle Shoals, Ala., TVA,
          1974.

29.       National Coal Association, Steam-Electric Plant
          Factors. 1972 Edition, Washington, D.C.

30.       EPA, Report of the  Hearing Panel, National Public
          Hearings on Power Plant Compliance with Sulfur Oxide
          Air Pollution Regulations. Washington, D.C., January,
          1974.

31.       Dunkak, John, "Control of Scaling in Calcium Sulfite
          Digester Heat Exchangers," TAPPI 45(4), 196A-198A
          (1962).

32.       Radian Corp., Evaluation of Lime/Limestone Sludge
          Disposal Options. PB 232-022/AS (EPA-450/3-74-016),
          Austin, Tx  . 1973

33.       Council on Environmental Quality,  Energy and the
          Environment:  Electric Power,  August, 1973.

34.       Young,  L.  B.,  "Forests of the Future," Sierra Club
          Bulletin,  Volume 58, Number 8, September,  1973.

35.       Shomaker,  Norbert,  ORD,  NERC-Cincinnati,  SHWRL,
          Disposal Technology Branch,  personal communication,
          August  1973,

36.       U.  S. Dept. of the  Interior,  Bureau of Mines,  Methods
          and Costs  of Coal Refuse Disposal  and Reclamation.
          1C  8576,  Pittsburgh, Pa.,  1973.
                              116

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37.       U. S. Department of the Interior,  Bureau of Mines,
          Minerals Yearbook 1970, Vol.  I, Metals,  Minerals,
          and Fuels, Pittsburgh, Pa., 1972.

38.       Rohrman, F. A.,  "Analyzing the Effect of Fly Ash on
          Water Pollution," Power 115 (8), 76-7 (1971).

39.       Environmental Protection Agency, Task Force for
          Sewage Sludge Incineration, Sewage Sludge Incineration,
          EPA-R2-72-040,  Washington, D.C., 1972.

40.       Battelle Memorial Institute,  Inorganic Fertilizer
          and Phosphate Mining Industries—Water Pollution and
          Control. Columbus, Ohio, 1971, Washington, G.P.O.,
          1971.

41.       Hill, Ronald, ORD, NERC-Cincinnati, Mine Drainage
          Pollution Control Activities,  personal communication,
          August 1973.

42.       Lovell, Harold L., "The Control and Properties of
          Sludge Produced from the Treatment of Coal Mine
          Drainage Water by Neutralization Processes," in Coal
          Mine Drainage Research.  Preprints of Papers Presented
          before the Third Symposium, Pittsburgh,  Pa., 1970,
          pp. Iff.

43.       Stowasser, W. F., Bureau of Mines, Div.  of Nonmetallic
          Minerals, personal communication,  August 1973.

44.       Reserve Mining Co. ,  Report to^ the Minnesota Pollution
          Control Agency for the Month of August,  1971, Silver
          Bay,  Minnesota,  1971.
                              117

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 45.        Ifeadi,  C.  N.  and H.  S.  Rosenberg,  "Lime/Limestone
           Sludge  Disposal  - Trends in  the  Utility  Industry,"
           presented  at  the Flue Gas  Desulfurization  Symposium,
           Atlanta, Ga.,  Nov.  1974,  Columbus,  Ohio, Battelle -
           Columbus Labs.,  1974.

 46.        Lord, William  H.,  presentation at Waste Disposal in
           Utility Environmental  Systems Conference,  Chicago, 111.,
           Oct. 29-31, 1973,  Pittsburgh, Pa.,  Dravo Corp., 1973.

 47.        Rossoff, J., R.  C.  Rossi and J. Meltzer, "Study of
           Disposal and Utilization of By-products from Throwaway
           Desulfurization  Processes," presented at the Flue Gas
           Desulfurization  Symposium, New Orleans, La., May 14-17,
           1973.

 48.        Coal Utilization Symposium - Focus  on S02  Emission
           Control. Louisville. Ky_., October.  1974, Proceedings.
           Monroeville, Pa.,  Bituminous Coal Research, 1974.

 49.        Schmitt, C. R.,  Survey of the Fly Ash Disposal System
           at the Oak Ridge  Y-12 Plant.  Y-1713, Oak Ridge, Tenn.,
           1970.

 50.        Tennessee Valley Authority, Review of Waste Water
           Control Systems,   Widows Creek Steam Plant, Muscle
           Shoals, Alabama,   1971.

51.       Rossoff, J.  and R. C.  Rossi,  Disposal of By-products
          from Nonregenerable Flue Gas  Desulfurization Systems:
          Initial Report, PB 237-114/AS (EPA-650/2-74-037-a),
          El Segundo,  Ca.,  Aerospace Corp.,  1974.
                               118

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52.       Rossoff, J. et al., "Disposal of By-products from
          Nonregenerable Flue Gas Desulfurization Systems,"
          presented at the Flue Gas Desulfurization Symposium,
          Atlanta, Ga.,  Nov. 1974, El Segundo,  Ca., The Aerospace
          Corp., 1974.

53.       RI7260, Chlorine in Coal Combustion,  Bureau of Mines,
          May 1969.

54.       ORNL-NSF-EP-43, Trace Element Measurements at the
          Coal-Fired Allen Steam Plant, Oak Ridge National
          Laboratory, March 1973.

55.       Selmeczi, Joseph G. and R.  Gordon Knight, "Properties
          of Power Plant Waste Sludges," Paper  #B-7, presented
          at Third International Ash Utilization Symposium,
          Pittsburgh, Pa., March 13-14, 1973.

56.       Lord,  William  H.,  "FGD Sludge Fixation and Disposal,"
          presented at the Flue Gas Desulfurization Symposium,
          Atlanta, Ga.,  Nov. 1974, Pittsburgh,  Pa., Dravo Corp.,
          1974.

57.       Slack, A. V. and J. M.  Potts, "Disposal and Use of
          By-products from Flue Gas Desulfurization Processes
          Introduction and Overview," presented at the Flue Gas
          Desulfurization Symposium,  New Orleans, La., May 14-17,
          1973.

58.       Crowe, James L., "Sludge Disposal from Lime/Limestone
          Scrubbing Processes," Preprint 2354,  presented at the
          ASCE Annual and National Environmental Engineering
          Convention, Kansas City, Mo., Oct.  1974.
                               119

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59.       Jones, Julian W., "Environmentally Acceptable Disposal
          of Flue Gas Desulfurization Sludges:  The EPA Research
          and Development Program," presented at the Flue Gas
          Desulfurization Symposium, Atlanta, Ga., Nov. 1974,
          Research Triangle Park, N.C., EPA, Control Systems
          Lab., 1974.

60.       Lord, William H,, Dravo Corp., private communication,
          Feb. 26, 1974.

61.       Ando, Jumpei,  "Status of Flue Gas Desulfurization
          Technology in Japan," presented at the Symposium on
          Flue Gas Desulfurization, Atlanta, Ga.,  Nov.  1974,
          Kasuga,  Bunkyo-Ku,  Tokyo, Chuo Univ.,  1974.

62        Ando, Jumpei,  "Utilizing and Depositing  of Sulfur
          Products from Flue  Gas Desulfurization Processes
          in Japan," presented at the Symposium  on Flue Gas
          Desulfurization, Atlanta, Ga., Nov.  1974,  Kasuga,
          Bunkyo-Ku, Tokyo, Chuo Univ.,  1974.
                               120

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                II.  APPROACHES TO DISPOSING OF
            OR UTILIZING SCRUBBER SLUDGE MATERIALS

          Several alternatives are available for disposition
of waste material generated by lime/limestone scrubbers.  They
include commercial utilization, ponding of untreated sludge,
and landfilling of treated and untreated material.  Other pos-
sibilities which have not received much attention thus far are
deep mine disposal and deep well injection.

          Ponding and landfilling are the chief methods used
by the utility industry to dispose of ash from fuel combustion.
Most technology available to date is based on experience with
that material.  Technology associated specifically with sludge
is just now being demonstrated.  The following sections discuss
commercial utilization, describe various features of each dis-
posal operation and, on the basis of available data, present
the potential impact on water pollution and land use.

A.        COMMERCIAL UTILIZATION

1.0       Overview

          Considerable research has been performed to determine
the technical properties and characteristics of the potential
commercial products of sludge.  As a result, numerous products
and applications have been developed, some of which would require
the consumption of a major portion of the available sludge if
used on a large scale on a national basis.   However, to do so
would require that these new products successfully compete
both technically and economically on the open market with well
established manufactured or natural products.   With sludge
being a relatively new material not yet available in large
                              121

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quantities throughout the nation, a true test of the market
has not been made.  However, indications are that the potential
sludge products will not compete well enough in the near term
to consume an appreciable portion of the projected supply and
that the principal concern for sludge will be disposal and not
utilization.

2.0       Technical State-of-the-Art

          2.1  Potential Utilization

          Research, development, and investigative activities
have been conducted concerning the potential utilization of
power plant desulfurization sludges by numerous government and
private organizations.  Some of the more significant of these
include the EPA (Refs. 1, 2, 3), the Bureau of Mines (Ref. 4),
the Federal Highway Administration (Ref. 5), West Virginia
University's Coal Research Bureau (Refs. 1, 2, 6), the TVA
(Ref. 7), the Aerospace Corporation (Ref. 3), Combustion Engineer-
ing, Inc. (Ref. 8), I.U. Conversion Systems, Inc. (Refs. 9-12),
the National Ash Association (Ref. 13), and Dravo Corporation
(Ref. 14).  These efforts have identified sludge as a unique
raw material which has some potential use in the manufacture of
products now using fly ash as an additive, or in new products
or applications.

          An inspection of the listing of products for which fly
ash is used as an additive, and the applicability of the sludges
to these products, provides an insight into the great difficulty
attached to the possible utilization of the throwaway sludge.
For example, an annual survey conducted by the Edison Electric
Institute (Ref. 13) presents a breakdown of ash collection and
utilization in the United States for the year 1971.  This
                              122

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breakdown  is given in Table II-l.  Several significant factors
relevant to sludge utilization can be derived from the chart
and previous EEI surveys  (Ref. 3); (1) a low percentage of the
available  fly ash actually used;  (2) some technical capability
but an economic inability to apply sludge in most uses of fly
ash; and (3) the economic inability to apply sludge in the major
use of bottom ash and boiler slag; e.g., fill material for roads.

           In Table II-l, it is shown that 5 percent of all fly
ash produced was utilized in the products noted, and that another
6.7 percent was removed from plant sites at no cost to the
utility (some was used and the remainder was probably stored).
In addition, there is the utilization of bottom ash and boiler
slag, principally as a constructional fill material with which
the sludges cannot compete economically because the bottom ash
and slag are used as aggregate without appreciable processing
while sludge must be chemically treated (fixed) before it can
be used for this purpose.   When all these applications for power
plant ash are considered,  the maximum utilization is about 20
percent of the total quantity produced.   Of these applications,
the "stabilizer for road bases, parking areas, etc." category
is the only current use in which the sludge should be able to
compete in the ash market from a technical and economic stand-
point.   As an artificial aggregate, it can also enter some local
markets depending on the supply of natural aggregate.   However,
the current ash-usage categories of "road bases" and "aggregate"
account for a usage of less than 1 percent of the total ash
produced.   Also,  it has been shown that for a given power plant,
an alkali scrubber system will produce a sludge (including ash,
dry basis)  quantity approximately twice the quantity of the ash
produced without scrubbing (Ref.  15).   Therefore,  with the by-
product production increased as much as  2 times at a given plant,
and the potential utilization in the near term being inconsequential
                              123

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         Table II-l.   ASH COLLECTION AND UTILIZATION YEAR 1971
                             a
                                   Fly Ash
                                    Tons
             Bottom Ash
                Tons
            Boiler Slag
            (if Separated
            from Bottom
            Ash)  Tons
 1.   Ash utilized

     a.   Mixed with raw material
         before forming cement
         clinker

     b.   Mixed with cement
         clinker or mixed with
         cement (pozzolan cement)
     c.   Partial replacement  of
         cement in:
         1.   Concrete  products
         2.   Structural concrete
         3.   Dams and  other mass
             concrete

     d.   Lightweight aggregate
     e.   Fill  material  for roads,
         construction  sites,  etc.
     f.   Stabilizer  for road
         bases,  parking areas,
         etc.

     g.   Filler  in asphalt mix
     h.   Miscellaneous

           Total Item  1
                       9
2.   Ash  removed from plant site
     at no cost  to utility but
    not  covered in categories
     listed under Item  1.

3.  Total ash utilized

4.  Ash  removed to disposal
    areas at  company expense

5.  Total ash collected

6.  Estimated 1976 ash
    production
    104,222


     16,536
    177,166
    185,467

     71,411
    178,895

    363,385
    36,939
   147,655
    98,802
 1,872,728
 3,253,206


24,497.848
               91,975
   35,377      76,563
   13,942

  533,682  2,628,885


    7,880     49,564
    2,833     81,700
  475.417    428T026
 1,380,478    1,069,131  3,356,713
  542.895    381.775
1,612,026  3,738,488


8,446.941  1.232.298
27,751.054   10,058.967  4.970.786
36.994.436  117,411,603  2.517.703
aRef.  13
                                  124

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on a national basis, the disposal of the by-product appears to
be the principal method for handling these materials.

          2.2  Effect of Material Properties

          Chemical analyses of various sludges are presented
in Table II-2.  The compositions can be seen to vary widely
with such things as the sulfur and ash contents of the coal
burned and the methods of S02 and particulate collection.  As
a result, the physical properties also vary from sludge to
sludge.  Not only are the variations in properties great, but
the differences when compared to regular fly ash are considerable

          The principal problems that face the utilization of
the sludge are, therefore, centered in several areas:  (1) the
quality of the sludge is affected appreciably by the sulfur
content of the coal burned, and by the efficiency of the com-
bustion and scrubbing process; (2) the sludge contains sulfur
which creates additional problems of sulfur gas evolution for
manufacturing processes employing high temperatures; (3) the
pozzolanic (concreting) properties of the sludge are weak when
compared to those of fly ash; and (4) the volume of sludge
produced will be much greater than that of the ash produced
without the scrubbing process.

          On the positive side, as appropriate, the sludge
contains:  (1) some pozzolanic properties, (2) nominal amounts
of unreacted alkali, and (3) appreciable amounts of gypsum.

          Another point to consider is the collection of fly
ash in the scrubber.  At power plants where efficient fly ash
collection systems exist, the fly ash is collected upstream of
the scrubber.  In those cases, very little fly ash exists in
the sludge and, for essentially all developments for sludge
                              125

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                                         Table II-2. '  CHARACTERISTICS OF SLUDGE FROM OPERATING SO. SCRUBBERS
Facility
Laurence 4
Lawrence 5
Hawthorn 3
Hawthorn 4
Will County 1
Stock Island

La Cygne
Cholla

Paddy's Run 6

Mohave 2

Sulfur Content Ash Content Method of
of Coal of Coal Participate
wt percent wt percent Control
3.8
3.3
3.0
3.0
3.5
2.0

5.3
0.5

3.7

0.4

12
12
13
13
15
0.04

22
10

14

10

Marble bed
Marble bed
Marble bed
Marble bed
Venturi
Mechanical
collector
Venturi
Flooded disc
scrubber
Electrostatic
precipitator
Electrostatic
precipitator
Method of Rate (dry basis),
S02 Control metric tons/hr
Limestone
Limestone
Limestone
Limestone
Limestone
Limestone

Limestone
Limestone

injection
injection
injection
scrubbing
scrubbing
scrubbing

scrubbing
scrubbing

Lime scrubbing


Lime scrubbing


10.7
34.4
12.4
15.4
17.5b
2.4

12.5
3.1

5.3

1.5b

Sludge Composition (dry basis), wt percent
CaS03-l/2H20 CaSOA'2H20 CaC03 Fly Ash
10
10
20
17
50
20

40
15

94

2

40
40
25
23
15
5

15
20

2

95

5
5
5
15
20
74

30
0

0

0

45
45
50
45
15
lc

15
65

4

3

Estimated
Solids Content
of Dewatered Sludg
wt percent
50
50
40
40
35
50

35
50

40

65

 Ref.  16
 Prior to stabilization
 Mainly unbumed  carbon
NJ

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usage other than gypsum production, fly ash will have to be
added to provide the pozzolanic properties necessary for
structural qualities.

          2.3  Potential Product Applications

          Technical developments for the potential usage of
the sludge have been made for the most part by:  the Coal
Research Bureau at the University of West Virginia under the
sponsorship of the EPA; the G&WH Corson Company (now IUCS)
near Philadelphia, Pennsylvania; and Combustion Engineering,
Windsor, Connecticut.  Uses being studied or considered include
those for which fly ash is being used or could be used, plus
new developments.   The following lists provide a summary of
those considerations, and include uses that may be possible
regardless of how slight their potential is.  The first category
presents applications in which fly ash has been used:

          1.   Concrete admixture (structure and
              products).

          2.   Manufacture of Portland cement.

          3.   Fired brick.

          4.   Filler in bituminous concrete.

          5.   Road base course,  parking lots,  etc.

          6.   Structural fill.

          7.   Soil amendment.
                              127

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sludge:
          8.  Mine void fill.

          9.  Neutralization of acid mine drainage.

          The second category includes potential new uses for
          1.  Autoclaved products - gas concrete,
              bricks, mineral aggregate.

          2.  Hot press sintering - pipes, metal
              coatings.

          3.  Gypsum products - wallboard, plaster.

          4.  Mineral recovery.

          5.  Sulfur or sulfuric acid production.

          6.  Artificial aggregate.

          2.4  Use-Inhibitions

          The difficulty associated with the small usage of
fly ash in the United States and the weak projections for the
potential use of sludge products are best seen by examining
the inhibitions to the use of fly ash and the comparison of fly
ash properties with those of the sludge.  It has been determined
that the major inhibitions to the use of fly ash, which generally
apply to the inhibitions to the use of sludges, are:

          1.  Highly variable chemical and
              physical properties.
                              128

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           2.  Lack of  control or availability of
              usable supply when needed.

           3.  Necessity for appreciable capital
              expenditures to classify, handle,
              store, or process materials.

           4.  High transportation costs.

           5.  Inability to economically compete
              with other materials.

           Although it has been shown that there are many uses
for the fly ash, considering already developed technologies,
and that these potential products are in many ways equal or
superior to existing materials (Ref. 3), its actual utilization
has been limited.  The situation is not improved for FGD sludge,
as described in the following discussion.

           Relating the potential technical uses of the sludge
to the basic properties and qualities previously mentioned in
Subsections 2.2 and 2.3, various factors are applicable regard-
ing the potential utilization of large tonnages of sludge on a
national basis.   These factors identify reasons wherein the
sludge product is expected to be technically or economically
inferior to a fly ash product (which is already in a weak
marketing position as shown in Table II-l),  where its production
or use may create a pollution problem,  or where it may be tech-
nically sound but not economically competitive on a wide scale.
These factors are:

           1.  The sludge is produced in a wet.
              state and will have to be dewatered
              or dried for many uses to prevent
                              129

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    agglomeration due to the interaction
    of the pozzolan with self-contained
    lime in the presence of water.  Ag-
    glomeration can require a grinding
    operation depending on fineness required
    for structured concrete qualities.

2.  Its pozzolanic properties for concrete
    product applications are reduced because
    the fly ash content and consequently the
    glassy phase is reduced.

3.  Sludge properties can be highly variable;
    therefore, blending may be required for
    many applications.

4.  The use of sludge in the manufacture of
    sintered products has three distinct
    disadvantages:

    a.  Sulfur is released and would have
        to be collected.

    b.  Decomposition of sulfates (or
        sulfites) takes place at tempera-
        tures below sintering and results
        in the physical destruction of the
        "green formed"  product.

    c.  The fusion temperature is such
        that a short range exists between
        sintering and melting, thereby
        requiring a sophisticated tempera-
                \
        ture control system for the sinter-
        ing process.
                     130

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           5.  The  soluble  salt content of the sludge
              presents a potential problem of leach-
              ing  heavy metals to groundwaters for
              certain applications such as soil amend-
              ment and acid mine drainage neutralization.

           6.  The  technology for mineral recovery to
              obtain aluminum  (Ref. 1), iron, titanium,
              silicon, and lime is undeveloped or
              very costly.

           7.  Severe competition exists from a satu-
              rated current market for products such
              as gypsum,* mineral wool  (Ref. 3),  sulfur,
              and  sulfuric acid  (Refs. 3, 8).

           8.  High capital investments are necessary
              to produce autoclave products.

           In consideration of the factors noted,  it should be
recognized that of all the potential large scale uses for sludge,
the most promising are:   (1)  road base materials (Refs. 5, 6,
10, 12) and artificial aggregate (Ref. 9), and (2) landfill or
land reclamation when appropriately conditioned to prevent
leaching (Refs.  8,  9,  11, 13).   The former are considered com-
mercial utilizations of the sludge while the latter is generally
considered a disposal process.   As a road building material,
sludge has a potential for large tonnage utilization;  however,
 The only sludge product sold overseas is gypsum which is
marketed in Japan where the material is competitive (Refs. 4,
17).  It is projected that in Japan in the mid-1970's, the
sludge-gypsum supply will exceed demand (Ref. 4).
                              131

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 it must compete with existing materials such as crushed rock
 and bituminous concrete  (Ref. 3).  Although the sludge-produced
 road base materials are believed crack resistant when compared
 to competing products, crushed rock in particular is acceptable
 by most specifications and agencies and is less expensive.  Only
 in local areas where rock is not available or allowed would
 sludge materials have a ready market.  Artificial aggregate
 could also consume large masses of the sludge, but its demand
 is only local where natural aggregate is not available.  In the
                       i
 near term, this is not expected to be a widespread condition.

          In summary, because scrubber sludge is not expected
 to find large scale commercial outlets in the near term, it is
 concluded that the major consideration must be disposal.  Al-
 though utilization is desirable in the long run, near term
 treatment/disposal solutions must occupy a higher priority.

 B.        PRESENT AND PLANNED UTILITY INDUSTRY DISPOSAL PROGRAMS

          Sludge disposal is a problem to a portion of the
 utility industry regardless of whether or not it presents a
pollution problem because of quantities of materials that must
be handled and disposed of.   Utilities currently operating or
planning installation of a lime/limestone scrubbing system must
 consider many factors such as:

          Nonuniform environmental standards
          invoked by local regulatory agencies.

          Variations in sludge chemical and
          physical properties  resulting from
                            132

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          varying properties of process ingre-
          dients  (coal, sorbent, water); varia-
          tions in types of ash collection and
          scrubbing processes.

          Disposal site location and ownership;
          sites not owned by the utility
          company generally require more strin-
          gent treatment.

          Disposal site geotechnical and meteoro-
          logical factors; proximity to ground
          and surface waters, topography, soil
          permeability, and rainfall/evaporation.

          These factors (not necessarily a complete list),
which affect the technique and cost of sludge disposal, indicate
that no single solution may be applicable to all sludge disposal
situations.   As a result, utility companies have taken different
approaches toward solution of their site-specific disposal
problem.

          Table II-3 summarizes the dewatering and final mode
of sludge disposal that utilities have selected for specific
lime/limestone installations.   As can be noted,  ponding tech-
niques outnumber landfill disposal approaches by about a 3:2
ratio.  Brief notes on selected installations representing
specific disposal approaches follow:
                               133

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                     Table II-3.  SLUDGE TREATMENT/DISPOSAL TECHNIQUES  FOR SELECTED UTILITY LIME/LIMESTONE  FGD SYSTEMS
                                              (C = Current; P = Possible Additions)
         Facility
         (Availability
           Status)

         TVA-Shawnee
           (Current)
                   Sorbent
                                                  Scale
                                             Eastern
                                             coal
          Clari-
           fier
                                                                   Dewatering  Technique
Filter
Centri-
 fuge
                                                                                     Dryer
                                            Pond
                                                        Final  Disposition
                                  Ponding
                                                                                                             (Unlined)
Landfill
         City of Key
         Vest-Stock
         Island
           (Current)
                   Lixestone
                   (coral marl)
         CcrTOnwealth
         Edison Co.-Will
         County
            (Current)
                                    Residual
                                    oil
                                                 Full
                                                                (Unfixed)
                   Limestone
                                    Eastern
                                    coal
                                                 Full
                                           (Clay
                                           lined,
                                           well
                                           Points)
                                                C
                                             (Fixed)
LO
         California
         Ed i s on-Mohave
         Li-re:  Current
         Li-estone: Oct
                   Limestone
                   & lime
                                                 Full
                                    Western
                                    coal
                                                                                                       C
                                                                                                    (Fixed)
         Kd-.sas City
         Pc->sr L Light-
         Kawchorn
            (Current)
                   Boiler
                   injected
                   limestone
Full
                            Boiler
                            injected
                            li~estone
                                             Coal
                                         (possible E&W
                                         blend)	
                                                                                              C
                                                                                            (Well
                                                                                            points)
                                                   (Unlined)
Kc-.£as Power
Ligrc -
Lavreice
  (Current)
         Louisville Gas
         L Electric
         Paddy's Run

           (Current)
                                             Eastern
                                             coal
Full
                                                      C
                                                   (Unlined)
                   Carbide
                   sludge
                   (Ca(OH)2)
Full
                                             Eastern
                                             coal

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               Table II-3 (Continued). SLUDGE TREATMENT/DISPOSAL TECHNIQUES FOR SELECTED UTILITY LIME/LIMESTONE FGD SYSTE>S

                                                (C= Current; P = Possible Additions)
 Facility
 (Availability
  Status)

Northern States
Power - Black
Dog (Current)
Sorbent
                    Fuel
Linestone
                    Western
                    coal
                                Scale
                               Pilot
Clari-
 fier
         Dewatering Technique
                                                                           Filter
Centri-
  fuge
Dryer   Pond
                                                                                                                Final Disposition
Ponding
                                                                                   (Unlined)
Landfill
V-'snsas City Power
'& Light - LaCygne
(Current)
Limestone
                                Full
                    Eastern
                    coal
                                          (Unlined)
Anzor-.a Public
Service -
Chclla
.'Current)
Limestone
                                Full
                    Wes tern
                    coal
                                          (Unlined)
                                          (Solar
                                           evap)
to     Ducuesne Light
Ui     ^hillips
       (C-jrrep.t)
                   Lime
                                                   Full
                                        Eastern
                                        coal	
                                                                           C
                                                                        (Curing)
                                                                        (Unlined)
                                                        C
                                                     (Fixed)
Eetrcic
Idis DP -
St. Clair
(.Jan. 1975)
Limestone
                                Full
                     Eastern
                     coal
                                                                                              (Unfixed)
T\A - Widows
Creek (1976)
Limestone
                                        Eastern
                                        coal
                                                   Full
                                                                                   (Unlined)
Ohio Edison -
Bruce
IL-r.sfield
C1975/J976)
Line
                     Eastern
                     coal
                                Full
                                                        C
                                                     (Fixed)
> ort.-.«=:m States
LiT.es tone
fly ash
                                                   Full
 (1976/1977)
                    Western
                    coal
                                              C
                                           (Clay
                                           lined)

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          Commonwealth Edison  (Will County)

          Commonwealth Edison has the most industrial experience
with disposal of stabilized sulfur oxide sludges.  The full-
scale limestone scrubber is installed on Will County's Unit 1
boiler  (163 Mw).  The disposal problem at this station is com-
pounded by the unavailability of sufficient acreage to contain
the sludge, the immediate proximity to the Illinois River, and
a high water table.  Commonwealth Edison has decided that the
sludge must be conditioned so that it will not leach to the
groundwater and that it must serve adequately as a landfill
material because the final disposal is planned on land which
is not owned by the power company.

          Commonwealth Edison has consulted with several com-
mercial sludge processors but, because of the economics involved,
they are attempting to develop their own fixation process with
the aid of the Chicago Fly Ash Company, under contract to carry
out the stabilization and disposal operations (Ref. 18).  Chicago
Fly Ash has employed the Civil Engineering Department of the
University of Illinois for assistance.  During periods of scrub-
ber operation, clarifier overflow is recycled to the scrubber
system via an interim pond and underflow sludge is pumped directly
into a ready-mix truck to which the fixation ingredients are added,
and mixed enroute to one of two cure ponds where the materials
are unloaded.   The present additives are reported to be approxi-
mately 10 percent lime and 20 percent fly ash on a dry basis.
The cure ponds are clay basins approximately 3 meters deep (10
feet) and total about 28,000 m2 (7 acres).   An arbitrary lining
thickness of about 0.3 m (1 foot) was chosen.   The clay has a
permeability coefficient of about 10~6 cm/sec, whereas the cured
material is expected to have a coefficient in the range of 10"7-
10"9 cm/sec.   The material cures for approximately 1 month and
is inspected by local authorities to obtain permission for
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 off-site disposal.   Criteria for  permission  is  unknown at  this
 time.   After permission,  material will  be  dredged from the basin
 and hauled to a nearby landfill area while the  other basin is
 being  filled.

           When the  scrubber  is not  in operation,  the disposal
 process continues,  dredging  up old  sludge  accumulated  during
 early  periods  of scrubber operation in  the 7 acre pond adjacent
 to  the clarifier.   The ponded sludge, settled to  50 percent
 solids,  is dredged  up  with a front  end  loader and taken to an
 open hopper equipped with a  drag  chain  feeder.  From the hopper
 the material is  conveyed  to  a point directly above a ready-mix
 truck  which receives the  sludge and the dry  additives  before
 proceeding to  the on-site disposal  basin.

           It is  not  yet known whether the  sludge  may pose  an
 environmental  hazard.  Liquors are  saturated in sulfate, and
 chloride  content is  about 800 ppm.   Corrosion assisted erosion
 was  experienced  at  this concentration but  use of  rubber-lined
 piping and pumps in  the recirculation system is reported to have
 eliminated the problem.   Tests are  being conducted to  improve
 the  final  product by the  elimination of cracks during  curing
 and  to verify  impermeability  in the  field.    It has not  yet been
 determined whether  the leachate contains trace heavy metals.
 It has been  reported that with enough lime,  a concrete-like
 product with 3000 psi  strength can be obtained.    For landfill
 disposal purposes, a product with a strength far  less  than  this
 is desired because of  the subsequent need  to dredge it  from the
 cure pond.  Data are not  currently available.

          The cost of  the current operation has  varied between
 approximately $5.25  and $10 00 per  ton of wet sludge (50 percent
 solids).  At the recent EPA enforcement hearings on power plant
pollution control, a utility spokesman cited an average cost of
                               -137-

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$17.10/dry ton, equivalent to about $8.55/wet ton  (50 percent
solids).  The higher end of the range probably reflects specific
case operations which include machinery breakdown and repair.
These costs are only operating and maintenance costs and do not
include pond costs and capitalization.  It appears that the pre-
sent philosophy is conservative in order to avoid possible pro-
blems due to variability in sludge chemistry.  The utility hopes
to optimize for steady-state operation taking into account scrub-
ber down-time.  A development program is planned with the aim of
reducing costs by increasing fly ash and reducing lime contents.
Additionally, a pug mill will be used to intermix additive in-
gredients with the sludge and the  ready-mix  truck  will be  replaced
by a dump truck.  It is believed that a vacuum filter must be
installed between the clarifier and pug mill to reduce the water
content of the sludge.  Unofficial estimates for disposal,  in-
cluding all costs, after optimization and achievement of steady-
state operation, are about $6.00-6.50/wet ton.  Adequate deter-
mination of the technical quality of the fixed materials and
attendant costs are not expected for at least a year.

          Duquesne Light (Phillips)

          Sludge samples from a small pilot lime scrubber system
at Duquesne Light's Phillips Station have been tested and
characterized by the Dravo Corporation.   For the full scale SO
                                                              X.
scrubbing system, which started up in the spring of 1974,  the
sludge disposal method entails a stabilized (fixed) landfill
operation in conjunction with clarification and curing ponds as
dewatering methods.  Sludge is removed as underflow from the
clarifier at 35-40 percent solids, treated with Calcilox (a
Dravo additive) and allowed to set for about 30 days in one of
three clay-lined curing basins.   A disposal development program
is being conducted at Phillips to evaluate the planned landfill
approach.  The cured sludge is dredged from the curing basin
                               138

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and hauled to the test site in an inactive ash disposal area
approximately 1 mile away.  The site includes two ponds lined
with Hypalon.  Each pond has underdrainage and overdrainage piping
to collect liquor for testing.

          At a recent symposium it was reported that the interim
ponds fill up more rapidly than anticipated, and as a result a
greater proportion of additive and fly ash is needed to give a
shorter curing time.  This resulted in a 10-14 day period for
curing instead of the planned 28-30 day period.  The consolidated
sludge is trucked to the test site and deposited in one of the
lined ponds.  However, 6 additional weeks of curing was found
to be necessary before the sludge could be leveled because of the
thixotropic nature of the material, thus slowing down the dis-
posal process considerably.  Consequently, not all sludge can
be put into the sludge ponds;  some is mixed and compacted with
dry fly ash on the normal ash disposal area.  Leachate monitor-
ing results will be presented in Section 2.0 (Ref. 19).

          Although not definitive, sludge disposal costs have
been estimated at approximately $3.00 per ton of coal burned;
the basis for this estimate is not known.  Utility spokesmen
recently reported that disposal costs actually incurred ranged
from $15 to $20 per ton on a dry basis, or $7 to $10 per ton of
wet sludge (Ref, 19).  Estimates are believed to include capital
costs,  common landfill site for fly ash and sludge, compaction,
covering with top soil,  and seeding.   Recently, at the EPA
enforcement hearings on power plant pollution control,  a Duquesne
spokesman cited $14-15/dry ton of sludge for disposal.   At 30
percent solids loading this is equivalent to about $4-5/wet ton
of sludge,  or $7.25/wet ton at 50 percent solids.

          Duquesne Light appears to have one of the more compre-
hensive research and development programs with respect to sludge
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disposal.  However, specific physical and chemical analyses to
be performed are not currently known and results are not expected
to be available for at least a year (Ref. 20).

          Kansas City Power and Light (Hawthorn)

          The full-scale boiler-injection limestone scrubbers
on Units 4 and 5 at Kansas City Power and Light's Hawthorn
Station operate under closed-loop.  Ponding is used both as a
dewatering technique and as final disposal.  An experimental
sludge pond has been constructed; 14 well points have been
placed outside the perimeter (Ref. 8).  A monitoring study is
being carried out in conjunction with Combustion Engineering
to determine possible adverse effects on the groundwater.  Samples
of groundwater were to be taken weekly for 2 months prior to
introduction of sludge to the pond,  and to continue for 1 year
thereafter.  Preliminary data are not 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.

          Northern States Power (Sherburne County)

          Northern States Power is currently employing ponding
operations to dispose of the sludge  and ash from the pilot-scale
limestone scrubber at Black Dog Station (Ref.  21).   Clarification
is used for primary sludge dewatering.  The pilot operation is
a research effort primarily to determine scrubber parameters
for the Sherburne County Station.   Sludge treatment and disposal
considerations are not known.

          At the Sherburne County Station, sludge generated by
two limestone scrubbers of the 1360  Mw total capacity, planned
                               140

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 for  start-up  in  1976 and  1977, will also be disposed of by
 ponding.  At  this  site clarifier underflow sludge will be sluiced
 to clay-lined basins and  excess water will be recycled to the
 scrubber  system  (Ref. 22, 23).  The scrubbing system will use
 two  stages--a variable throat venturi estimated to remove 55
 percent of the S02 and 90 percent of the particulates, and a
 marble bed scrubber estimated to remove an additional 15 percent
 of the SO2 and remaining  fly ash.  Because the coal ash contains
 about 17 percent CaO, fly ash removal and S02 control will be
 done simultaneously at a  low limestone stoichiometry (about 20
 percent).  The use of fly ash as a sorbent predicated the col-
 lection of particulates in the scrubbing unit.  However, it is
 believed that newer plants would use precipitators for fly ash
 removal for increased operating flexibility, reduced erosion,
 potential sales of dry ash, and allowance for single stage
 scrubbing.

          An  initial 10-year pond will be approximately 263,000
 m2 (65 acres) with 12 meter (40 foot) high dikes.   A second pond
will be added in the future, bringing the total capacity to
 about 468,000 m2 (165 acres) for an expected 35-40 year plant
 life.  Nearby clay will be used to line both ponds with an ap-
proximate 46 cm (18 inch)  thickness.   The disposal site is
 located on bluffs above the Mississippi River at an elevation
of 294 meters (965 feet).   Normal river elevation is 280 meters
 (920 feet).   Definitive disposal costs are not available.   How-
ever pond costs (including clay) are  believed to be in excess
of $30,000 per acre.   Although the utility's plans are not
clear,  the possibility exists that the Sherburne County Station
disposal method will undergo environmental monitoring by the
analysis of leachate from wells  placed around the  pond.
                               141

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          Louisville Gas and Electric  (Paddy's Run)

          The current and future sludge disposal practices for
 the Paddy's Run Station of Louisville Gas and Electric involve
 landfill operations.  The full scale scrubber, utilizing carbide
 sludge  Ca(OH)2 , is operated closed-loop and is installed on
 a 70 Mw unit fired with a 3.5-4 percent sulfur, 15 percent ash
 Kentucky coal.  All sludge is being collected independently of
 fly ash.  Precipitators exist on all stacks and are planned for
 future plants.  The sludge disposal process includes extracting
 underflow from the clarifier at "25 percent solids, vacuum fil-
 tration to 40-55 percent solids, and trucking in company-owned
 12 ton dump trucks about 1 mile to an off-site disposal area
 (borrow pit) excavated by the Kentucky Highway Department.  Fly
 ash is sometimes mixed in with the sludge by bulldozer at the
 disposal site.  The sludge is about 95 percent calcium sulfite
 and oxidation of the liquor is retarded such that the sulfate
 in the liquor is about 400 ppm.   Because of the poor settling
 characteristics of the sulfite,  flocculent is added to the
 clarifier and has reportedly been used successfully.   The sludge
 receives no stabilization treatment or other environmental
 control.  There are no apparent  plans for monitoring this dis-
 posal approach.   Costing for this disposal is not well defined;
 however, it is believed that the hauling cost is approximately
 $0.50/wet ton at this particular site.

          Future plans may include stabilization;  the utility
 is looking at processes commercially offered by Dravo and IUCS.
 Research in the area may be underway by the University of
 Kentucky and the state highway department (Ref.  24).   The use
 of fixed wastes in land salvage  of strip-mined areas  or as a
 support material for recovery of the 30-60 percent of the coal
 remaining in deep mines is being considered by the utility.
Alternative disposal schemes being considered include collection
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of clarifier underflow at 20-30 percent solids and addition of
dry-collected fly ash to increase solids content to 50-60 percent;
filtration to about 50 percent and possibly subsequent addition
of fly ash; and piping the solid waste slurry to the final dis-
posal site (Ref.  24).

          Southern California Edison (Mohave)

          At Southern California Edison's Mohave Plant, two
small pilot systems have been operated to evaluate both lime
and limestone scrubbing.   Both Dravo and IUCS have been involved
in treatment/disposal of lime and limestone sludges from these
pilot units,  respectively.   When the full scale units are opera-
ting, current plans are for each vendor to treat and dispose
of the sludge from a scrubber module (about 160 Mw equivalent).
Dravo will fix lime sludge and dispose of it by on-site landfill
estimated to have about 1 year storage capacity.  Liquor will
be recycled to the scrubber.  IU Conversion Systems (IUCS)  will
stabilize limestone sludge, convert it into aggregate and haul
it away.  In addition, dewatering techniques including centrifuga-
tion and vacuum filtration will be tested.  Cost data is unavail-
able.  Monitoring plans are not known.

          Ohio Edison (Bruce Mansfield)

          At Ohio Edison's Bruce Mansfield Plant, lime scrub-
bing will control the S02 from two 880 Mw units of generating
capacity.  The utility has contracted with the Dravo Corporation
for property purchase, site preparation,  and detailed design of
the sludge disposal process.  Current plans are to remove clarifier
bottoms sludge at about 30 percent solids and add boiler col-
lected fly ash,  lime grits from the pulverizer and slaker,  and
Calcilox additive to bring the total solids content to about 32
percent.   The composite slurry will then be pumped about
                              143

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10 km  (6.5 miles) to a large landfill site behind a 400 foot
high embankment.  Supernatant liquor will be recycled to the
scrubber system.  The disposal site is estimated to have a
30 year life.  Definitive disposal costs are not available al-
though Dravo estimates $2-4/ton of coal burned for a generalized
cost estimate, which includes capital investment ranging from
$30 to 60 million.  It is not known whether the utility plans to
evaluate the environmental adequacy of their disposal approach.

          TVA (Widows Creek)

          At TVA's 550 Mw Widows Creek limestone scrubbing
facility (to be started up in 1976) a new pond is under con-
struction which will have an initial 7-year capacity of 3.4
million m3 (120 million ft3).  This can be increased by 1.0
million m3 (35.3 million ft3) by raising the dikes.   An estimated
additional 2.7 million m3 (95 million ft3) of capacity,  for
which no provision has yet been made,  may be needed before 1995.
A total of 0.93 km2 (230 acres) of land is taken up by the new
pond which is sectioned for separate disposal of ash and sludge.
The pond is unlined, and the perimeter and divider dikes are
9.1 meters (10 yards) tall with 1.2 meters (3.9 feet) of free-
board and are constructed of compacted earth.   Under closed-
loop operation,  the scrubber wastes will be pumped to the sludge
disposal section of the pond as a 15-16 percent solids slurry.
The ash pond effluent will be released to the Guntersville
Reservoir.   A thickener will not be employed.   A final settled
density of 40 percent solids is expected, based on pilot plant
data showing 57-66 percent water content after 240 days  of
settling.   The overall disposal rate is calculated to be 115 m3/
hour (4050 ft3/hr) at full load.   Monitoring plans are unknown.
                              144

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          City of Key West  (Stock Island)

          Experience in untreated sludge disposal has been
obtained at the City of Key West's Stock Island facility where
a limestone scrubbing process has been installed on the 37 Mw
unit.  Residual oil is burned, thus resulting in a solid waste
of low ash content.  The scrubber solids are placed in one of
two settling ponds where drying takes place (Ref. 25).  Plans
are that while one pond is being filled, the other is emptied.
The filling time for each pond is 21 days.  Originally the dredged,
semidried sludge was to be dumped in an adjacent 81,000 m2 (20
acre) city-owned bay-bottom site of approximately 81,000 m2 (20
acres).  To date, neither pond has been dredged, but the material
will have to be disposed of in compliance with a Florida state
law which prohibits filling of submerged land productive to
marine life.   No firm decision has been made regarding a long-
term approach for sludge disposal.

          Arizona Public Service (Cholla)

          Because of the climatic conditions at Arizona Public
Service's Cholla facility,  a solar evaporation pond is being
used as a sludge disposal technique.   The 115 Mw limestone
scrubber system generates sludge at the rate of 3.1 metric tons
per hour on a dry basis.   The system is operated closed-loop
relative to the sludge recirculation tank out open-loop with
respect to the pond.   A bleed stream from the scrubber recir-
culation tanks is sent to two sludge storage tanks which are
emptied about once per shift to the existing ash pond where
solar evaporation and settling are responsible for dewatering
(Ref.  16).
                              145

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          Mitsui Aluminum Company

          For purposes of comparison, the Mitsui Aluminum
Company's installation is discussed here.  Two dual-stage
venturi scrubbing systems utilizing carbide sludge as an absor-
bent have been retrofitted to the 156 Mw power plant.  Closed-
loop, continuous operation has been demonstrated since March
1972, with no scaling or plugging problems.  A bleed stream
from the system containing mostly calcium sulfite (80 percent)
and calcium sulfate is disposed of in a preexisting 90,000 m2
(22 acre) ash pond (Ref.  26).  This pond was constructed by
excavating a filled area next to the sea, forming a dike 16
feet high.  Since the outer wall of this dike is ~50 feet from
the sea, the inner wall was lined with a vinyl film to prevent
leaching through the wall (Ref.  27).   The water table (sea
level) is anywhere from 1 to 23 feet below the pond bottom
depending on the tide.  Pond liquor which is saturated with
respect to calcium sulfate is recycled via rubber-lined piping
to the scrubber for reuse.   The ponded sludge, which in some
cases will support the weight of a man,  remains a very thixotropic
material about 6 inches below the surface.   Now that successful
performance of the S02 control system has been achieved,  pro-
duction of high quality gypsum by incorporating a proprietary
oxidizer is being considered.  There is  currently a definite
market for by-product gypsum in Japan.

          In summary, it  appears that firm decisions for the
total disposal problem have not  been made by some utilities.
Those that have selected  an approach either will not commit
sludge to the disposal site for a period of time during which
changes can be made,  if necessary,  or are uncertain of the
approach they have chosen.   Neither the  utilities nor the sludge
conditioning processors are expected to  readily identify all
environmental problems, solutions,  or economics associated with
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 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 effectiveness 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 has historically been
 a favored technique in a number of industries; e.g., gypsum
 sludge from fertilizer plants, phosphate slime from phosphate
 mining, and fly ash from coal burning facilities.  The mechanics
 of pond construction and pond 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 representative 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 asso-
 ciated with soluble species in the sludge liquor and solid
 phases, and (2)  the land deterioration associated with nonsettling
 sludges.   In the past,  there was often little attention paid to
 pond site selection or to pond lining.   The general attitude
 seemed to be that fine particles from the pond liquor would
 eventually plug the soil and minimize percolation.  However,
 careful study of pond sites is now required and, when there is
 a danger of groundwater pollution,  suitable pond linings must
be provided.   Changes in regard to pond overflow may be especially
 significant.   In the past,  dilution by the receiving stream was
 considered to provide acceptable treatment.  Regulations are
moving toward a "no degradation" basis which means pond overflow
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 must  be  eliminated in  almost  all  cases.   This will  require
 total recycle  of  pond  liquor.

           One  advantage  of ponds  is  that  the volume can be
 increased  as needed by building up the sides of the pond.   In
 some  cases  (e.g.,  gypsum sludges  from the fertilizer industry)
 the pond walls  can be  built up using settled solids from within
 the pond.   In  the case of scrubber sludges this may require
 special  treatment (stabilization  by addition of chemicals which
 undergo  pozzolanic reactions with the sludge).  Ponded scrubber
 wastes are  typically not  stabilized; however, stabilization of
 that  sludge used  for building up  the walls via certain com-
 mercial  processes  (discussed in Subsection II-D 1.2) might
 provide  a suitable  approach.

 1.0       Survey  of Technical Features of Ponding

          In addition  to  consideration of factors such as geology,
 topography, and hydrology necessary for site selection, the basic
 technical features  involved in the design and operation of all
 ponds include the  following:

          1.  Sluicing of material to pond.

          2.  Settling.

          3.  Pond  lining.

          4.  Pond management.

The general characteristics of each of these technical areas
are described below with special emphasis placed on those aspects
specifically dealing with scrubber sludge.
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          1.1  Sluicing Operations

          Transport of waste scrubber sludge to the ponding
site is carried out in most cases by sluicing operations; i.e.,
piping the slurried solids.  Individual sludge properties such
as viscosity, velocity, temperature, composition, particle size,
and solids concentration affect the pumping characteristics of
the material.  Also of major concern is the distance to be
covered.  Special problems specifically related to sulfur oxide
sludges such as corrosion or erosion potential also require
investigation.

          In general, the transport of solids in pipes depends
on the use of a carrier fluid to transmit pressure from the
pump or compressor to the solid being moved.  The viscosity of
the material greatly influences the transport characteristics,
since it is a measure of a resistance to flow.  The viscosity
of a number of individual scrubber sludges has been determined;
the data were presented in Section I-E of this report.  Specific
characteristics such as thixotropic or rheopectic behavior
unique to some scrubber sludges are related to viscosity and,
therefore, will influence sluicing operation parameters.  For
instance, sludges with high sulfite composition exhibit thixo-
tropic behavior.   This observed loss of viscosity with stirring
would result in lower head loss at constant velocity of the
fluid.   A different sludge, however, has been shown to exhibit
rheopectic behavior.  This would tend to have an adverse effect
on pumping operations.

          In addition,  the critical velocity for a particular
sludge must be determined, since it is the flow velocity at
which solids are most economically moved for a given pipe size.
This velocity will occur somewhere in the turbulent flow region;
i.e.,  the region in which particles may move in any direction
with respect to each other.
                              149

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          Other technical aspects of pipelining of sludge
requiring consideration prior to design of a system are materials
of construction and possible use of pumping aids.  In addition,
transport can be accompanied by erosion problems due to the
physical nature of the solids.  In many installed lime/limestone
systems, much of the piping, blades, and pumping equipment used
to transport slurries are rubber-lined to protect against the
abrasive properties of the slurry, especially in pipes carrying
sludges of higher solids content.

          The use of long distance piping systems is increasing
rapidly since the demonstration of technical and economic
feasibility.  Table II-4 summarizes commercial applications
which have been installed in recent years.

          The economics of solids handling by sluicing or
piping operations depends mainly on two factors:  amount to be
handled and distance to be covered.  Thompson et al.  reported
total pipeline transport costs (including power, labor, supplies,
and capital charges) to range from $1.76 per dry metric ton of
sewage sludges (3.5 percent solids) for a 40 kilometer, 900
ton/day system to a maximum cost of $22 per dry metric ton for
a 160 kilometer,  91 metric ton/day system (Ref.  28).

          The results of a 1970 nationwide survey of 22 utilities
show  that it was costing $0.033 to $1.21 per metric ton (average
of 25 plants, $0.50/metric ton) to sluice ash to the on-site
disposal area (Ref.  8).   Another survey in which off-site waste
disposal costs were reported gave figures in the range of $0.01
to $0.10 per cubic meter per kilometer ($.05-0.50/1000 gal.-mile)
for pipeline conveyance of brines and sludges (Ref.  29).   These
costs did not include fees charged by the receiving agency.
The author of the report concluded that pipeline conveyance
                             150

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                                  Table I1-4.   SUMMARY OF COMMERCIAL SLURRY PIPELINES3
Pipeline
Consolidation Coal
American Gilsonite
Rugby Cement
Columbia Cement
South African Companies
Savage River Mines

Black Mesa Pipeline, Inc.

Hyperion Wastewater
Treatment Plant
Mogden Wastewater
Treatment Plant
Easterly Pollution
Control Center
Location
Ohio
Utah
England
Columbia
South Africa
Tasmania

Arizona

Los Angeles

England

Cleveland,
Ohio
Material
Coal
Gilsonite
Limestone
Limestone
Gold tailings
Iron
concentrate
Coal

Digested sewage
sludge & effluent
Digested
sewage sludge
Raw sludge

Length
(miles)
108
72
57
9.2
21.5
54

273

7.5

7

13

Diameter
(inches)
10
6
10
5
6 & 9
9

18

22

12

12

Throughput
(million tons
per year)
1.30
0.38
0.70
0.35
1.05
2.25

5.70

_

—

.

Solids
(specific
gravity)
1.40
1.05
2.70
2.70
2.70
4.90

1.40

1.80

1.80

1.80

Weight
(percent
solids)
52
46
61
55
50
60

50

1.0

4.0

2.5

Years in
Operation
or Status0
6C
11
5
25
14
2

In startup
phase
11

33

32

      28.
bAs  of 1971.
^Commercial  operation ceased  in  1963  for non-technical  reasons.  Now maintained  in  standby condition.

-------
 is  the most  economical mode  for  quantities  in excess of  100
 cubic meters  (26,000 gallons) per  day  irrespective of  distance.

          Lord of Dravo Corporation cited a cost for slurry
 pipeline transportation of SOg  scrubber sludge,  exclusive of
 capital  investment costs of  $0.02/ton mile of wet sludge  handled
 (Ref. 30).

          1.2  Settling

          Physical properties and  settling characteristics of
 scrubber sludges have been discussed in Section I-E.

          1.3  Pond Lining

          Pond linings have been finding greater favor in recent
years.   In some cases the intent has been to decrease pollution;
in other cases the intent has been to avoid loss of water which
could be recycled.  In many areas, clay, concrete,  wood,  or
metal has been used as a liner.   Recently,  synthetic linings
are finding increasing usage.  These include the following
materials which are offered in different formulations  (Ref. 31).

          Polyvinyl Chloride

          A rough, highly puncture-resistant material.
          It resists  flame, many chemicals,  oils, greases,
          ozone,  solvents,  abrasives and microbiological
          activity.   It has good weatherability and high
          strength-to-weight ratio.  However,  exposure
          to heat causes  various degrees of chemical
          degradation;  it  is susceptible to staining by
          sulfides;  adhesion to  metal or wood is poor;
          low temperature  increases stiffness.
                             152

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Natural Rubber

One of the oldest sheet-lining materials.   It
has high tensile strength and good chemical
resistance but somewhat poor resistance to
sunlight.

Synthetic Rubbers

Butyl and EPDM rubbers are highly impermeable
to water,  very flexible, and durable.  They
resist wear, tear, ozone, and aging and have a
wide range of operating temperatures and
excellent weatherability.  They have low
resistance to petroleum solvents and aromatic
and halogenated  solvents.  These rubbers are
denser than natural rubber and neoprene and
are suitable for higher temperature conditions.

Hypalon rubber is a chlorosulfonated derivative
of polyethylene  and was developed to withstand
the combined effects  of weather, oil,  and
several chemicals.  It resists puncturing,
abrasion,  tearing, ozone, aging  (ultraviolet),
and has very good weatherability.   It  has
comparatively  low tensile strength.

Neoprene  rubber  is quite  similar to natural
rubber but has better resistance to certain
combinations  of  oils  and  acids.
                     153

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          Polyethylene

          This plastic is tough, highly flexible, inert
          to solvents, and resistant to low temperatures.
          It has poor weatherability and puncture-
          resistance.  It has high elongation but may
          become thin in localized areas under tensile
          stress.  Polyethylene is available in three
          types—low, medium, and high density and as
          chlorinated polyethylene.

          Polypropylene

          This material offers a balance of properties
          rather than any one outstanding characteristic.
          It has good chemical and heat resistance,
          high tensile strength, high flexibility, and
          low permeability to water.  It has poor
          weatherability and poor resistance to oxidizing
          solvents.
          Nylons have good heat resistance,  a wide range
          of operating temperatures,  low permeability to
          water, high tensile strength, and good flexibility.
          Their moisture absorption is high and weather-
          ability poor.   They resist  most oils and chem-
          icals except acids.

          1.3.1  Lining Selection - In selecting a liner,  many
specific criteria must be designated, including the following
(Ref.  31):
                              154

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          1.  The liner should have high tensile
              strength and flexibility and should
              be able to elongate sufficiently
              without failure.  It should resist
              abrasion, puncture, and the fluid
              to be stored, and should conform to
              other desired physical properties.

          2.  It should have good weatherability
              and a guaranteed long life.

          3.  It should be immune to bacterial
              and fungus attack.

          4.  It should be able to stand the desired
              temperature variations and other
              ambient conditions.

          5.  It should be capable of being repaired
              easily at any time during its life.

          1.3.2  Leak Detection for Lined Pond - Sometimes a
leak detection system must be built into the pond system,
especially when toxic or polluting chemicals are to be stored.
Two types of leak detection systems are (Ref. 31):

          1.  Underbed Drainage System.   This consists
              of a network of gravel-packed drainage
              canals or perforated drainage pipes.
              All seepage is channeled to the outer
              perimeter of 'the pond and collected in
                              155

-------
              a sump outside the pond where inspections
              can be made.  A variation is to monitor
              the fluid in standpipes (piezometers)
              placed within the pond.  The tops of the
              pipes extend above surface level; the
              bottoms penetrate the liner into the
              underlying soil.  Wells in the proximity
              of the ponds may also be utilized, al-
              though considerable leakage may have
              occurred before well water analysis in-
              dicates the problem.

          2.  Ground-Resistivity Measurement System.
              Several metallic pins may be buried beneath
              the pond.  Using a resistivity meter,
              ground resistivity between these pins may
              be measured.  A marked decrease in ground
              resistivity may indicate pond leakage.

          1.3.3  Lining Costs - Some approximate cost figures
have been estimated for lined ponds.  Factors influencing the
price include size and type of lining required.  A 1974 cost
estimate for a 46 cm (18 inch) thick clay liner installed in
several large ponds in the Midwest was $10.80/m2 ($9.00/yd2).
The clay was transported by truck about 48 km (30 miles) from
the clay pits to the pond site.  If suitable clay had been
available on-site, the lining could have been constructed for
$1.80/m2 ($1.50/yd2) (Ref. 32).  The cost of clay lining for
a 0.02 to 0.04 square kilometer pond (enough storage for about
10 Mw equivalent) would then amount to $36,000 to $72,000
utilizing clay on-site.
                              156

-------
           Other sources of installed liner costs provided the
 preliminary data presented in Tables II-5 and II-6.   It should
 be noted that these cost data employed 1973 dollars  and may not
 represent current costs; however,  relative cost comparisons
 should be valid.

           Figure II-l presents typical lining cost data for
 installed liners at the field site.   The  wide range  of  costs
 for each type of lining results from varying labor costs,  varying
 transportation costs,  and price discounts for large  purchases
 (Ref.  32).

           Figure  II-2  shows  the 30 year average disposal cost
 as  a function of  the  depth of raw sludge  in the pond.   Two
 liner  materials were  considered for  comparison:   0.508  mm (20
 mil)  thick polyvinyl  chloride (PVC)  at an installed  cost of
 $2.33  per  square  yard  including a soil cover of 15 cm (6 inches)
 and  0.762  mm  (30  mil)  thick  Hypalon  at a  cost  of  $3.85  per
 square yard installed.   The  pond configuration  used  had a  0.9
 meter  (3  foot) freeboard.  It was assumed that  the land need
 for  30 year disposal operations  would be  purchased initially,
 but  the ponds would be constructed each 10 years  as  the previous
 one became full.  The  land costs used were  $404 and  $2020  per
 hectare  ($1000 and $5000 per  acre).  Figure  II-2  illustrates
 the effect of land cost  on ponding costs  and also indicates
 that there is an  optimum sludge  depth which would result in  a
minimum disposal  cost.

          Very recent data (January  1975)  indicate an installed
cost for 30 mil unsupported Hypalon in a  1-10 acre pond of $6.00
to 7.20/m2 ($5.00 to 6.00/yd ).  The cost savings realization
for a larger pond is indicated by the fact that the same lining
for a 100 acre pond would cost about $4.80/m2 ($4.00/yd2).  The
                               157

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                Table II-5   PRELIMINARY ESTIMATE OF COSTS  OF  POTENTIAL LINERS  FOR  SANITARY  LANDFILLS
                                   POLYMERIC MEMBRANES  -  PLASTICS AND RUBBERS
                                                                            a,b
Type
Butyl rubber, unreinforced
Chlorinated polyethylene
(CPE) , unreinforced
Chlorosulfonated polyethylene
(Hypalon) w/nylon scrim
i-1 Ethylene propylene rubber
TO (EPDM), unreinforced
i
Neoprene, unreinforced
Polyethylene film
Polyvinyl chloride,
unreinforced

Thickness ,
mils (in.)
31.3 (1/32)
46.9 (3/64)
62.5 (1/16)
20
30
20
30
45
31.3 (1/32)
46.9 (3/64)
62.5 (1/16)
31.3 (1/32)
46.9 (3/64)
62.5 (1/16)
10
20
10
20
30
Cost, $ per
Price of Fabric
Roll Goods Cos
$2.25
2.70
3.33
1.58
2.25
square yard
Field
ation Installation
tsc Cost
$1.
1.
0.
1.
1.39 0.
1.66 i.
2.61 0.45
2.88
2.00
2.42
3.20
2.07
2.97
0.36
0.72
0.52
0.90
1.33
1.
1.
2.
2.
0.
0.
0.
08-
71
99-
26
72-
08
17-
71
24-
43
63
54-
99

Installed
Costd
$3.33-
5.04
2.57-
3.51
2.56-
4.41
3.17-
4.91
4.31-
5.40
0.99-
1.35
1.06
2.32
 Ref. 33
 Represent 1973 dollars
 Cost of fabricating rolled sheeting into panels.
 Soil cover not included;  all  of  these polymeric membranes require some soil cover, cost of which can range from
$0.10  to 0.50 per  square yard  per foot of  depth.

-------
     Table II-6.  PRELIMINARY ESTIMATE OF COSTS OF POTENTIAL LINERS
         FOR SANITARY LANDFILL SOILS, ADMIXTURE MATERIALS, AND
                           ASPHALT MEMBRANES3
Type
Soil
9
18
of Liner
+ Bentonite
Ibs/sq yd
Ibs/sq yd




Cost
Materials
(Volclay)c
(1 psf)
(2 psf)
0.
0.
06
12

77-
Per
Square
Installation
0
1
.66
.05

Yard

Instil IPHD
0.
1.
72
17
 Soil  Cement
    6  in.  thick + sealer  (2  coats,
       each 0.25 gal./sq  yd)                                     1<25
 Soil  Asphalt
    6  in.  thick + sealer  (2  coats,
       each 0.25 gal./sq  yd)                                     L 25
 Asphalt Concrete  - Dense-graded paving
    with sealer coat
    Hot mix - 2  in. thick                                    i 9n   , 7n
    Hot mix - 4  in. thick                                    ^35 - 3.25
 Asphalt Concrete  - Hydraulic
    Hot mix - 2  in. thick                                    , cn   9 ,c
    Hot mix - 4  in. thick                                    J;gj ~_ £Jg
 Bituminous Seal  (catalytically blown
   asphalt)
   1 gal /Sq  ^                     0.27                    1.50 -  2.00
                                                            (with earth
                                                            cover)
Fabric sealed with asphalt emulsiond
   (Polypropylene mat sprayed with
   asphalt emulsion)                 0.70-0.77    0.56 -      1 26 -  1 87
                                                 1.10
   aRef.  34
   c
    landfiliesite  dep6ndS  °n  type  °f  Soil  available  at  or  near  the

                                    159
Depends on size of job.

-------
          H-
          00
          c
          I-J
          to
                                             INSTALLED  COST,  $/ Sq yd
                                   POLYETHYLENE -  10 mils
                                                  POLYVINU CHLORIDE  -  10 mils
o
I
          3
          CO
          rt
          U)
(D



r1
H-
3

i-i

n
o
01

CO
          8?
          l-h
      CA
      CO
                          z
                          o
                          H
                          n
                          en
            3  H-
              I-1


            II   II


            NJ O
            •  •

            Oi O
            •P- N3


            O  ^>

            3  _
                                                       POLVVINYL CHLORIDE  -   20  mils
                                           PETROIAT FABRIC -  125 mils
I BUTYL ROBBER - 30 mils



     .CiLORINATED

      POLYETHTLEHE  -  30  mils


      HYPALON - 30 mils



            EPOI ROBBER  -
            30  mils
                                                                                         —  18 inches
                                                                             BITOIIHOOS  CONCRETE

-------
l-
co
o

0  3
w
o
O.
(O
(O
                TOTAL  COST INCLUDING  LAND

                       ($5000/Acre)
      TOTAL  COST

      INCLUDING  LAND

      ($1000 PER Acre)
                              TOTAL  COST

                              WITHOUT  LAND
               INSTALLED  LINER  ONLY
                       PVC  - 20  MIL

                         I         I
              10        20        30

                    SLUDGE DEPTH,  Feet
40
      CO
      O
      O
      CO
      o
      a.
      CO
      5 2

      til
      o
      a
                                                  CO
                          ^-TOTAL COST INCLUDING  LAND

                           X       ($50OO/Acre)
                                TOTAL COST

                                INCLUDING

                                LAND

                               ($10007 Acre)
                                       TOTAL  COST  WITHOUT LAND
INSTALLED  LINER  COST
                           HYPALON  -  30  MIL
    iO        20        3O

           SLUDGE DEPTH. Feet
                                                  40
              Figure  II-2.   Disposal Costs - Ponding Sludge,  50 Percent Solids

                                     (30 year average)  (Ref.  32).

-------
cost for 30 mil fabric-reinforced Hypalon for the smaller
pond of 0.40 to 4.0 hectares (1-10 acres) would be $6.80 to
7.90/m2 ($5.70 to 6.60/yd2); for a 40 hectare (100 acre) pond
the cost would be about $5.74/m2 ($4.80/yd2) (Ref. 35).

          These cost figures when compared to those in Figure
II-l indicate the recent cost escalation of materials, emphasizing
the fact that the data are useful for relative comparisons, but
may not be valid for design purposes.

          Generally, the costs presented to not include the
costs for site and surface preparation nor the cost of ground
cover, which would be required in almost all cases.  The surfaces
on which the liners are to be placed must be graded and smoothed
for drainage and compacted to prevent settling of the ground
below the liner materials: i.e., soil asphalt, soil concrete,
and the asphalt concretes.  The cost of site preparation is
essentially the same for all the liner systems, though it is
possible that some of the liner systems may not require as much
effort in surface preparation as others.  An earth cover,
preferably one which is somewhat porous, would appear to be
needed as a part of the liner system.  Such soil covers will
thus allow the large landfill equipment  (e.g., caterpillar  tractors
and compactors) to operate on the liners.

          With the exception of liner applications noted in
Section II-B, there are no known applications of liners for ash
or sludge disposal.  Consequently, performance data on liner
materials for sludge disposal applications is not available.
However, Voyer and Cluff  (Ref. 36) noted that the seepage rate
of Wyoming Bentonite clay exposed to high concentrations of
calcium and magnesium salts increased to 0.1 to 0.4 inches/day
after the first year and  to 5.5 to 9.0 inches/day after 4 years.
                               162

-------
More  data  is  required, but  this 25- to 50-fold increase suggests
that  permeability of  clay may increase significantly with time.

           Additionally, the environmental requirements of liner
materials  and consequently  their cost-effectiveness is not well
defined.   As  a point  of reference, $1.0/yd2 is equivalent to
about $5/Kw capital cost and 0.15 mills/Kwh annual cost for a
ponded sludge (with ash) from a 1000 Mw coal-fired unit (Table
1-8,  Column 5) based  on 15 years storage life, 10 feet deep.

           1.4 Pond Management

           The start-up and day-to-day operation of a disposal
pond  involves answers to the following questions pointed out by
Slack and  Potts (Ref. 7).

           1.   Will the pond be operated as a single
              unit or divided into sections?

           2.   Will the original depth be the limit
              or can walls be built up using the
              settled material?

           3.   Will the pond be partially filled with
              water before operation begins?

           4.   Can the pond be filled to the top of
              the dike or must some freeboard be
              allowed?

          The first question is related to the settling char-
acteristics of the material as previously discussed (Section I-
E).   Ash ponds are typically operated such that the slurry
                             163

-------
 enters  one  end  of the  single pond.  As  it  flows  to  the  opposite
 side, the well-settling  ash drops out and  a pool of supernatant
 forms at the  far  end.  The effluent is  removed via  weirs or
 standpipes, thus  allowing continuous operation of the pond until
 full.   In contrast, waste gypsum from phosphoric acid manufacture
 is  usually  ponded in several units.  Since the settling char-
 acteristics of  the waste are poor, one  pond is allowed  to dry
 and be  emptied  while another pond is being filled.   This may
 also be necessary in ponding of sulfur  sludge.

          The second question deals with the dimensional
 stability of  the  settled material.  In  ash pond management, the
 settled ash is  seldom used to extend the height  of  the walls
 because its spherical form results in a low angle of repose.
 Waste gypsum, on  the other hand, lends  itself readily to this
 application.  Excavating equipment is employed to pile up the
 dried material  as high as 30 meters.   Preliminary data for un-
 treated scrubber  sludges presented in Section I-E are not yet
 sufficient to predict whether this type of operation could be
 successfully applied.

          If the  scrubber is operated in a closed-loop mode,
 smooth  start-up may necessitate partial filling of the disposal
 pond beforehand   This would provide a source of recycle water
 at  the  onset of operation and eliminate the need for additional
 start-up pumping arrangements.   This  would produce overall
 increasing concentrations with respect to composition of liquor
 associated with solids until steady-state is achieved.

          The amount of freeboard required for any particular
pond is  chiefly a function of climate.   If the area receives
 large amounts  of precipitation during periods  when evaporation
rate is  low, then more freeboard would be necessary than for
                               164

-------
ponding operations in hot dry climates.  Ponds which lack drain-
age provisions would also tend to require greater freeboard.

2.0       Potential Water Pollution Aspects of Ponding

          Potential problems associated with contamination of
surface and/or groundwaters by untreated sulfur oxide sludges
exist in the following areas:

          1.  Soluble trace elements.

          2.  Chemical oxygen demand due to sulfite
              oxidation to sulfate.

          3.  Excessive total dissolved solids.

          4.  Excessive levels of specific species;
              e.g., sulfate, chloride, carbonate,
              calcium, and magnesium.

          5.  Excessive suspended solids.

These could present problems via leachate and/or run-off routes.

          The composition of the leachate formed is  a function
of several factors including composition of coal, limestone,
and make-up water; chemical composition of the sludge solid
phase;  pH;  and solubility of the individual species  present.
The nature of the leachate from untreated sludge can be judged
by examination of liquors associated with scrubber samples,
especially clarifier supernatant or scrubber recycle liquor in
closed-loop operation.   Data indicate that many of the potentially
leachable elements originate with the coal.  For this reason,
                              165

-------
examination of liquors associated with ash ponds also provides
some insight into potential leachate compositions.  Available
chemical analyses for untreated sludges and ash have been
presented earlier in Section I-E of this report.  The potential
problems associated with a ponding operation are discussed below.
Although leachate and run-off are similar in nature, they are
considered separately in this report.

          2.1  Leachate From Sludge Disposal Ponds

          An unlined disposal pond provides a potential for con-
tamination of groundwater.  Unlike a landfill, the sludge is
always saturated with water, and the "head" of liquor in the
pond assures a continuous driving force for percolation.  Under-
lying strata may also become saturated; and if an unconfined
aquifer exists beneath the pond, the pond site may act as a
"recharge" zone for that aquifer.  If no unconfined aquifer
exists, the pond liquor may continue to seep into the existing
strata beneath the pond.  It is not clear whether this would be
construed as a detrimental environmental impact.

          Given that an aquifer does exist, the important
factors are the rate at which pond liquor permeates into the
groundwater and the chemical composition of that liquor as it
enters the aquifer (any suspended material will probably be
filtered out by the soil).

          It should be noted that movement of groundwater can
be very slow; e.g., about 1 meter per year laterally.  It also
is important to note that groundwater movement may occur in a
"plug flow" fashion.  Given that a pollution source exists
above an aquifer, under some circumstances vertical flow of
polluted water into the aquifer may be greater than the natural
                              166

-------
 lateral movement  of  the  groundwater.  This, plus  the  "plug
 flow"  nature  of groundwater, means  that  there may be  little
 opportunity for dilution of  the polluted water even over  a
 period of years.   This situation  is very different from the
 case of allowing  pond overflow to enter  a  stream, where even
 high pond liquor  concentrations may be diluted in a matter of
 minutes.

           With regard to groundwater  contamination by constituents
 of pond liquor, there are some possible  mechanisms to reduce the
 impact of the pond liquor.   These involve  a group of  reactions
 commonly  referred to as  "soil attenuation" mechanisms.  Reactions
 between solution  species and soil particles can occur via adsorp-
 tion,  ion exchange,  or precipitation.  Since ion  exchange and
 precipitation are essentially displacement of one ion by  another,
 only simple adsorption provides a true removal mechanism.  For
 ion exchange  and  precipitation, it  is to be hoped that a  toxic
 species might be  lost from solution and  a  less toxic  species
 gained; however,  there is no assurance of  this.   It is unlikely
 that a large  change  in total dissolved solids would occur via
 soil attenuation  mechanisms.  Some  dissolved species  such as
 heavy  cations might, however, move  through the soil slower than
 the liquid in which  they entered.  Other species, generally
 anions such as N03~, P0,,~3 and especially  Cl", which  may  not
 enter  into adsorption or exchange reactions, would move through
'the soil  faster  than the liquid in  which they entered.  The
 law of electroneutrality requires that any leachate  (ionic
 solution) must contain an equivalent  quantity of  cations  and
 anions.   Unfortunately,  no data are yet  available on  this
 important topic  for  scrubber sludge liquors although  the  soil
 type  is clearly  important.   STEAG,  a  government organization
 in Germany, has  instrumented a disposal  pond for  lime scrubber
 sludge to determine  effects  on groundwater.  This group has been
                               167

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 visited and a  description of their system is presented in
 Reference  37.   So far their monitoring system has not detected
 any  contamination of the aquifer which is located only about a
 meter below their unlined pond.  However, their observation wells
 are  far enough away from the pond that sufficient time probably
 has  not elapsed for any contamination to reach the wells.

           Combustion Engineering and Kansas City Power and
 Light are  also doing a study of this type, but no results have
 been released.  A large study of soil attenuation mechanisms
 is being done  for municipal wastes under the sponsorship of
 EPA1s Solid and Hazardous Waste Research Laboratory (SHWRL).
 Their experimental program is just getting underway, however,
 and  no results  are yet available.  There is one piece of
 information which, although not well documented, seems to be of
 significance in regard to pollution of groundwater by leachate.
 That is that no pollution problems have been documented due to
 ash  pond leachate, even though ash ponds without liners have
 been widely used in all types of soils for decades.   Even
 though no problems have been attributed to ash ponds,  the infor-
mation on the  chemical properties of sludge indicates  a need for
 proper site selection and possibly lining of ponds.   In some
 situations a continuing monitoring program may be necessary;
 for  example,  when a disposal pond is to be located over an un-
 confined aquifer.

          2.2  Overflow of Pond Liquor

          Disposal ponds have typically been operated  with less
than total recycle of pond liquor.   The excess liquid  has often
been permitted to flow into receiving streams with little
treatment beyond neutralization,  settling,  or skimming.   In
addition,  spills have occurred frequently.
                              168

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          Newer and more stringent regulations on waste water
 disposal will likely reduce the practice of overflowing excess
 liquor into lakes and streams.  This will necessitate the use
 of  closed-loop (total recycle) operation for scrubber sludge
 disposal by ponding, with treatment of any blowdown (purge)
 streams.  Alternatively, blowdown streams might be disposed of
 via evaporation,  deep well injection, or disposal in the ocean.
 This sort of operation, combined with proper site selection,
 design, and lining of ponds, should eliminate contamination of
 surface or groundwater by ponded scrubber sludge, thus minimizing
 any water pollution problems associated with sludge ponding.
 A potential problem would be the eventual land reclamation of
 the pond site due to the resistance to dewatering exhibited by
 many unstabilized sludges.   This problem might be particularly
 troublesome in those areas with high annual rainfall and low
 annual evaporation;  this is discussed further in Section II-D.
 Sludge dewatering techniques are currently under investigation
 in  an effort to make sludge a suitable disuosal materials.

 D.        DISPOSAL BY LANDFILL

          A second approach to the problem of disposal of waste
 solids generated by lime or limestone scrubbing systems is
 landfill.   Currently less than 40 percent of existing or plan-
ned installations have adopted this alternative, while approxi-
mately 60 percent have included ponding facilities.

          Characterization of lime/limestone scrubber sludge
 thus far has revealed a nature not readily suitable to untreated
 landfill disposal.   The sludge does not settle or dewater readily,
and the preliminary results of one experiment have indicated
that once dried,  the untreated material will reabsorb moisture
to its original water content (see Section I-E).  A second
aspect of untreated sludge  is its leachate characteristics,
                               169

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also discussed in Section I-E.  For these reasons, chemical and
physical stabilization processes are being marketed and are now
being demonstrated.  The marketing agents for these fixation
techniques claim that conversion to a physically and chemically
stable landfill material is possible.  In some cases, a salable
by-product is reportedly made.

          In the following discussion, the term landfill will
mean the disposal of a scrubber sludge treated via dewatering
and/or stabilization techniques.

1.0       Survey of Technical Features of Landfill Disposal

          The technology associated with disposal of waste
scrubber sludges by landfill operations is currently in the
development stage.  There are three basic features requiring
discussion to accurately describe the current state of tech-
nology regarding this disposal method:  dewatering, stabiliza-
tion, and handling of sludge.

          1.1  Dewatering Techniques

          The object of any sludge dewatering process is to
recover the solid content of the sludge in a concentrated form
suitable for disposal or further processing.  The liquid content
is recovered from suspended solids for recirculation within the
process or for safe discharge as a processed effluent.   Presented
in this section of the report is a discussion of methods avail-
able for dewatering of air pollution control system sludges.
Many of these techniques have been experimentally and indus-
trially applied to sludges generated by lime or limestone wet
scrubbing systems.  Table II-7 is a summary of the results of
some of these recent studies.
                               170

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                                                    Table II-7.   SUMMARY OF SLUDGE DEWATERING TECHNIQUES
  Method
                      Application
                                                     Sludge
                                                            Results
                                                                                                                Comments
                                                                                                                                     Reference
Clarification
                    Currently used as primary
                    dewatering device on
                    full-scale systems
                            Various lime and
                            limestone scrubbing
                            system sludges
Limestone sludges thicken
"better" than lime because
of coarse unreacted additive
present
                              Ref.
                    Bench-scale
                                                Shawnee  limestone
                                                system sludge
                                                        20%  solids achieved
                                                                                                                   Ref. 38
Bed Drying
Bench-scale column
                            Limestone system
                            sludge
                                                                          Steady state drainage rate  was
                                                                          0.046 cm /min.  Sludge with
                                                                          "relatively" high sulfate con-
                                                                          tent settled to 67% solids  with
                                                                          or without  underdrainage. High
                                                                          sulfite sludges settled  only
                                                                          to 52% solids with underdrainage
                                Air-dried sludge exposed to Ref. 38
                                water regained original
                                moisture  (51.7%)
Centrifugation
Bench-scale tests
                            Various lime-scrubbing
                            system sludges
47-57% finals solids content
(original:  19-44%)
                                                                                                          Fly ash was present in the  Ref. 14
                                                                                                          samples
                   Bench-scale tests
                   (short-term)
                            Limestone scrubbing
                            system sludge
53-64% solids achieved
(feed was 10-29% solids)
                              Ref.  7
                              Ref.  39
                   Full-scale
                                                Chiyoda  process
                                                sludge  (high sulfate/
                                                sulfite  ratio)
                                                       85-90% solids achieved
                                                                                                                   Ref.  7
                   Comparative laboratory
                   scale
                            Various limestone
                            system sludges
Shawnee sludge:   solids
content increased from
20 to 65%.  Western plant's
sludge:  >  65% solids
achieved
Although  original  water
contents  of sludges were
similar, better results ob-
tained with Western plant
sludge were believed to  be
due  Co its lower water con-
tent  at maximum density
                                       Ref. 38

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 TABLE II-7 (Continued).   SUMMARY OF SLUDGE DEWATERING TECHNIQUES
    Method
Vacuum
Filtration
                       Application
                    Bench-scale
  Sludge
Limestone scrubbing
                                                                                  Results
                                                                                                                Commen t s
                                                                                                                                         Reference
                                                                           65-75% solids achieved
                                                                                                                                           Ref.  38
                    Bench-scale
                                                AMD neutralization
                                                sludge
                           Solids  content  increased
                           from 0.6  to  23%
                              Problems with cake blocking
                              filter were experienced
                                                                                                                                           Ref.  40
                    Bench-scale
                    Pilot-scale;  in
                    conjunction with
                    clarification
                    Full-scale;  in
                    conjunction  with
                    clarification
                                                Pilot plant limestone
                                                scrubbing system
                                                samples
                           55-60% solids  content  was
                           achieved
                              Compare to  38% solids with
                              settling alone.  Thixotropic
                              nature of sludge caused filter
                              cake to rewater upon release.
                              Cake cracking in early stages
                              prohibited  further dewatering.
                              Removal of  cake from filter was
                              difficult
Ref. 7
Ref. 40
Double-alkali system
(General Motors)
53% solids average
                                                                                                                                         Ref. 41
Carbide sludge system
(Louisville Gas and
Electric)•
                                                                           35-45% solids
                                                                                                                                          Ref.  A2
Thermal Drying
                    Commercial
SO. fly ash removal
process
90-95% of original water
content (70%)  removed;
i.e.,  achievement of
90-95% solids  is claimed
                                                                                                                                          Ref.  43

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          Interim Ponding

          An interim pond has three purposes.  It is a clarifica-
tion basin, a sludge dewatering area, and a sludge storage area.
A single pond cannot perform all of these functions effectively.
The effectiveness of ponding as a dewatering technique is a
function of the settling characteristics of the sludge.  This
aspect has been dealt with in Section I-E.

          Clarification (Thickeners)

          Thickeners are currently employed in most sulfur
oxide removal systems as a primary dewatering device in cases
where the solids content is low.  Thickeners are sized in terms
of the surface area per rate of throughput; e.g., if a particular
slurry settles slowly, a longer time and consequently a greater
surface area is required to effectively provide separation of
solids and liquor.   The thickener surface area can vary from
1.0 to 10 m2/metric ton/day (Ref.  14) depending on the settling
characteristics of the sludge.   Limestone scrubber sludges are
reported to thicken well compared to lime sludges because of
the coarse limestone present,  but are associated with a turbid
supernatant.  Therefore, the design should be based on clarifica-
tion considerations.  On the other hand, zone settling rates
should be the basis for design of thickeners for sludges con-
sisting of more uniformly fine particles.

          Thickener underflows for various types of sludges
vary in weight percent solids  and bulk density.   Results have
been reported for a number of  FGD system sludges following 1
day's settling,  and are reproduced below (Ref.  14).   One fly
ash sample is included for comparison.
                              173

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        	Sludge Source	        Wt % Solids
        Eastern Coal (with ash)               <30-45
        Western Coal (no ash)                  21.5
        Dry Injected with
          Wet Scrubbing (with ash)              24
        Limestone Scrubbing (no ash)            39
        Smelter Gas                            37-40
        Fly Ash                                 64

          Cent rifugat ion

          Centrifuges are well-suited for the separation of
waste solids from a liquid suspension.  This technique produces
well concentrated cakes and offers a high degree of effluent
clarification.   Space requirements for equipment are minimal.
However, they have the disadvantage of significant power con-
sumption, and are mechanically complex.

          A conveyor centrifuge can handle large quantities of
solids, but at flow rates no higher than 757 liter/min (200 gal./
min).   The feed should be comminuted or macerated.  The filter
cake is removed by an internal conveyor.  Therefore, the solids
must pack well.   Polymer coagulants must be added to soft
packing solids.

          A two-stage centrifuging. process is advantageous when
there are two types of solids present.  It also provides flexi-
bility against changes in solids quality.

          Centrifugation has been investigated by Dravo,  TVA,
and EPA as a possible dewatering method for sulfur oxide sludges.
A 75 percent solids content was achieved for various pilot plant
samples employing a centrifugal force of 1000 X gravity (Ref. 7).
                               174

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Short-term centrifuge tests conducted at EPA's test facility
at Shawnee produced promising results.  Limestone scrubber
sludges from the clarifier bottoms were used.  The results are
shown in Table II-8 (Ref. 39).  Long-term tests are planned.

          Dravo Corporation conducted a series of tests on lime
scrubbing sludges from Duquesne Light Company's Phillips Station
using a Bird 6-inch continuous centrifuge.  These results are
given in Table II-9 (Ref. 14).

          Because of the blocky physical nature of sulfate
crystals as opposed to sulfite, dewatering is improved by a
higher sulfate/sulfite ratio.  Thus, good results (85-90 percent
solids) have been reported for a sample obtained from the
Chiyoda process, which results in a sludge with an extremely
high sulfate/sulfite ratio.  This process is based on aqueous
scrubbing of S02 to produce sulfurous acid followed by oxidation
to sulfuric acid.  Reaction with limestone at this stage produces
calcium sulfate; thus the sludge contains only negligible amounts
of sulfite.

          Aerospace Corporation has reported the results of a
comparative study of dewatering techniques utilizing clarifier
samples from Shawnee's limestone scrubber.  The water content
of the original sample was ~85 percent; centrifugation reduced
the water content to 44 percent.  Associated bulk densities
were also determined,  and the results are presented in Table
11-10.   A similar study was conducted with clarifier samples
from a Western power plant's limestone scrubber; these results
are also included in Table 11-10.  Although both clarifier
samples contained approximately equal amounts of water,
centrifugation resulted in greater reduction in water content
with the Western plant sample.  The reason suggested for this
was the physical nature of the sludge.  As a result, maximum
                               175

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   Table II-8.  SUMMARY OF SHORT-TERM CENTRIFUGE TESTS AT EPA
               LIMESTONE TEST FACILITY AT SHAWNEE3
Machine Centrifuge Feed Wt 7, Wt % Wt %
Test Speed, Feed Rates Solids Solids Solids in
Series rum Source ecm'5 in Feed in Cake Centrate
I 2000

IId 2000

III 2000

IV 2500

V 2500



HF clarifier 11-22 15-22C 53-57
bottoms
HF clarifier 10-22 16-24° 54-56
bottoms
HF clarifier 10-22 19-29C 58-61
bottoms
HF clarifier 9-33 19-27° 60-63
bottoms
Scrubber 11-35 10-14 59-63
bleed
(clarifier
bypassed)
0.2-0.6

0.3-0.5

0.1-0.5

0.1-1.1

0.1-0.6



aRef.  39
 One gallon is equivalent to 3.785 liters.
°Increase the values by about 3 for pump seal water correction.
'Test Series II was a replicate of Test Series I.
                               176

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                 Table II-9.  CENTRIFUGE TESTS - PILOT PLANT SLUDGE*
                            Bird 6 in. Continuous Centrifuge
                               4130 RPM - 1400 G Force

Run
No.
1
2
3
4
5
6
7
8A
SB
^ef.
Drum
^
Drum
ri_

Feed u j
Materialb>c«d %
Drum 8
Drum 8
Drum 8
Drum 8
(Diluted)
Drum 8
(Diluted)
Drum 8
(Diluted)
Drum 13
Drum 13/14
(50% each)
8A Discharge
14
8: Si02 4%, CaO 43%,
13: Si02 31.8%, CaO 18

Feed
Solids
33.6
33.6
33.8
29.8
20.0
19.5
44.3
42.3
57.4

S 19.9%, S02
.2%, total S

Depth
Pool
Intermediate
Min imum
Maximum
Maximum
Maximum
Minimum
Minimum
Minimum
Minimum

26%, S03 17.2%,
7.5%, S02 8.8%,
Feed
Rate
	 gprn"
3.4
3.4
3.4
3.3
1.1
3.3
3.3
3.3
-

C02 5.8%
S03 8.0%, C02

%
Solids
47.8
48.1
47.3
50.1
50.2
50.2
58.8
55.0
59.5


2.8%

Effluent
Solids %
4.6
0.9
3.4
0.8
0.2
0.6
9.3
13.2
9.2



Drum 14: Not  Identified

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00
         Table 11-10.  COMPARISON OF DEWATERING TECHNIQUES FOR LIMESTONE SCRUBBER SLUDGES3
Technique
Clarification
Settling
Cent rifugat ion
Vacuum Filtration
Shawnee
Bulk Density
(H/cm3)&
1.14 ± 0.02
1.3 + 0.04
1.4 + 0.04
1.6 1 0.05
Samples
% Solids
20 ± 0.5
40 1 0.5
56 + 0.5
64 + 0 . 5
Western Power
Plant Samples
% Solids
^20
(Freely Drained)
>65
>65
            3Ref. 38
            •L                                                               O
             The true density of Shawnee solids is reported to be 2.48 g/cm .

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density of Western sludge  (1.87 g/cm3) is achieved at a slightly
lower water content  (22 percent H20) than for the Shawnee sludge
(1.7 g/cm3 at 30 percent H20).

          Vacuum Filtration

          The most commonly used type of vacuum filter is the
revolving drum.   Some of the variables affecting the ability
to dewater a sludge are:

       Sludge Variables            Operating Variables	
    Concentration of Solids    Vacuum
    Age                        Amount of Drum Submergence
    Temperature                Drum Speed
    Viscosity                  Degree of Agitation
    Compressibility            Filter Media
    Chemical Composition       Prior Conditioning of Sludge
    Nature of Solids

          When vacuum filtration was applied to various pilot
plant limestone sludge samples in TVA labotatories, 55-70 per-
cent solids contents were achieved.  Original solids content
and sulfate/sulfite ratio were not reported.  Typical filtra-
tion rates employed were 2000-2200 liters/hr/m2 (Ref. 7).
These results compared favorably with 38 percent solids obtained
by settling alone.   Considerable problems were encountered,
however, because of the thixotropic nature of the sludge (Ref.
39).   When the vacuum was released, the filter cake rewatered.
Also, cracks formed in the filter cake in early stages of fil-
tration which prohibited further dewatering.  A third problem
of difficult removal of the cake from the filter cloth may
possibly be eliminated by air blast discharge.
                               179

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          Dravo Corporation  (Ref.  14) employed a drum-type
vacuum  filter with a vacuum maintained at 50.8 cm Hg.  They
encountered problems with cracking of the filter cake and con-
sequent disruption of filtration efficiency; this same problem
was observed by TVA.  Cracking tendency varied with the filter
cake  thickness; e.g., a lime scrubbing sludge sample cracked
when  0.95 cm thick.  Another problem observed was the thixo-
tropic nature of the filter cake.  Typical solids content of
the cake was 45-55 percent, but could be increased to 60 percent
with  manipulation.  The thixotropic nature was still retained,
however, since sulfite crystals were present.

          The belt filter is an improved version of the rotary
drum  filter in which the filter medium is removed from the drum
after the dewatering portion of the cycle is completed and passed
over  a small roller to effect cake removal.   The filter medium
has a longer life and is constantly clean for filtration (Ref.
44).

          Pressure Filtration

          After piloting several processes for dewatering
secondary digested sludge, the City of Cedar Rapids,  Iowa,
selected a pressure filter system for its new full scale water
pollution control plant.   Design capacity is about 18 tons/hr
of 48 percent solids from a 5.5 percent solids sludge.   Nine
months'  performance data with both utility fly ash and incinerator
sewage sludge ash,  with and without chemicals,  indicated that
pressure filtration of waste water sludges is an effective  and
economical process.   However, the state of knowledge  for this
technology is still very limited and applicability to scrubber
sludge or other materials is unknown (Ref.  45).
                               180

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          Thermal Drying

          Thermal drying of  sludges is accomplished by the
 introduction of hot gases to remove the moisture from the solid.
 The  four  types of dryers used are fly ash, multiple hearth,
 rotary drums, and atomizing  spray dryers.  All of these units
 are  capable of drying waste water sludges to less than 10 per-
 cent moisture.  However, due to the high fuel requirement,
 thermal drying is economically unattractive compared to other
 methods.  A range quoted for the capital and operating costs
 for  a heat drying sewage sludge treatment is $28-44 dry metric
 ton  (Ref. 40).

          Koch Engineering Company currently markets an S02/fly
 ash  control process involving a unique sludge dehydration opera-
 tion (Ref. 43) in conjunction with a wet limestone or other
 alkali scrubbing system.  The clarifier underflow having a
 typical solids concentration of 30 percent is pumped to the
 dehydrator where atomization occurs via a unique apparatus.  The
 atomized  slurry passes downward concurrently with the hot flue
 gases (~149°C) through the unit.  The water content of the
waste is  reduced by 90-95 percent.  The dry powdered solids are
 removed from the bottom.  Fly ash is also removed along with
 the scrubber solids in this process.

          1.2  Sludge Fixation

          Chemical fixation of scrubber sludge and related
materials is currently being marketed by several commercial
groups including Dravo Corporation, IU Conversion Systems
 (IUCS),  Inc.,  Chemfix Corporation, and Factory Mutual Research
Corporation.   Information available regarding the chemical and
physical nature of lime/limestone scrubber sludge indicates a
need to investigate such stabilization techniques.   Quantitative
                              181

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data describing various properties of untreated scrubber wastes
are presented in other sections of this report.  Basically,  these
data seem to indicate a tendency for untreated, dewatered sludge
to rewater upon contact with an aqueous environment.  In addition,
leaching and permeability features of dried sludges pose potential
environmental hazards.  The ability of proposed fixation tech-
niques to prevent rewatering and leaching from treated sludges
is under investigation.  The current status of the fixation
techniques now being marketed is described here.

          IUCS offers several fixation processes based on the
                                                                 /R\
pozzolanic reaction between fly ash and lime  (Ref. 9).  Poz-0-Pac
the original process on which sulfur oxide sludge fixation tech-
nology was based, has been industrially applied to the stabiliza-
tion of fly ash for production of structural materials.  Three
basic chemical reactions are involved:  (1) the reaction between
the fly ash silica and hydrated lime to form cementitious hy-
drated calcium silicates, tobermorite; (2) the reactions between
soluble salts present in fly ash with lime and the alumina con-
tent of fly ash glass; and (3) aggregate addition resulting  in
mechanical support.

          Poz-0-Tec* is an IUCS commercial process for the
stabilization of fly ash using sulfur oxide sludges in addition
to lime; the end product is called Sulf-0-Poz®.   The chemistry
is reportedly comparable to that describing Portland cement
technology.   Calcium sulfate reacts preferentially with calcium
aluminates or calcium ferrites resulting in hydrated calcium
sulfoaluminates (ettringite) or sulfoferrites, respectively.
                                                            (5)
The cementitious reactions which take place in the Poz-0-Pac
process also are an important feature of the Poz-0-Tec* process.
Sulfite ion, introduced in large quantities as magnesium sul-
fite or calcium sulfite in the sludge, acts as a catalyst in
f\
 A service mark owned by III Conversion Systems, Inc.

                              182

-------
 the  cementitious reactions.  Addition of aggregate may or may
 not  be  required, depending on the characteristics of the start-
 ing  materials  and  the desired strength of the Sulf-0-Poz®
 product.  This product  is primarily a disposal material, but
 in some instances  might be used as a structural material in
 land reclamation projects, structural embankments, etc. after
 a couple of weeks  of curing  (Ref. 45).  Further processing of
 Sulf-0-Poz^ is another  alternative; utilization of the treated
 sludge  as synthetic aggregate or road base material is then
 possible.

          The Poz-0-Tec process can be retrofitted to existing
 power plant scrubber facilities.  Application to most oil-fired
 systems  is not feasible, however, since availability of fly
 ash  is  essential to the process.  Conditions of relatively
 higher pH, as in lime systems compared to limestone, favor the
 reactions, although both types of scrubber sludges can be treated
 by the  IUCS process (Ref. 38).  The presence of soluble magnesium
 compounds introduced as dolomitic limestones is claimed to result
 in faster, stronger reactions because of the higher sulfate
 solubilities.

          The initial step in the Poz-0-Tec process involves
 dewatering of the  sludge by one or more of the techniques dis-
 cussed in the preceding section.  If fly ash is collected dry,
 addition to the sludge at this stage aids in the dewatering.
 If collection is by a wet method, the fly ash slurry may be
 introduced into the primary sludge dewatering device.   The
 sludge/fly ash mixture is then conditioned with make-up additives
which may include additional lime, limestone, fly ash,  bottom
 ash,  other sulfur oxide salts, and optional aggregate or other
waste products.  The output from the mixing and conditioning
 device is reportedly suitable for utilization as a stabilized
                              183

-------
fill material.  The flow diagram for this process is shown in
Figure II-3.  This process is currently being demonstrated at
Southern California Edison's Mohave Station where a full-scale
limestone system is installed.  More information may be found
in Section II-B.  Tests at other sites are being considered.

          The economics of the fixation process offered by IU
Conversion Systems have been presented by company officials
(Ref. 9).  Because of the many factors influencing the actual
costs that would be incurred by a power plant utilizing this
system, the estimated cost cannot be considered typical.   Actual
cost figures for full-scale disposal are not available.

          Those factors affecting the cost of this or any
other fixation process are given below:

          1.  Annual tonnages to be handled by the
              conversion process.

          2.  New boiler installation versus exist-
              ing facilities.

          3.  The type of equipment selected for fly
              ash removal--for example, electrostatic
              precipitators versus  wet scrubbers.

          4.  The chemical analysis of coal--sulfur,
              CaO,  and ash contents.

          5.  Location of plant--on-site versus
              off-site.

          6.  Transportation costs--to and from con-
              version plant.
                              184

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       FLY  ASH
  SULFUR
  OXIDES
UNDERFLOW
                             PRIMARY  DEWATERING
           I	
00
                                                                       MAKE-UP  PROCESS
                                                                           ADDITIVES
       SECONDARY
       DEWATERING
                                                                    •>
  MIXING &
CONDITIONING
*
                                                                                             *
SU-F-O-POZ PRODUCTS
     DAMS
  RESERVOIRS
                                                                       ROAD  BASE
                                                                     STRUCTURAL FILL
                                                                     »••••••••••••• •••
                                                                       AGGLOMERATION
                                                                   •STRUCTURAL PRODUCTS^
                                                                   •   AGGREGATE   •
                                                                   J   CONCRETE    I
                                                                   ^STRUCTURAL SHAPESj
                     Figure II-3.   Schematic Diagram of  Poz-0-Tec  Process  (Ref.  10).

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          7.  Redundancy factor—duplication of
              equipment versus emergency holding
              basins, etc.

          8.  Type of scrubber--limestone versus
              lime.

          9.  Acquisition and cost of land.

         10.  Type of end product selected.

Based on estimates for newly installed plants in the range 1000-
2000 Mw, burning coal with 3-4 percent sulfur and 10-15 percent
ash content, and incorporating a lime or limestone scrubbing
system, the cost estimated by the vendor to convert the sludge
to a disposable Sulf-0-Poz® material is $4.00-5.00/wet ton (50
percent solids).   This cost estimate includes capital invest-
ment and local transport charges (Ref.  32).

          The sludge generated by the limestone wet scrubbing
system installed on a 163 Mw unit at Will County Station is
being disposed of by fixation and landfilling (Refs.  21, 40, 46)
The treatment is based on addition of quicklime and fly ash.
The spent scrubber slurry presently receives only primary de-
watering treatment by clarification, although possible secondary
treatment (such as vacuum filtration or thermal disc drying)
is being considered to reduce the volume of sludge requiring
fixation.  Supernatant is returned to the system via an interim
pond, while the clarifier underflow is pumped directly into a
ready-mix truck in which lime and fly ash are blended with the
sludge to produce a stable landfill material.  This is trans-
ported by the truck to an on-site sealed basin.  After curing
for approximately 1 month, the material is inspected by
                              186

-------
 authorities  for permission for off-site disposal.  Additional
 information  concerning the Will County disposal operation may
 be  found  in  Section II-B.

          A  recent cost estimate made by Commonwealth Edison
 for their Will County Station disposal operation was $8.00-9.00/
 wet ton (50  percent solids) exclusive of capital costs.  The
 utility also reported a worst operating cost of $10/wet ton (50
 percent solids) and a best operating cost of $5.25/wet ton (50
 percent solids).  A target cost of $6.00 to $6.50/wet ton (50
 percent solids) was projected (Ref. 32).  The $8.00-9.00/wet
 ton disposal cost is equivalent to $3.92/ton of coal, 20.lc per
 106 Btu, or  2.13 mills/Kwh (Ref. 18).

          Dravo Corporation also offers a chemical fixation
 process for  lime/limestone scrubbing waste products (Ref. 14).
 The product  is a clay-like substance convenient for disposal.
 Much of their technology has been developed using sludge samples
 obtained at  a pilot-scale lime scrubber operating at Duquesne
 Light Company's Phillips Station.   However,  sludges from ad-
 ditional sources have also been examined.   The testing of their
 process has  involved basic chemical and engineering evaluations
 for the sludge and treated product on a bench-scale level;
 industrial level testing is being conducted, but results are
 not yet available.  The chemistry of the process has not been
 revealed because of current patent applications on the additive,
Calcilox.   The amount of lime-based additive required,  however,
 is  approximately 3-10 percent by weight of the dry sludge solids.

          A Dravo spokesman estimated a typical cost to the
 customer for a pumping operation of <$5.70/wet ton (50 percent
 solids).  This cost includes land acquisition and capital costs,
but it excludes land reclamation costs (Ref. 32).   The capital
                               187

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 costs  involved  are  estimated  at  $30-60 million,  and  the  total
 cost of  disposal  of ash  and sludge  is estimated  to be equivalent
 to  $2-4/ton  of  coal (Ref.  47).

          Dravo evaluated  two approaches to sludge disposal at
 Duquesne Light  Company's Phillips Station.  The  first was  for
 total  disposal  and  consisted  of  taking clarifier bottoms,  barging
 about  60 miles, res lurrying,  treatment, and disposal at  a  Dravo-
 owned  site.  This approach was estimated to cost about $3.8-5.0
 per metric ton  of wet  (30 percent solids) sludge including about
 15 percent fly  ash.  The second  approach was to  design an  on-
 site handling and treatment process for the utility's operation.
 Duquesne selected the  latter  approach and is purchasing  the
 additive from Dravo which is  acting in a consulting capacity.
 A Duquesne spokesman recently estimated the disposal cost  for
 their  trucking  operation involving re-excavation from ponds at
 $7-10/wet ton (50 percent solids).   Their capital cost was
 given  as $124 per Kw (Ref. 19).

          Ohio  Edison has selected Dravo for disposal of the
 sludge generated at the Bruce Mansfield Plant estimated to be
 on line in 1975.  A Dravo estimate for disposal  costs at this
 facility was <$7.15/wet ton (50 percent solids).   The estimate
was based on considerable land acquisition and development and
 includes an 8 mile pumping operation (Ref.  32).   Dravo is  also
 involved in sludge disposal at Southern California Edison's
Mohave Plant.  More details on these applications may be found
 in Section II-B.

          The Chemfix Division of Environmental  Sciences,  Inc.
markets a proprietary fixation process for conversion of various
industrial sludges to stable landfill with at least two inorganic
chemicals,  one  liquid and one powder.   The volume of additive
needed is 10 percent or less of the volume of waste.
                              188

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The system is based on the reactions between soluble silicates
and silicate settling agents which react in a controlled manner
to produce a solid matrix based on tetrahedrally coordinated
silicon atoms alternating with oxygen atoms along the backbone
of a linear chain (Ref. 48).  Polyvalent metal ions react with
Chemfix process chemicals resulting in a stable, conditioned
sludge similar to those of Dravo and IUCS in that soluble con-
stituents would be tied up and a material suitable for landfill
is produced.  Solidification into an inorganic compound is
estimated to occur within 3 days although time can vary with the
system being treated.  The Chemfix process differs from that of
IUCS and Dravo in that it produces a soil-like material that
is permeable.   Additionally, it can be landscaped in a manner
similar to ordinary earth and can be seeded without requiring
top soil.  The other two processes require top soil for the
final landscaping operation.  The process, applied to nonscrubber
sludges,  has produced stable materials.   Chemfix data indicate
that the material produced does not leach chemical constituents
by rainwater at concentrations that exceed the natural back-
ground levels in groundwaters (Ref.  32).   Environmental Sciences
acknowledges that chlorides and other highly soluble inorganic
substances may present difficulties (Ref. 45).   This aspect,
however,  will be discussed under Subsection II-D-2.0, Water
Pollution Aspects of Landfill Disposal.   The general experience
of Chemfix indicates that solidified wastes when "cast" in place
have fairly good load bearing capacities, but remolded wastes
have poor characteristics.  At present,  Chemfix has not con-
tracted with utilities for full-scale scrubber sludge disposal
although their process is being tested on a smaller scale at
EPA's test facility at Shawnee.  The process has been industrially
applied to metal finishing and electronics fabrication wastes
and other types of nonutility industrial problems.
                              189

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           Typical  costs  for  the Chemfix process have been
 quoted  at  $4-5/wet  ton  (50 percent  solids).  This  includes all
 capital expenses and -local transport  costs  (Ref. 32).  A spokes-
 man  for Commonwealth Edison  reported  a Chemfix estimate of $5.90/
 wet  ton (50 percent solids)  for disposal of sludge at their
 Will County Station; this estimate  was exclusive of local trans-
 port and landfill  costs  (Ref.  18).

           Factory Mutual Research Corporation (FMRC) has a
 method  of  fixation of sludge employing the addition- of a polymer
 structure  to the sludge.  No chemical reactions take place.
 The polymer essentially acts as a mechanical structure to thicken
 the sludge.  The chemical reaction  is begun when borax is added
 and causes a reaction within the polymer itself which filters
 out suspended particles as it  shrinks.  The rubbery material
 produced drains to about 50 percent solids and can be compressed
 to 75-80 percent solids.  When added to water, the compressed
 material will fragment with time but will not reslurry (Ref.  49).

          For each of the above processes,  it is claimed that
 soluble components are immobilized  in the treatment process.
 Specific data are reported by  IU Conversion Systems and Chemfix
 and discussed in Subsection II-D-2.0.   No leachate data from
 Dravo Corporation or FMRC are available at this time.

          Comparative evaluations of several of these processes
 are currently being planned or carried out  in the laboratories
 of Aerospace Corporation under contract to  EPA (Contract No.
 68-02-1010) and in an independent study by  Combustion Engineering,
 Inc.   Aerospace plans to have sludge samples obtained from four
 different power plants conditioned by at least two commercial
processes.   Testing of the treated samples  is being performed
by Aerospace to determine the following characteristics:
                              190

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           1.  Soluble components.

           2.  Permeability.

           3.  Water retention.

           4.  Compression strength.

           5.  Bulk density.

           6.  Detoxification assessment, if
              appropriate.

The work includes sampling from TVA's Shawnee Plant and from
SCE's Mohave Station.  Also to be  included are  sludges from a
lime scrubbing system and from a double alkali system.

          A field study of sludge disposal is planned at
TVA's Shawnee Plant under EPA sponsorship where  the Chemfix,
IUCS, and Dravo processes will be evaluated.

          1.3  Sludge Handling

          The handling operations involved in disposing of
treated sludge in landfills may include one or more of the
following:   wet sluicing (or piping) of sludge,  additives, and/
or fly ash; trucking of ash and other fixation additives;
trucking of sludge to landfill site; use of conveyor belts for
sludge transport between dewatering, treating, landfilling,
and/or trucking facilities;  barging; and rail transport.  The
first of these potential operations has been discussed in
Section II-C.   Each of the others is briefly described below
with emphasis placed on any aspects associated with sulfur
oxide scrubber sludge.

                              -191-

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          Transport of sludge to a landfill site via truck is
one of the approaches being considered by utilities if off-site
disposal is used.  Combustion Engineering transported 83 metric
tons of waste sludge from the limestone scrubber at Kansas Power
and Light's Lawrence facility to Dulles Airport in Washington,
D.C., a distance of approximately 2100 km (1305 miles).  Two
types of vehicles, flat- and round-bottomed trucks, were employed
in order to compare the effect of various features on handling
characteristics.  Prior to loading, the untreated sludge had
been stored in a settling pond at the utility site'for 6 months.
It was dredged up and allowed to drain for 24 hours before load-
ing.  At various intervals during the nonstop trip measurements
and samples were taken.   No leakage of sludge was observed
although excess water drained from the tailgate while on the
road.   Unloading difficulties were encountered with the flat-
bottomed trucks; complete removal of the sludge necessitated
manipulation with a backhoe.  The sludge slid out readily,
however,  from the round-bottomed trailers.

          Experience with trucking of sludge from Duquesne
Light Company's Phillips Station has indicated successful
operation with sludge treated with Dravo's additive.  A spokes-
man for Dravo Corporation recently pointed out the fact that
trucking sludge from a large power plant would not be practical,
however,  as it would require 40 truck loads per hour to dispose
of the sludge (Ref.  30).  With this fact in mind, Dravo is
currently testing the possibility of piping a 30-35 percent
solids slurry containing fixation additives to an off-site
landfill.

          The costs associated with truck transport of sludge
are dependent upon wage rates, distance, load limits, and cycle
times.   Figure II-4 depicts typical haul rates of stabilized
material based on the use of 20-ton trucks (Ref.  50).

                              -192-

-------
o
   3.50
   3.00
   2.50 •
  2.00 •
   1.50 •
   1.00 •
BASIS:
   20  TONS/TRUCK
   $0.25/TON LOADING FEE
   10.30/TON FIRST  MILE
  0.50
                    •    ~—•       «	1	1	1—
                    10      15      20      25     30     35
                             DISTANCE  TRUCKED, Miles
                      40     45
—I
 50
         Figure II-4.  Typical Hauling Rates  for Stabilized Fly  Ash
                              Compositions  (Ref.  50).
                                      -193-

-------
          One source, in comparing the economics of piping versus
truck transport, stated that 80 kilometers (about 50 miles)
should be considered the cut-off distance.  For greater distances,
piping appears more economically attractive (Ref. 29).  This
would vary, of course, depending upon the physical properties of
the material to be transported.

         Dravo has estimated that a typical 5 mile haul would
cost about  $0.05/ton mile

          The rental for trucks is an expensive item-.  A spokes-
man for Commonwealth Edison cited $24.00 per hour for a 12 cubic
yard ready-mix truck for use in mixing and hauling their stabi-
lized sludge and $16.00 per hour for a 12 cubic yard dump truck
(Ref. 18).

          Conveyor belts and related bucket elevators are
potential modes of transport for dewatered sludge over short
distances.   Potential areas of use include conveying of dewater-
ed solids to a fixation facility,  lifting of wastes to hoppers
or mixing devices,  and transport of fixed sludge to landfill
sites.   The water content of the sludge is the major factor
determining feasibility of this application.   If the nature of
the sludge is such that water drains in large amounts, precautions
such as installation of troughs below the conveyors must be
taken to avoid potential water pollution problems.

          Other alternate methods  of transporting the waste
from the scrubber site to the ultimate disposal site include
barge and rail.   Both would be feasible where geography and
surrounding environment would permit such application.

          Barge transportation of  sludge, while only feasible
for utilities near navigable waterways, is economically attractive,
                             -194-

-------
The cost for transporting sludge on ordinary barges exclusive
of costs for unloading and loading facilities appears to be
about $0.01 per wet ton mile  (Ref. 30).

          For volumes below about 100 cubic meters (26,000
gallons) per day, trucking or rail becomes more economically
attractive (Ref. 51).  In this case distance should be the basis
for selection:  trucks for distances shorter than 80 km (50
miles) and railways or barges for longer distances.

2.0       Water Pollution Aspects of Landfill Disposal

          In order to predict leachate characterisitcs of a
landfill, it is first necessary to describe the general features
of water movement and geological considerations for this dis-
posal method.  Due to this recent surge of ecological interest
in sanitary landfills utilized for solid waste disposal, there
is an abundance of information available.  Emrich's review of
research in this field presents an overall view of progress
in the following areas (Ref.  52):

          1.   Leachate generation.

          2.   Chemical characteristics of leachate.

          3.   Movement of water in a landfill.

          4.   Effects of topography, geology, soil,
              and groundwater on leachate.

          5.   Leachate or landfill management.

This section will present a discussion of landfill leachate in
general with specific reference to formation, nature, and move-
ment of leachate generated by lime/limestone scrubber wastes.
                              -195-

-------
           The first consideration when looking at the potential
 impact of landfill leachate is the volume of leachate which
 will be produced.  This is a direct function of the amount of
 water reaching the landfill.  There are two possible sources
 of this water:  rainfall and naturally occurring subsurface
 flow through the landfill site.   This second situation occurs
 when the landfill extends below the existing water table.
 Climate obviously will determine the rainfall.   In humid areas
 leachate will be generated in a relatively short period of time;
 however,  leachate formation  may  be  delayed  for years until- field
 capacity  is  reached in semiarid  and arid  regions  (Ref.  52).   In
 general,  the field capacity  of  a landfill is  the water  that  can
 be  retained  indefinitely  against gravitational force.

           Subsurface  flow is a  natural  phenomenon  which can
 seriously interfere with  safe operation of landfills  in two
 ways.   First,  it is a source of  additional  volume  of potentially
 harmful leachate.  The second consideration is that it  can serve
 as  a direct  means of  groundwater contamination.  Prevention  can
 be  effected  by thorough geologic study  of the site beforehand
 and,  if needed,  installation of  rerouting devices  for the  ground-
 water  flow.

           In a similar vein,  coverage of  the  landfill area when
 complete will  greatly  reduce, if not eliminate, the amount of
 leachate produced; this aspect  is discussed in Subsection II-D-
2.2.

           Infiltration  and permeability characteristics of
 landfill material  determine  the  relative  amounts of runoff
 versus  leachate  as well as the leaching rate.  Minnick has looked
 at  the  effect  of  aging  on permeability of fly ash  stabilized
with lime  (Poz-0-PaO  and fly ash stabilized with sulfur oxide
                              -196-

-------
sludges in addition to lime (Poz-0-Tec)  (Ref.  9).   As shown
in Figure II-5, a great reduction in permeability of fly ash
mixtures is reported by inclusion of sulfur oxide sludges.   In
terms of the subject of this report, these results indicate not
only the low permeability values of the  fixed scrubber sludges
(~10-7 cm/sec after 7 days of curing at  38°C (100°F)), but also
the relatively great reduction in permeability compared to
freshly prepared sludge/fly ash mixtures.   This reduction is
on the order of 2 orders of magnitude.  More specific data
obtained with samples of sludge stabilized by IU Conversion
System's process is presented in Table 11-11.   These data were
measured using standard falling head permeability procedures.

          Table 11-12 presents IUCS data for Shawnee limestone
sludge.  Falling head permeability data indicate improvement
during the first month of curing from 10"1* to 10~6 cm/sec.

          Dravo Corporation reportedly has obtained permeability
values ranging from 1 x 10~k cm/sec for remolded material to
1 x 10~8 cm/sec for undisturbed material (Ref. 47).  This is
compared to high quality clays having permeation values of 10"7
to 10~8 cm/sec and fly ash for which a representative range is
10~2 to 10~3 cm/sec.

          Leaching experiments have been performed on various
sludges and processed materials to help in evaluating the
water quality threat from sludge disposal.  Procedures for
leaching experiments will not simulate environmental conditions;
the laboratory conditions are worse than those anticipated in
field applications and should represent a "worst case" example.

          Minnick has presented analytical results obtained by
atomic absorption analysis of leachable ions on selected
                              -197-

-------
    100
(0
I
o
 o
 ilJ
 S
 O
00
4
CC
Ul
Q.
                                     STANDARD FLY ASH M\X
                                     SLUDGE/FLY ASH  MIX
           Figure  II-5.
    Age, Days of Curing at 100°F


Comparison of  Poz-0-Pac and Poz-0-Tec

   Permeability  Values.

            -198-

-------
    Table 11-11.  RESULTS OF TESTS OF SELECTED STABILIZED
             ROAD BASE MIXTURES PREPARED AT DULLES
                  AIRPORT TRANSPO 72 PROJECT3
Moisture
Content,
%
19.4
19.4
20.0
19.8
19.7
20.0
19.1
Dry
Density*,
pcf b
98.8
98.1
98.3
98.2
100.6
98.8
100.4
7 -Day
Falling Head
Permeabilities,
cm/ sec
2.4 x 10"6
N.D.C
2.9 x 10"6
6.5 x 10"6
5.7 x 10"6
1.0 x 10"6
N.D.
a Ref. 9

  One pcf is equivalent to 16,028 g per cubic meter.
p
  N.D. - Not Determined
                              -199-

-------
                      Table 11-12.  LABORATORY RESULTS OF FIXED TVA LIMESTONE SLUDGE ANALYSIS*
O
O
LEACHATE
CONCENTRATIONS ,
b
ppm
Total Alkali
Tot. Dis. Solids
so3
S°4
Cl
Ca
Mg
Al
Fe
Mn
Cu
Zn
Cd
Cr+3
As
Pb
Sn
Hg
PH
AGE OF TEST, days
2
1068
1370
11
45.2
64
268
0.005
2.2
0.02
0.005
0.02
0.005
0.007
0.05
0.01
0.2
0.1
0.01
12.35
4
542~
730
19
41.9
12
220
0.005
3.2
0.01
0.01
0.01
0.01
0.005
0.03
0.01
0.05
0.1
0.01
12.5
6
810
1210
14
36.2
74
235
0.005
11.4
0.01
0.007
0.01
0.005
0.005
0.02
—
0.05
0.05
__
12.1
10
524
770
20
51.0
21
170
0.01
0.95
0.05
0.007
0.02
0.005
0.005
0.02
—
0.05
0.05
__
11.9
14
40
180
10
48.5
16
27.5
—
0.05
0.01
0.005
0.005
0.005
0.005
0.01
—
0.05
0.05
__
10.2
28
40
250
3
43.6
14
20
—
0.1
<0.01
< 0.005
<0.01
< 0.005
< 0.005
<0.01
—
<0.03
<0.1
_^
9.0

PERMEABILITY,
cm/ sec
COMPRESS IVE
STRENGTH, tons/sq ft

0
1 x 10~4
—
AGE OF TEST, days
7
6.5 x 10~5
4.1
14
—
4.7
21
6.2 x 10~6
__
35
5.0 x 10~6
__
            Ref.  32
            Equivalent  to mg/1

-------
 materials subjected to the Poz-0-Tec or Poz-0-Pac^ process
 (Ref. 9).  The tests were conducted by shaking 500 gram test
 specimens for 48 hours in 2 liters of distilled water.  The
 results of those studies are shown in Table 11-13.  When
 leachate from materials treated by the Poz-0-Tec process were
 compared to federal specifications for drinking water standards,
 only manganese greatly exceeded the limits.  It was noted that
 materials not treated by either stabilization process experienced
 much greater leaching phenomena, thus indicating the effective-
 ness of this type of chemical fixation.  In Table 11-13 the
 decrease in total dissolved solids with aging for the Dulles
 cylinder is noteworthy.  An IUCS analysis of leachate from the
 fixed Shawnee limestone scrubber sludge is given in Table 11-12.
 The data show decreased concentrations with time.

           An analysis of a sludge stabilized by the Dravo
 process is given in Table 11-14 for comparison to the other
 leachate analyses.

          The Chemfix process has recently been tested on a
sludge sample from an Eastern coal burning power plant controlled
by a limestone scrubbing system (Ref.  53).  Analyses of the raw
untreated sludge and leachate from the fixed sample were per-
formed.   The results as shown in Tables 11-15 and 11-16 indicate
that the concentrations of reported toxic elements and ions were
reduced in most cases to less than 0.10 ppm.  Copper and lead
concentrations also decreased to this value after the first
leachate portion.   Analysis of chloride was not given.  There
have been reports that Chemfix solids have not retained chlorides,
cyanide, and hexavalent chromium.  These elements may be problem
areas (Ref. 54).
                              -201-

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                           Table 11-13.  ATOMIC ABSORPTION TESTS FOR LEACHABLE IONS ON SELECTED SPECIMENS SUBJECTED TO 48 HOUR  SHAKING TEST3
O
NJ
 I
Concentration, ppm

FEDERAL SPECIFICATIONS - MAXb
Individual Solid Specimen
Dulles Cylinder (13 Days)
Dulles Cylinder (22 Days)
Poz-0-Tec Test Road Core
Poz-0-Tec Test Road Cylinder
Poz-0-Pac Cylinder
Fly Ash Concrete
Cinder Block
Clay Brick
Asphalt Roofing Shingle
A«.f»repate
Argillite
Dolomitic Limestone
Calcitic Limestone
Steel Slag Aggregate
Pumice
Fly Ash Sludge Aggregate
Cement Mortar Balls
Mine Tailings
Loose Powdered Materials
Fly Ash
Portland Cement
Water Samples
Tap Water
Snow Sample from Pittsburgh
Water Supply (Peggs Creek)
PH


9.5
9.5
6.7
9.2
9.3
10.7
8.2
7.3
7.1

6.9
9.75
8.4
10.8
7.1
11.7
9.0
3.95

9.8
12.0

7.5
6.45
7.25
Total
Dissolved
Solids
500

840
620
90
250
150
440
410
110
150

120
96
180
840
120
700
530
130

2900
3700

180
40
316
Sulfate
250

100
120
16
136
44
170
60
28
46

28
8
8
16
< 1
< 1
27
6

1500
200

36
< 1
~
Cl
250

8
12
14
16
26
46
6
12
22

22
18
-
28
10
16
8
2

8
20

76
6
—
Al
None

0.38
0.37
0.03
0.05
0.10
0.22
0.01
0.03
0.01

0.07
0.02
0.02
0.05
0.06
0.03
0.04
0.05

0.11
0.05

0.02
0.06
—
Total
Iron
0.3

0.08
0.08
0.06
0.10
0.25
0.01
0.04
0.10
0.12

0.06
0.36
1.8
0.15
2.2
0.26
0.17
0.15

0.26
0.44

<0.01
0.46
2.9
Mn
0.05

0.18
0.16
<0.05
0.10
<0.05
<0.05
<0.05
<0.05
<0.05

<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05

<0.05
<0.05

<0.05
<0.05
<0.05
Cu
1.0

0.08
0.08
<0.01
0.08
0.08
0.04
<0.01
0.01
<0.01

0.08
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.16

<0.01
<0.01

0.08
<0.01
0.05
Zn
5.0

0.02
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

<0.01
0.02
0.04
0.02
0.03
0.02
0.01
0.02

0.01
<0.01

0.05
<0.01
0.02
Cd
0.01

<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

<0.01
<0.01
<0.01
0.01
<0.01
<0.01
<0.01
<0.01

<0.01
<0.01

<0.01
<0.01
<0.01
Cr+3
0.05

0.02'
<0.01
<0.01
<0.01
<0.01
<0.01
"=0.01
<0.01
<0.01

<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

<0.01
<0.01

<0.01
<0.01
<0.01
As
0.01

0.02*
0.02
<0.01
0.01
0.01
<0.01
<0.01
<0.01
<0.01

<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01

<0.01
<0.01

<0.01
<0.01
<0.01
Hg
0.001

<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001

<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001

<0.001
<0.001

<0.001
<0.001
<0.001
Pb
0.05

0.08
0.09
<0.01
0.01
0.02
<0.01
0.02
•^o.oi
<0.01

<0.01
0.07
0.03
0.01
0.06
0.06
0.03
0.07

0.06
0.04

0.04
0.02
0.02
Sn
None

0.10
0.10
<0.01
•=0.01
•^0.01
<0.01
•=0.01
^.01
^.Ol

<0.01
<0.5
<0.5
<0.05
<0.05
0.5
<0.01
<0.05

<0.5
<0.5

<0.01
<0.01
<0.01
         "Ref. 9.

         Public Health Service Drinking Water Standards.

-------
          Table 11-14.  CHEMICAL CONSTITUENTS OF STABILIZED

               DESULFURIZATION SYSTEM SLUDGE LEACHATEa>b
Constituent
PH
Dissolved salts
Dissolved Si02
Hardness , CaCO-
Fe-H-
Total iron
Ca-H-
Mg-H-
Mn-H-
Na+
Al-HH-
Alkalinity as CaCO-
Cl"
so4=
S00 =
Concentration, mg/1
11.6
590
N.D.C
430
N.D.C
N.D.C
172
0.05
0.03
4
4
140
66
100
92
                                           N.D.C
aRef.  47

 In this leachate analysis, the pH is high but all other criteria
 are within the range of regulatory requirements.
CN.D.  - Not detectable.

                              -203-

-------
              Table  11-15.  CHEMFIX PRELIMINARY LEACHING  STUDY
               LAB LEACHATE OF  2/28/73 FIELD  CHEMFIX PRODUCE
                           ILLINOIS POWER PLANT
                                                 a ,b
                                     Leachate Water
                                                                  PHS Drinking
Constituent
Aluminum (Al)
Cadmium (Cd)
Total Chromium (Cr)
Copper (Cu)
Cyanide (CN~)
Iron (Fe)
Lead (Pb)
Nickel (Ni)
Phenol
Zinc (Zn)
Raw Sludge
1.
1.
0.
9.
< 0.
760
3.
11
0.
29
2
1
8
0
10

7

25

25
<0.10
<0.10
<0.10
<0.25
<0.10
<0.10
<0.25
<0.10
<0.10
<0.10

<
<
<
<
<
<
<
<
<
<

0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
50
10
10
10
10
10
10
10
10
10
10
75
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10
<0.10 •
<0.10 •
<0.10 •
<0.10 <
100 (Added
< 0
< 0
< 0
< 0
< 0
< 0
c 0
< 0
c 0
t 0
.10
.10
.10
.10
.10
.10
.10
.10
.10
.10

0
0
1
0
0
0

0
5
for reference)
__
.01
.05
.0
.01
.3
.05
—
.001
.0
Ref.  48
All  results in ppm,  unless otherwise indicated
Sludge sample from full  scale limestone scrubbing system at Commonwealth
Edison's Will County Station.  Composite material from three disposal cells.
Each 25  in. of leachate water  represents approximately 800  cc of water.
                                      -204-

-------
                  Table 11-16.  CHEMFIX PRELIMINARY LEACHING STUDY, LAB

                        LEACHATE OF 9/14/73 LAB CHEMFIX PRODUCT3'b

Constituent
Arsenic (As)
Cadmium (Cd)
Chloride (Cl~)
Total Chromium (Cr)
Copper
Cyanide (CN~)
Iron (Fe)
Lead (Pb)
Mercury (Hg)
Nickel (Ni)
Phenol
Sulfate (S04=)
Zinc (Zn)
Raw Sludge0
2.2
0.30
—
2.8
1.5
<0.10
120
26
<0.10
3.5
<0.25
> 10,000
16
Leachate
Waterd
<0.10
<0.10
64
<0.25
<0.10
<0.10
< 0.10
< 0.10
< 0.10
< 0.10
< 0.10
400
< 0.10
PHS Drinking Water
Standards (Added for Reference)
0.01
0.01
250
0.05
1.0
0.01
0.3
0.05
—
—
0.001
250
5.0
3 Ref.  55

  All results in ppm
p
  Sludge  sample from a turbulent contact absorber scrubber on a prototype unit (10 Mw)
   in partially closed loop  operation at the TVA Shawnee Power Plant.
d
  Each  25 in.  of leachate represents  approximately  800 cc  of distilled
   water.
                                         -205-

-------
          Joseph Bern from U. S. Utilities Service Corporation
presented leaching test results from 25 sludge samples generated
by lime wet scrubber pilot plant operations at Duquesne Light
Company, Phillips Station, and Ohio Edison Company's Burger
Station.  The samples included raw sludge, treated sludges, and
processed sludges suitable for use as aggregate.  These data
are given in Tables 11-17 through 11-21.

          Table 11-17 shows the chemical analyses of sludge
samples S-l through S-6.  The leachates from the sludge samples
are included in Table 11-18 and are identified as L-l through
L-6.

          Leaching test results for a dewatered and sintered
sludge product are included in Table 11-19.  The samples are
designated as L-7A, L-8A, and L-9A.

          Table 11-20 lists the results from analyses of
samples L-ll through L-20.  Leaching experiments were performed
on three processed sludges of different lime compositions to
generate this data.  In addition, each sample was aged and the
analyses were repeated to show the effect of aging on the
leaching characteristics of the processed material.  Table II-
21 contains more chemical information concerning leachates
from sludges which contain varying amounts of proprietary
additive.

          An examination of the data indicates that solubilities
of heavy metal ions appear to be an inverse function of the pH.
The data also indicate concentrations of heavy metal ions below
the detection limit or effluent standards in most cases.
                             -206-

-------
                     Table 11-17.  SLUDGE ANALYSIS













Parameters
pH
Total Dissolved
Solids (TDS)
Alkalinity
Sulfate (SO )
Total Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Lead (Pb)
Cadmium (Cd)
Mercury (rig)
Manganese (Mn)
Arsenic (As)

i
cd ro
^H ^^
3
60 *
o* u a
e
0 T3
•H l-i
4J CO
3 -0
H C
H Cfl
. P=J cfl' 0 WQ
3 .Cl PL, OTf^
«"°
8 * '

-------
              Table II-18.   LEACHATE ANALYSES  FROM SLUDGE SAMPLES S-l THROUGH S-6a
o
00
Parameter
PH
Total Dissolved
Solids (TDS)
Alkalinity
Sulfate (SO^)
Total Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Lead (Pb)
Cadmium (Cd)
Mercury (Hg)
Manganese (Mn)
Arsenic (As)
ITT 	
7.8


70.0
1783b
0.04
<0.02
0.15b
O.02
<0.05
<0.003
<0.001


171
7.7


60.0
1547 b
0.08
0.02
0.18b
<0.02
<0.05
<0.003
<0.001


L-3
7.9


55.0
1731b
0.06
0.02
0.04
O.02
<0.05
<0'.003
<0.001


L-4
8.6


48.0
1049 b
0.02
0.02
<0.01
<0.02
<0.05
<0.003
<0.001


L-5
11.6


26
1400 b
0.02
0.02
<0.01
<0.02
<0.05
<0.003
<1 ppb
<0.02

L-6
11.7


220
1430b
0.04
0.02
<0.01
<0.02
<0.05
<0.003
<1 ppb
<0.02

       *Ref.  56.

        Exceeds  stream  criteria.

-------
Table II-19.   LEACHATE ANALYSES FROM COMMERCIAL  PRODUCT
      (SINTERED OR ROASTED DEWATERED SLUDGE)3
Parameter
PH
TDS
Alkalinity
Sulfate (S04)
Total Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Lead (Pb)
Cadmium (Cd)
Mercury (Hg)
Manganese (Mn)
Arsenic (As)
aRef. 56.
b_ ,
L-7A
9.5
620
350
120
0.081
0.08
<0.01
<0.01
0.03
<0.01
<0.001
0.80
0.02


L-8A
8.5
840 b
470
108
0.08
0.08
0.02
0.02
0.09b
<0.01
O.001
0.10
0.02


L-9A
9.2
250
34
136
0.10
0.08
0.01
0.01
0.01
<0.01
<0.001
0.10
0.01


                         -209-

-------
                                                 Table 11-20.  LEACHATE ANALYSES

                                           (SINTERED OR ROASTED DEWATERED SLUDGE)
FROM COMMERCIAL PRODUCT

DIFFERENT LIME COMPOSITION

Parameter
pll
TDS
Alkalinity
Sulfate (SO^)
Tot. Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Lead (Pb)
Cadmium (Cd)
Mercury (Hg)
Manganese (Mn)
Arsenic (As)
Penn
DER
Anal-
ysis
L-10
10.25

929°
0.07
<0.01

0.15
0.01
<1 ppb


Sample 1
1 day
L-ll
11.5
692
536
6
0.10
0.08
<0.01
<0.01
0.02
<0.01
< 0.001
<0.05
<0.01
7 days
L-12
11.4
520
470
20
0.15
0.16C
<0.01
<0.01
0.05
<0.01
0.002
<0.05
<0.01
14 days
L-13
11. 0
450
334
0.12
<0.01
0.03
<0.01
0.05
<0.01
< 0.001
<0.05
<0.01
44 days
L-14
10.8
396
222
52
0.12
0.04
<0.01
<0.01
0.02
<0.01
0.004
<0.05
<0.01
Sample 2b
1 day
L-15
11.4
595
960
80
0.14
<0.01
0.02
<0.01
0.03
<0.01
0.004
<0.05
<0.01
7 days
L-16
11.3
480
444
24
0.08
0.04
0.02
<0.01
0.05
<0.01
0.001
0.05
<0.01
14 days
L-17
10.9
432
210
54
0.35
<0.01
<0.01
<0.01
0.05
<0.01
0.001
<0.05
<0.01
Sample 3b
1 day
L-18
11.8
961
1260
60
0.06
0.08
<0.01
<0.01
0.03
<0.01
0.003
<0.05
<0.01
7 days
L-19
11.7
825
24
0.13
0.16°
<0.01
<0.01
0.07
<0.01
0.001
<0.05
<0.01
14 days
L-20
9.6
621
200
0.13
<0.01
<0.01
<0.01
0.02
<0.01
0.002
<0.05
<0.01
K>
(-•
O
 I
         Ref.  56

         Samples  were made  from different  lime mixtures during  the pilot  plant operations.

         Exceeds  stream criteria.

-------
           Table II-21.  PILOT PLANT SLUDGE WITH

         DIFFERENT QUANTITIES OF HARDENING ADDITIVE3'b
Parameter
PH
TDS
Sulfate (S04)
Total Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Lead (Pb)
Cadmium (Cd)
Mercury (Hg)
Manganese (Mn)
Arsenic (As)
L-21
7.9
1168 c
731 c
0.13
<0.10
0.02
<0.20
0.01
<0.01
<0.0005
<0.05
0.085°
L-22
11.0
900°
468 c
0.10
<0.10
0.02
<0.20
0.01
<0.01
MJ.0005
<0.05
0.05
L-23
11.0
924 c
S51C
0.10
<0.10
0.02
<0.20
0.01
<0.01
^0.0005
<0.05
0.01
L-24
7.9
1148 c
740 c
0.10
O.10
0.02
<0.20
0.01
^0.01
<0.0005
<0.05
0.035
L-25
9.7
920 c
490 c
0.10
<0.10
0.02
<0.20
<0.01
^0.01
<0.0005
<0.05
0.045
aRef.  56.

"Plant operated with varying stoichiometric ratios of slaked
 lime.

 Exceeds stream criteria.
                          -211-

-------
          The aging experiments showed an increase in dissolved
solids and sulfates in the sintered  processed sludge.

          2.1  Runoff Considerations

          IU Conversion Systems has performed tests to deter-
mine the extent of dissolution of species associated with fly
ash-stabilized sulfur oxide sludges (Ref. 9).  The experiments
were conducted by allowing 2 liters of deionized water to flow
over the fixed samples and then subsequently collected.  Results
of atomic absorption analyses of this runoff were reported as
shown in Table 11-22.  They were interpreted as providing a
preliminary basis for the effectiveness of the fixation process's
ability to tie up soluble species within the lattice complexes.

          Table 11-23 contains run-off analyses reported by
Joseph Bern (Ref. 56).  The samples were generated by dripping
2000 ml of deionized and distilled water on the sintered and
processed sludge at 1 ml per second.  The water was collected,
filtered, and analyzed.

          2.2  Preventive Measures

          In cases where fixation processes are economically
undesirable,  it may become necessary to examine other alterna-
tives to prevent water pollution.   Methods available to prevent
contamination of surface and groundwaters include landfill seal-
ing, coverage,  and provision of drainage to divert naturally
occurring surface or groundwater flows around the landfill.

          Interception of subsurface flow is achieved by place-
ment of drains  upstream of the entire area of the landfill.
                             -212-

-------
     Table 11-22.  ATOMIC ABSORPTION TESTS MADE ON SURFACE RUNOFF
              OF A STABILIZED FLY ASH/SLUDGE MIXTURE3>b
Parameter
PH
Total Dissolved Solids
Sulfate
Cl
Al
Total Iron
Mn
Cu
Zn
Cd
Cr+3
As
Hg
Pb
Sn
Dulles Cylinder
(13 Days)
7.0
100
26
12
0.10
0.22
< 0.05
< 0.01
< 0.01
< 0.01
<0.01
< 0. 01
< 0. 001
< 0.01
< 0. 01
Dulles Cylinder
(23 Days)
6.9
96
32
18
0.15
0.06
< 0.05
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.001
< 0.01
< 0.01
Sulfite
Beam
7.2
85
8
18
0.13
0.06
0.60
0.12
< 0.01
< 0.01
< 0.01
< 0.01
< 0.001
0.03
< 0.01
3 Ref. 9
With the exception of pH, all values are reported in parts per million
                                  -213-

-------
             Table 11-23.   RUNOFF ANALYSES  FROM SINTERED


                         PROCESSED SLUDGE3'b
Parameter
pH
TDS
Alkalinity
Sulfate (SO^)
Tot. Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Lead (Pb)
Cadmium (Cd)
Mercury (Hg)
Manganese (Mn)
Arsenic (As)
L-7
6.9
96
20
32
0.06
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.001
< 0.05
< 0.01
L-8
7.0
100
ub
26
0.22
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.001
< 0.05
< 0.01
L-9
6.7
90
10 b
16
0.06
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.001
< 0.05
< 0.01
3 Ref.  56

b
 Exceeds stream criteria
                             -214-

-------
These  cut-off drains should be placed at a depth a few meters
below  the bottom of the landfill to keep the groundwater level
low as well as to provide hydraulic gradient for drainage (Ref.
57).

          To prevent infiltration from surface flow, two ap-
proaches can be taken.  One involves providing vertical gravel
or stone paths extending below the level of the bottom of the
landfill through which surface and/or groundwater can quickly
drain.  The second approach involves using a cover material.
This may be a natural material, such as clay or clay loam,  or  an
artificial membrane.  If an impermeable cover is employed, pre-
caution must be taken to allow release of gases to the atmo-
sphere.  In some instances, carbon dioxide produced in a land-
fill has been observed to contaminate groundwater with additional
hardness.

          Landfill sealing is very similar to the practice of
pond sealing discussed in Section II-C.   The sealant can be
any impermeable material such as an asphalt membrane recently
tested at a site near Tullytown, Pennsylvania (Refs. 58, 59).
Many other potential lining materials have been tested in bench-
scale and experimental plot arrangements.   A few of the more
promising of those tested included:

          1.   10 percent bentonite (Wyoming
              clay used for mud drilling)/
              90 percent soil.

          2.   10 percent bentonite/90 percent
              sand.

          3.   10 percent red mud slurry  (a
              bauxite residue)/ 90 percent soil.

                             -215-

-------
          4.  10 percent latex/90 percent soil.

          5.  30 percent asphalt emulsion/70
              percent soil.

          A study was performed to test the feasibility of using
latex as a soil sealant to prevent acid mine drainage seepage
into subterranean abandoned mines (Ref. 60).  Initially, a
variety of latexes were screened in laboratory tests using re-
constructed soil columns.   The most promising latex, a styrene-
butadiene rubber (SBR) latex, was then tested on selected quarter
acre field plots.  In general, the field tests confirmed that
latex does reduce the permeability of soil to water.  However,
the economics are not attractive and most of the latex is
deposited in the top foot of soil where it is subject to damage
by microbiological attack, frost, and surface vegetation.

          In an arrangement where a landfill liner is used, the
leachate is trapped at the bottom.  It can then be collected
and subjected to water treatment, if necessary,  before release
to the surrounding area.

3.0       Land Reclamation Aspects of Disposal Sites

          Certain aspects of land reclamation following abandon-
ment of a landfill site or filled pond used for scrubber sludges
may lead to potential problems.  These aspects may be assessed
by examining the engineering, physical, and chemical natures of
treated and untreated sludge.

          3.1  Moisture Content and Rewatering Characteristics

          One consideration is the tendency of dried scrubber
sludge to absorb water that it contacts.  As discussed in
                             -216-

-------
 previous  sections of  this report, sulfur oxide sludges are
 relatively  difficult  to  dewater.  One sludge sample was observed
 over  a period of several months during which time little or no
 settling  took place after the first 48 hours.  Drainability
 studies conducted by  Aerospace resulted in retention of enough
 water by  dried Shawnee limestone sludge to return to its original
 water content.  The calculated water retention for sludge with
 underdrainage was 51.7 percent (Ref. 38).  Behavior of chemically
 stabilized  sludge samples is expected to be greatly improved
 although  specific tests  for rewatering potential have not been
 reported.   A practical consideration in regard to rewatering
 is that for a thick layer of dewatered sludge, an accumulation
 of a  few  feet of rain might be required for rewatering.  With
 proper design of the  site plus some low permeability cover
 material  (clay, plastic, or treated sludge) even untreated
 sludge might never rewater since the small amount of water col-
 lected during a rain  should be lost by evaporation before the
 next  rain.

          Untreated sludge disposed of in lined ponds may
 present serious land reclamation problems.  The evaporative
water loss, the only mechanism for dewatering in lined ponds,
will be prohibited or greatly reduced in those parts of the
 country where annual precipitation approaches or exceeds annual
 evaporation.  These problems could be avoided by chemical fixation,

          Initial water content and general index properties of
 chemically  fixed sludges will vary widely from test to test as
well as from process to process.   Dry densities of undisturbed
Dravo-stabilized sludges reportedly ranged from 530.5 Kg/m3
(33.1  Ib/cu ft)  to  700.4  Kg/m  (43.7  Ib/cu ft).   Water  contents
ranged from 42 percent solids to 48 percent solids (Ref. 47).
                             -217-

-------
           IUCS manufactures a  substance from sludge which is
 suitable  for road-building.  Its moisture content is reported
 as  19.5-20 percent, and its dry density is 1570-1600 Kg/m3 (98-
 100 Ib/cu ft)  (Ref. 10).

           3.2  Strength of Disposed Material

           A second consideration in land reclamation of sludge
 disposal  areas is the weight which can be supported by the site.
 This factor can be determined by measuring the pozzolanic
 strength,  compaction strength, and penetration resistance of
 the throwaway product.  The strength associated with any land-
 fill or construction material is a function of composition,
 moisture  content, and compacted density.

           Dried untreated scrubber sludge has been shown to be
 capable of supporting a load of 8 psi with water content below
 35  percent based on studies performed by Aerospace on Shawnee
 and Mohave samples.   This is deemed probably safe for equipment
 and personnel (Ref.  38).   Neither sludge examined in this work
 showed any characteristics of pozzolanic strength which would
 lead to increased compressive strength.   These tests have been
 described previously (Section I-E).

           Samples subjected to the IU Conversion Systems
 fixation process have been tested for various strength char-
 acteristics (Ref.  9).   The penetration resistance is a measure
 of the pressure that must be applied in kilograms per square
meter to cause a penetration of 2.54 cm of a needle with cross-
 sectional area of 1.6 x W~5 square  meters.   The effect of
aging on the strength of a Sulf-0-Poz  composition was presented
 in graphical form (Figure II-6).   The results indicate that
completion of curing occurs approximately 16 weeks after mixing.
                              -218-

-------
vo
i
     6000
   01
   o
   co
   s 4000
   UJ
   tr
     2000
                                             NOTE:  OME  PSI IS EQUIVALENT TO 7O3  KG/M2.
                                        —r

                                         8
                                            Age,Weeks
12
16
20
              Figure 11-6.  Penetration Resistance for a Typical Fly Ash/Calcium


                                Sulfate/Lime Mixture (Ref. 9).

-------
When 5x5x5  centimeter cubes of similar composition were
tested for unconfined compressive strength, curing was completed
much sooner (-6 weeks).  Graphical display of results is shown
in Figure II-7.  The moisture content of materials tested was
35 percent.  Individual data points obtained during bench-scale
compressive strength determinations of Sulf-0-Poz® materials
with moisture contents of -20 percent are shown in Table 11-24.
Table 11-25 presents the results of compressive strength deter-
minations for field-tested road base materials.

          Dravo-stabilized sludges were subjected to- direct
shear and triaxial shear testing to develop strength parameters
for embankment design and to evaluate bearing capacity.   The
angle of internal friction for undisturbed and remolded stabilized
materials varied from 37 to 51 degrees; a typical value for a sludge
cured for 30 days was 39 degrees.   Untreated sludge exhibited an angle
of internal friction between 27 and 30 degress.  The strength^
of the stabilized sludge was comparable to that of dense sand and
gravel under static loading conditions while the strength of
the unstabilized sludge was similar to that of medium-dense 
-------
   2000
UJ
K.
1-
w

Ul
>
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                                        Table 11-24.   PHYSICAL PROPERTIES  OF TRANSPO 72 BASE COURSE COMPOSITIONS
 I
NJ
fO
ro
Test
Desig-
nation
2
3
5
6
7
9
10
Moisture
Content
%
19.5
19.4
20.0
19.8
19.7
20.0
19.1
Dry
Density
pcfb
98.8
98.1
98.3
98.2
100.6
98.8
100. 4
Compress ive Strength
at 100°F (psl)c
2 Days
301
267
369
196
333
290
200
14 Days
732
586
630
458
772
761
868
28 Days
881
622
889
490
861
789
1091
California Bearing p
Ratio
Immediate
52
N.D."
27
20
25
90
N.D.
28 Days
543
N.D.
700
460
580
644
N.D.
Falling Head
crmeabilitles (cm/sec)
7 Days
2.4 x 10~6
N.D.
2.9 x 10~6
6.5 x 10~6
5.7 x 10~6
1.0 x 10~6
N.D.
                 a Ref. 10

                   One pcf is equivalent to 16,028 g/ffl

                 c One psl is equivalent to 703  kg/m

                 d N.D. - Not determined

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Table 11-25.
RESULTS OF FIELD TESTS SHOWING COMPARISON OF POZ-0-PAC
      AND POZ-0-TEC FORMULATIONS3
Dry
Density
Description pcf "
Standard Fly Ash Mix (Poz-0-Pac ) 121.2
, Fly Ash/Sludge Blend A (Poz-0-Tec)f 121.4
£ Fly Ash/Sludge Blend B (Poz-0-Tec)f 120.8
Compressive
at 100° F
2 Days
66
348
318
Strength
psi^
7 Days
770
729
746
Strength of Core
From Roadd,psi
4 Weeks
NCPe
NCP
756
6 Weeks
NCP
1034
1089
a Ref. 9
b One pcf is equivalent to 16,028 g/m3
c 2
One psi is equivalent to 703 kg/m
Average temperature during curing period was 10°C
e NCP - No core possible due to insufficient strength
I T>1__J_ A __.J T> __«- J Jnn <- J £J _ J

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                                UNTREATED, CONSOLIDATED UNDER  A
                                VERY  HIGH STRESS  BEFORE  SHEARING
                      30      40      50
                       NORMAL STRESS, psi
80
Figure II-8.  Effect of Percent Dravo  Additive on
                 Shearing Strength  (Ref.  47).
                        -224-

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 c
 o
cc

CT
LJ
I-
UJ
S
O
K
I-
UJ
z
LJ
Q.
                                LIMIT OF  PENETROMETER
 Figure II-9.   Effect  of  Solid Content and Percent
      Dravo Additive  on the Strength (Ref. 47).


                        -225-

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          Untreated  sludges reportedly have very poor dimensional
 stability.  On exposure to drying conditions, shrinkage and
 cracking were observed  (Ref. 38).  Linear shrinkage of 3.7 per-
 cent was measured for Shawnee sludge.  This was found to be a
 function of water content.  This phenomenon can be prevented by
 addition of a pozzolanic material such as is involved in most
 of the stabilization processes now offered.  IUCS has reported
 the results of behavior of Sulf-0-Poz® material molded into
 2.5 x 2.5 x 25 cm bars and cured at 23°C (Ref. 9).  In each
 case, an initial slight expansion was observed; the degree of
 expansion leveled off within 3-4 weeks for low lime 'content
 samples and within 5-6 weeks for high lime samples, with
 respective overall increases in length of ^0.003 and 0.008 cm/
 cm.  Field tests to date have produced good results with regard
 to structural integrity.

          3.3  Support of Vegetation

          An additional factor to be considered in reclamation
 of abandoned scrubber sludge disposal sites is whether growth
 of vegetation can be supported on the area.  At the present time,
no studies are available directly concerning this aspect.
 However,  Chemfix has reportedly grown grass on fixed industrial
waste sludges to which only fertilizer was added (Ref.  48).

E.        OTHER DISPOSAL METHODS

          Another possible option available for disposal of ash
and sludge,  although not under investigation to the same extent
as landfill and ponding, involves direct deposit of the waste
below the surface in subsurface mines.   Deep mine filling has
been used for the disposal of power plant ash as a mine subsidence
prevention technique (Ref.  61).   The ash is sluiced into the
                             -226-

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mine through boreholes.  Normally, gravity is sufficient to
create a flow into the mine.  Pumps and additional boreholes
were provided in case of hole plugging or increased friction
losses.  A dewatering sump and a settling basin were formed by
constructing dams across the mine floor.  Overflow from the
settling basin flows to the sump from which it is pumped to an
above ground basin.  Further details are available in the
literature (Refs.  61, 62).

           The  feasibility of this type of approach is currently
being investigated by the Bureau of Mines for disposal of lime/
limestone scrubber sludges.  The results from this study are not
yet available.  Investigation of this approach may be worth-
while to those utilities to which abandoned deep mines are avail-
able as  potential disposal sites.

          Another alternative which has been proposed is deep-
well injection.   The EPA policy is to review this alternative
on a case by case basis but considers deep-well injection as a
last resort only.   There is no information available related to
its potential use as a scrubber sludge disposal technique.  The
high solids content of the sludge probably would cause rapid
plugging of the subsurface strata, resulting in decreased
permeability and continually diminishing injection rates.   There
may be some very permeable formations where this would not occur.
                             -227-

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 F.         CURRENT EPA R&D PROGRAMS

 1.0        NERC-RTP Programs

           Because of the rapid emergence of lime/limestone wet
 scrubbing  as the near-term dominant desulfurization process,
 the  low percentage of sludge utilization expected  (see Section
 II-A), and a lack of knowledge regarding potential heavy metal
 and  toxic  element involvement in scrubber chemistry, NERC-RTP
 recently initiated activities toward ecologically sound and
 "safe" treatment/disposal of the waste products from non-
 regenerable S02 control processes.

           A contract entitled "Wet Collected Limestone-Modified
 Fly  Ash Characterization and Evaluation of Potentially Toxic
 Hazards" was formalized late in 1972 with the Aerospace Cor-
 poration.  The contract provided for a detailed characterization
 of wet collected limestone-modified fly ash and an evaluation
 of the potential toxic hazards posed in processes that may be
 performed  in subsequent handling, disposal,  or utilization of
 the  sludge.  However, when procurement for the contract was
 initiated, potential utility sources to obtain representative
 sample types were limited; disposal was essentially limited to
 ponding; and commercial acceptability of throwaway processes
 and  the corresponding quantity of material requiring disposal
were unknown.   These factors led to a program of limited scope
with prime ecological emphasis on toxicity.   Since that time,
 additional utility sources using different sorbent/fuel
 combinations and applying other treatment/disposal techniques
have become operative.   These additional combinations with their
 different  elemental compositions and treatment/disposal tech-
niques needed to be taken into consideration.   Although toxicity
was  still  considered important,  toxic element concentrations
                              -228-

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were expected to represent only a very small percentage of the
total quantities of disposal material.  Additionally,  the
alternate disposal technique of chemical treatment (fixation)
of sludge had become of greater interest.   For these reasons
and the current and projected magnitude of the sludge problem,
NERC-RTP initiated an expanded program with Aerospace to allow
a more complete assessment of ecological acceptability, tech-
nical state-of-the-art, and economics for the various treatment/
disposal techniques.  This new expanded program is entitled
"Study of Disposal of By-products from Nonregenerable Flue Gas
Desulfurization Systems."

          The objectives of the expanded program,  which is
currently underway, are to determine ecologically  and economically
acceptable methods for treatment/disposal  of lime/limestone
sludge.   Sample materials, representative  of as many situations
of lime/limestone wet scrubbing process applications as practi-
cable, are being obtained.  In addition, test, operational
and economic  data from a wide variety of  sources  are being
taken into consideration.

          The basic elements of the program are as follows:

          1.  An inventory of sludge components,
              including chemical analysis  of
              various types of sludge and  the raw
                           B
              materials from which they are formed
              (lime or limestone, coal or  oil,
              process water).   Sorbent/fuel com-
              binations being studied are  limestone/
              Eastern and Western coals, lime/
              Eastern coal, and double alkali/
              Eastern coal.
                             -229-

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           2.   An evaluation of the  potential water
               pollution and solid waste problems
               associated with  disposal of  the  sludge,
               including consideration of existing,
               anticipated  or proposed water effluent,
               water  quality and solid waste standards
               or guidelines.   The information will
               assist in the evaluation of  potential
               treatment/disposal  techniques described
               below.

           3.   An evaluation of  treatment/disposal
               techniques with emphasis on ponding
               and "fixed"  and "unfixed" landfill (and
               related land use  applications).   Physical
               analyses  and tests  of various sludges
               are being conducted, including deter-
               mination of  the effects of dewatering,
               oxidation, chemical fixation, and aging
               on stability, compactibility, leach-
               ability of solubles, potential pond
               seepage, potential run-off problems,
               and other disposal considerations.   The
               economics of various treatment/disposal
               combinations are also being studied.

          4.  A recommendation of the best  available
              technology for sludge treatment/dis-
              posal based on the evaluation described
              above.

          The current Aerospace contract  is limited to  the
sampling and analysis of sludges from only  four power plant
                            -230-

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flue gas desulfurization (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 modifi-
cation 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.
                              -231-

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          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.

          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 ponds nearby.  Two ponds will each receive raw lime and
limestone sludge, respectively; one pond will receive chemically
conditioned lime sludge; and two ponds will receive chemically
conditioned (by two different processes) limestone sludge.
Each pond will have a leachate well and a groundwater well.
Tests shall 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 bottom 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.

2.0       NERC-Corvallis Programs

          NERC-Corvallis has initiated a contract with
Aerospace Corporation directed toward determining the implica-
tions 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.  These data will be used to ascertain the water
pollution and reuse potential,  for various plant uses, of
treated and untreated scrubber liquors.
                              -232-

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 3.0        NERC-Cincinnati  Programs

           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
 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
screening 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.
                             -233-

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          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 supernatant treatment, thickening and dewatering, use
of latex as a soil sealant, and technical and economic feasibility
of bulk transport.

          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 determine 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.
                              -234-

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          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.
                             -235-

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G.        REFERENCES

1.        Coal Research Bureau, West Virginia University,
          "Technical and Economic Evaluation of Dewatering, Pro-
          duction of Structural Materials,  and Recovery of Alumina
          from the Limestone Modified Flyash Produced by a Lime-
          stone Wet-Scrubbing Process,"  Final Progress Report,
          Contract EHSD-71-11, Environmental Protection Agency,
          Not Released.

2.        Condry, Linda Z., Richard B. Muter and William F.
          Lawrence, "Potential Utilization of Solid Waste from
          Lime/Limestone Wet Scrubbing of Flue Gases," Coal
          Research Bureau, West Virginia University, Proceedings
          of Second International Lime/Limestone Wet Scrubbing
          Symposium, Volume  I, Environmental Protection Agency,
          June 1972.

3.        Aerospace Corporation, "Technical and Economic Factors
          Associated with Fly Ash Utilization," Prepared for
          Division  of Control  Systems, Office of Air Programs,
          Environmental Protection Agency,  July 26, 1971.

4.        Capp, John P. and John D. Spender, "Fly Ash Utilization,
          A Summary of Applications and Technology," Information
          Circular 8483, Bureau of Mines, U. S. Department of
          the Interior, 1970.

5.        Brink,  Russell H., "Use of Waste  Sulfate on Transpo
          '72 Parking Lot," Third International Ash Utilization
          Symposium, Office of Research and Development, Federal
          Highway Administration, Washington, D. C., March 13-14,
          1973.
                             -236-

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  6.        Slonaker, John F.  and Joseph W. Leonard, "Review of
            Current Research on Coal Ash in the United States,"
            Third International Ash Utilization Symposium, Coal
            Research Bureau, School of Mines, West Virginia
            University, March 13-14, 1973.

  1•        Slack, A. V. and J. M. Potts, "Disposal and Uses of
            By-Products from Flue Gas Desulfurization Processes -
            Introduction and Overview," Presented at EPA Flue
            Gas Desulfurization Symposium, May 14-17, 1973.

  8.         Taylor,  W.  C.,  "Experience in the Disposal and Utili-
            zation of Sludge from Lime/Limestone  Scrubbing Processes,"
            Presented at EPA Flue Gas  Desulfurization Symposium,
            May 14-17,  1973.

  9.         Minnick,  L.  John,  "Fixation and  Disposal  of Flue  Gas
            Waste  Products:   Technical  and Economic Assessment,"
            I.  U.  Conversion  Systems, Inc.,  Presented at EPA  Flue
            Gas Desulfurization Symposium, May  14-17,  1973.

 10.         Minnick, L.  John,  "Multiple By-Product Utilization,"
            Third  International Ash Utilization Symposium, IU
            Conversion Systems, Inc., March  13-14, 1973.

 11.         "Putting Industrial Sludges in Place," Environmental
            Science and Technology. .6(10) October 1972.

12.         Minnick, L. John, "Structural Compositions Prepared
            from Inorganic Waste Products," Presented at the Annual
           Meeting of the American Association of State Highway
           Officials, Miami Beach, Florida, December 5-10, 1971.
                               -237-

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13.        Brackett, C. E., "Production and Utilization of Ash
           in the United States," Third International Ash Utili-
           zation Symposium, Southern Electric Generating Company,
           March 13-14, 1973.

14.        Selmeczi, Joseph G.  and  R. Gordon Knight, "Properties
           of Power Plant Waste Sludges," Third International
           Ash Utilization Symposium, Dravo Corporation and
           Duquesne Light Company, March 13-14, 1973.

15.        Radian Corp., Evaluation  of Lime/Limestone'-Sludge
           Disposal Options. Contract No. 68-02-0046, EPA 450/3-
           74-016, Austin, Texas, 1973.

16.        Ifeadi, C. N. and H. S. Rosenberg, "Lime/Limestone
           Sludge Disposal - Trends  in the Utility Industry,"
           Presented at the Flue Gas Desulfurization Symposium,
           Atlanta, Georgia, Nov. 1974, Columbus,  Ohio, Battelle -
           Columbus Labs, 1974.

17.        Ando,  Jumpei,  "Status  of Japanese Flue  Gas  Desulfuri-
           zation Technology and Utilizing and Disposing of Sulfur
           Products from Flue Gas Desulfurization  Processes in
           Japan," Presented at EPA  Flue Gas Desulfurization
           Symposium, May 14-17, 1973.

18.        Gifford, Don, "A Year of  Calcium Sludge ," in The Problem
           Beyond Removal. Electrical World Engineering Management
           Conference. Waste Disposal in Environmental Systems.  Oct.
           1973. Proceedings. N.Y.,  McGraw-Hill, pp.  369ff.
                               -238-

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 19.         Pernick, Steve L., Jr. and R. Gordon Knight, "Duquesne
            Light Co.  Phillips Power Station Lime Scrubbing Facility,"
            Presented  at  the Flue Gas Desulfurization Symposium,
            Atlanta, Ga., 1974, Pittsburgh, Pa., Duquesne Light Co.,
            1974.

 20.         Personal Communications, Sept. 1973.

 21.         Jones, Julian W. and Richard D. Stern, "Waste Products
            from Throwaway Flue Gas Cleaning Processes - Ecologically
            Sound Treatment and Disposal," Presented at EPA Flue
            Gas Desulfurization Symposium, May 14-17, 1973.

 22.         Swanson, A. E., Testimony, Northern States Power Co.,
            Sherburne County Hearings, Minneapolis, Minn., April 1972.

 23.         Jonakin, J. J., Testimony, Northern States Power Co.,
            Sherburne County Hearings, Minneapolis, Minn., April 1972.

 24.        Van Ness, R. P.,  Louisville Gas and Electric, Private
           Communications,  August 13, 1973,  September  1973.

 25.        Padron,  Robert R.  and Kenneth C.  O'Brien, "A Full  Scale
           Limestone Wet Scrubbing System for the Utility Board of
           the City of Key West,  Florida," Presented at the Second
           International Lime/Limestone  Wet  Scrubbing Symposium,
           New Orleans, La.,  November 8-12,  1971.

26.        Sakanishi, Jun and  Robert  H. Quig,  "One  Year's Performance
           and Operability of the Chemico/Mitsui  Carbide Sludge
           (Lime) Additive S03  Scrubbing System,"  Presented at  EPA
           Flue Gas  Desulfurization  Symposium,  May 14-17,  1973.
                                -239-

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27.        McCarthy, J. H., "Sludge Disposal in Japan," in The
           Problem Beyond Removal, Electrical World Engineering
           Management Conference. Waste Disposal in Environmental
           Systems. Oct. 1973. Proceedings.  N. Y., McGraw-Hill,
           pp. 395 ff.

28.        Thompson, T. L., P. E. Snoek, and E. J. Wasp, "Economics
           of Regional Waste Transport and Disposal Systems," Water-
           1970. CEP Symposium Series 107 (67). 413-22 (1971).

29.        Boettcher, Richard A., "Pipeline Transportation of Solid
           Waste", AIChE Symp. Ser. 122(68). 205-20 (1972).

30.        Lord, Bill, Presentation at Waste Disposal in Utility
           Environmental Systems Conference, Chicago, 111.,
           Oct. 29-31, 1973.

31.        Kumar, J. and J. A. Jedlicka, "Selecting and Installing
           Synthetic Pond Linings," Chem. Enp.  80(3), 67 (1973).

32.        Rossoff, J., et al., "Disposal of By-Products from Non-
           Regenerable Flue Gas Desulfurization Systems,"
           Presented at the Flue Gas Desulfurization Symposium,
           Atlanta, Ga., Nov.  1974, El Segundo, Ca., The Aerospace
           Corp., 1974.

33.        Letter Progress Report, Materials Research & Development,
           EPA Contract 68-03-0230, October 26, 1973.

34.        McLean, D.  D.,  "Subsurface Disposal:  Precautionary
           Measures," Ind. Water Eng. Aug.  1969. 20-21.

35.        Gulf Seal Corp., Private Communication,  Houston, Texas,
           January 7,  1975.

                               -240-

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 36.        Voyer, D. G. and Cluff, C. B., Water Resources Research
           Center, University of Arizona, "Evaluation of Current
           Reactions in Seepage Control," Presented at Symposium on
           Hydrology and Water Resources in Arizona and the South-
           west, May 1972.

 37.        Schwitzgebel, K., Radian Corp., Leaching Tests from
           Sludge Deposits Performed by STEAG-BISCHOFF at Lunen.
           Germany.(Unpublished) August 1973.

 38.        Rossoff, J. and R. C. Rossi, Disposal of By-Products
           from Non-Regenerable Flue Gas Desulfurization Systems;
           Initial Report. EPA-650/2-74-037-a, El Segundo, Ca.,
           Aerospace Corp., 1974.

 39.        Elder, H. W. and P. Stone, "Operability and Reliability
           of the EPA Lime/Limestone Scrubbing Test Facility,"
           Presented at the EPA Flue Gas Desulfurization Symposium,
           May 14-17, 1973.

40.        West Virginia Univ.,  Coal Research Bureau,  Dewatering
           of Mine Drainage Sludge. Water Pollution Control Research
           Series 14010, Morgantown, W.  Va.,  1971.

41.        Dingo, Thomas T.,  "Initial Operating Experiences with a
           Dual-Alkali SOS  Removal System,  Pt. 1,  Process  Performance
           with a Commercial  Dual-Alkali S0a  Removal System,"
           Presented at the Flue Gas Desulfurization Symposium,
           Atlanta,  Ga., Nov.  1974.
                               -241-

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42.        Van Ness, Robert P., "Operational Status and
           Performance of the Louisville FGD System at the Paddy's
           Run Station,-" Presented at the Flue Gas Desulfurization
           Symposium, Atlanta, Ga., 1974,  Louisville Gas  & Electric
           Co., 1974.

43.        Ebasco Services, Inc., Environmental Impact Analysis.
           Milton R. Young Steam Electric Station Center  Unit 2.
           For Minnkota Power Cooperative, Inc. and Square Butte
           Electric Cooperative, Inc., N. Y.,  1973.

44.        Cornell, Conrad F., "Liquid-solids  Separation  in Air
           Pollutant Removal Systems," Preprint 2363, Presented
           at the ASCE National Environmental  Engineering Conv.,
           Kansas City, Mo., Oct. 1974, Salt Lake City, Utah,
           Envirotech Corp., 1974.

45.        "Ford Calls in the Sludge Experts," Business Week, 32
           (30 June 1973).

46.        Gifford, D. C., "Will County Unit 1 Limestone  Wet Scrubber,"
           Presented at the Second International Lime/Limestone
           Wet Scrubbing Symposium, New Orleans, La., November 8-12,
           1971.

47.        Lord, William H., "FGD Sludge Fixation and Disposal,"
           Presented at the Flue Gas Desulfurization Symposium,
           Atlanta, Ga., Nov. 1974, Pittsburgh, Pa., Dravo Corp.,
           1974.

48.        Conner, Jesse R.,  "Ultimate Disposal of Liquid Wastes
           by Chemical Fixation " Presented at the 29th Annual
           Purdue Industrial Waste Conference, West Lafayette,
           Indiana, Pittsburgh, Pa., Chemfix,  Inc.

                                -242-

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 49.        Crowe, James L.,  "Sludge Disposal from Lime/Limestone
           Scrubbing Processes," Preprint 2354, Presented at the
           ASCE Annual & Nat'l Environmental Engineering Conven-
           tion, Kansas City, Mo., Oct. 1974, Chattanooga, Tenn.,
           TVA, 1974.

 50.        Minnick, L. John, "New Dimensions in Ash Handling Due
           to Environmental Systems," in The Problem Beyond Removal.
           Electrical World Engineering Management Conference.
           Waste Disposal in Environmental Systems. Oct. 1973,
           Proceedings. N. Y., McGraw-Hill.

 51.        Burns and Roe, Inc., Steam Electric Power Plants. Develop-
           ment Document for Effluent Limitation Guidelines and
           Standards of Performance, Draft, New York, 1973.

 52.        Emrich, Glover H., "Guidelines for Sanitary Landfills -
           Ground Water and Percolation," Compost Sri Mgy/.Tnno 1972,
           12-15.

 53.        Connor, Jesse R.,  Environmental Sciences, Inc., Private
           Communication, Aug.  20,  1973.

54.        "Truckloads of Land Fill from Waste Sludge," Chem.
           Week 110(4), 41 (1972).

55.        Connor,  J.  R., "Fixation/Solidification of Sludges  from
           Lime-Limestone SOX  Scrubbers," Environmental Sciences,
           Inc.,  Nov.  2,  1973.
                               -243-

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56.        Bern, Joseph, "Probable Environmental Impact from the
           Disposal of Sulfur Removal Sludges Generated by the
           Slaked Lime - Wet Scrubber Process," in Coal Utilization
           Symposium - Focus on S(X, Emission Control. Louisville.
           Ky.. Oct. 1974. Proceedings Monroeville, Pa., Bituminous
           Coal Research, 1974, pp. 198 ff.

57.        Salvato, Joseph A., William G. Wilkie ,  and Berton E.
           Mead, "Sanitary Landfill-Leaching Prevention and Control,"
           J. Water Pollution Control Federation 43 (10),
           2084-2100 (1971).

58.        "Research Seeks New Ways to Seal Landfill Against
           Leaching," Solid Wastes Management March 1971,  18.

59.        "Landfill Sealing is Now Approved Technique," Solid
           Wastes Management 15 (4), 28 (1972).

60.        "Use of Latex as a Soil Sealant to Control Acid Mine
           Drainage," EPA Water Pollution Control Research Series,
           14010EFK, June 1972.

61.        Tonet, Nelson R., "Hydraulic Disposal to Mines,"
           Presented at the ASME-IEEE Joint Power Generation
           Conference,  Pittsburgh, Sept. 27 - Oct. 10, 1970.

62.        Halzel,  George C., "Ash Disposal." Power Eng. 1969
           (June),  44-6.
                                -244-

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              III.  ALTERNATIVE SULFUR BY-PRODUCTS

           As an alternative to recovering flue gas sulfur as a
 throwaway sludge, some fraction of flue gas sulfur will be re-
 covered as potentially saleable products such as sulfur, sulfuric
 acid, gypsum, sodium sulfate,  ammonium sulfate,  and liquid S03„
 The type and quantity of sulfur by-products recovered will depend
 upon the status of the flue gas desulfurization  production
 technology,  various economic and marketing considerations, and
 various environmental considerations.   A discussion of these
 factors along with a comparison of by-product and sludge pro-
 duction is the  subject of this section.

 A.         PRODUCTION TECHNOLOGY

           The status of various flue gas desulfurization processes
 was  discussed in  Section I-A of this report.   A  brief review,
 with emphasis on  the product and the status of the  technology
 required to  produce it,  will be given  in this  section.

 1.0        Wellman-Lord Regenerable FGD

           In  the Wellman-Lord  regeneration step,  the  absorbent
 (sodium  sulfite, bisulfite,  and sulfate)  is heated  in an evapora-
 tion crystallizer to yield a concentrated S02 gas and sodium
 sulfite  crystals which are recycled.  The high purity, high con-
 centration SOS gas  can be further processed to liquid S03, sul-
 furic acid, or sulfur.   Sulfate  formed in the scrubber by oxida-
 tion cannot be economically regenerated and is removed from the
 system by direct purging or  selective crystallization of sodium
 sulfate.

          Sulfuric acid production from S08 is a well established
technology; on the other hand,  the technology for S03 reduction

                               -245-

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to sulfur is still developing, having been commercially operated
in only one plant, a smelter in Canada.  For example, there has
been a significant demonstration of sodium scrubbing/sulfuric
acid production technology in Japan by Mitsubishi Chemical
Machinery (Davy Powergas) at the Japan Synthetic Rubber's Chiba
Plant.  This unit has operated at almost 100 percent availability
during the past 2 years, removing better than 90 percent of the
SOS in the flue gas stream from an oil-fired boiler and producing
high purity sulfuric acid.  In this country EPA is currently
participating in the funding of a Wellman-Lord process installa-
tion on the 115 Mw Northern Indiana Public Service Clompany's
Mitchell Station.  A 1-year demonstration is planned, starting
up in late 1975.  This will be the first application of the
Wellman-Lord process to coal-fired boilers.  The plant will also
demonstrate the technology for reduction of S08 to elemental
sulfur, a step to be carried out by the Allied Chemical process.

          The sodium sulfate by-product of sodium scrubbing
systems can be recovered or reacted with lime to produce gypsum
and sodium hydroxide.  Both operations have been successfully
demonstrated by sodium scrubbing and sodium-based double alkali
plants in Japan.

2.0       Magnesia-Based Processes

          Like the sodium scrubbing processes, the magnesia
scrubbing processes can produce liquid SOg, sulfuric acid, or
sulfur.  In the regeneration step, a sidestream of recycled
slurry (magnesium oxide, sulfite, and sulfate) is sent to a
crystallizer and centrifuge where hydrated crystals of magnesium
sulfite and magnesium sulfate and unreacted magnesium oxide are
separated from the mother liquor.  Mother liquor is recycled to
the scrubber and the centrifuged wet cake is dried in a rotary
                              -246-

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kiln.  Dried anhydrous crystals are sent to a central plant where
they are calcined to recover magnesium oxide and SQ, .

           EPA  has co-funded a full scale Chemico-Basic Chemicals
magnesia scrubbing process installation which was started up in
April  1972 on  a  155 Mw oil-fired unit at Boston Edison's Mystic
Station.   For  about 1 year, various equipment problems were exper-
ienced.  However, during the last several months of this recently
completed  program, the system demonstrated a greater than 90 per-
cent availability to the boiler.  Regeneration of magnesium oxide
and production of sulfuric acid was carried out at Essex Chemical
Company.   A similar system treating 100 Mw (equivalent) side-
stream of  flue gas from a coal-fired boiler has been installed
at Potomac Electric and Power's Dickerson No. 3 Unit.  The plant
is in  initial  start-up operation.

           Sulfur may be recovered from the concentrated sulfur
dioxide stream by reduction with methane, carbon, or carbon
monoxide.    In addition, it may be possible to directly or in-
directly produce elemental sulfur in the calciner by modification
of the operation (Refc  1).  None of these processes has been
applied in conjunction with magnesia scrubbing processes to date.

3.0       Ammonia-Based Processes

          Ammonia scrubbing systems can be operated to yield
ammonium sulfite, bisulfite,  and sulfate, which may be recovered
or regenerated yielding an essentially pure stream of sulfur
dioxide that can be converted either to acid or elemental sulfur
as the situation dictates.   EPA is sponsoring a pilot scale
evaluation of ammonia scrubbing and regeneration at the TVA
Colbert steam plant.   A present trend in ammonia scrubbing
systems is  toward an ammonia-based double alkali system where
the ammonium sulfite/sulfate  solution is reacted with lime or
                              -247-

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 limestone to produce a throwaway sludge similar to that produced
 by a lime/limestone scrubbing system.  As an alternative to
 sludge production, the ammonium sulfite can be oxidized to sul-
 fate prior to reaction with lime or limestone to produce gypsum
 as a by-product.  The production of gypsum from an ammonia
 scrubbing system has been demonstrated in Japan by the Japan
 Iron and Steel Federation.  In this country, TVA is just beginning
 a demonstration of an ammonia-based double alkali system at their
 pilot unit at the Colbert steam plant.

 4.0       Catalytic Oxidation Processes

           The catalytic oxidation (Cat-Ox) process is restricted
 to sulfuric  acid as the product.   The Cat-Ox (Monsanto)  system
 is similar to the contact acid process.   The flue gas is sent
 to a fixed-bed converter where the S0a  is oxidized to S03  in the
 presence of  a vanadium pentoxide  catalyst.  Sulfuric  acid is
 formed by contacting  the S03-rich gas with water  in an absorp-
 tion tower.   The product acid (75  to  85 percent sulfuric acid)
 is cooled and sent  to  storage.

           EPA, Monsanto,  and  Illinois  Power Company have been
 involved in  the  demonstration of  the Cat-Ox process on a 100 Mw
 boiler  at  Wood River,  Illinois.  The plant was originally started
 in September  1972.  Due  to the lack of natural gas  fuel,  the  re-
 heaters  were modified  to  allow the use of  either gas or  oil.
 Performance  criteria were met  in July of 1973.  The system
 has experienced  operating problems including plugging  of the
 catalyst bed with fly ash, catalyst attrition during cleaning,
 and fly  ash buildup in the final mist eliminator.

 5-0       Lime/Limestone Processes

          Lime/limestone processes can be operated to produce
gypsum as a product instead of producing a throwaway sludge.
Production of high purity gypsum requires that particulates be
                             -248-

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efficiently removed upstream of the sulfur dioxide absorber.
The waste slurry stream containing calcium sulfite, calcium
sulfate, and-calcium carbonate or calcium hydroxide is first
oxidized and then treated with sulfuric acid to convert the excess
calcium carbonate or calcium hydroxide to gypsum.  The resulting
slurry is then centrifuged to produce high-grade gypsum contain-
ing 10-15 percent moisture.

          This process has been demonstrated at a number of
plants in Japan and both high-grade gypsum for use in wallboard
production and lower grade gypsum (containing fly ash) for
Portland cement production have been made.  In this country TVA
has tried to oxidize a limestone scrubbing slurry to improve
settling characteristics but to date no attempt has been made to
produce a marketable product.

B.        ECONOMIC AND MARKETING CONSIDERATIONS

          The economic and marketing factors which must be
assessed to determine the market for sulfur by-products include
the present and future uses for the products, the current and
projected supply and demand, the geographical location of the
potential markets, and the quantities which can potentially
be produced by flue gas desulfurization.  In this section the
influence of each of these factors on the potential by-product
markets for sulfur, sulfuric acid, gypsum, sodium sulfate, am-
monium sulfate, and liquid S0a  is discussed as it applies to the
individual by-products.

          Figure III-l, which shows the location of the major
oil- and coal-fired generating stations, is included as an aid
in understanding the geographical significance of the markets
for various products (Ref. 1).
                              -249-

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1-0
On
O
I
                                                                       N>
                                                                          O1
                                                                                ^
                                                 POWER GENERATION SIZE - MEGAWATTS
                                                       o
o  O   O
4"^
                                                  0-  2001- 4001- 6001- 6001-  10,001-
                                                 EOOO  4000 6000  8000 10,000  15,000
                 Figure III-l.   Location of Major  Coal- and Oil-Fired Power Plants

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1.0       Sulfur

          Sulfur is used for a variety of applications; sulfuric
acid represents 85 percent of the elemental sulfur utilization
in the U0S. (Ref. 2).  Table III-l illustrates the uses of
sulfur in all forms for 1968 (Ref. 3).

          The uses of sulfur in the form of elemental sulfur
include the manufacture of chemicals and the manufacture of re-
fined grades of sulfur used in agriculture and in the rubber
industry.

          From 1967 to 1972, the total U. S. production of sulfur
in all forms fluctuated from 9.5 to 10.2 million metric tons
(10.6 to 11.4 short tons) per year (Ref. 4).  The high of 10.2
million metric tons per year was reached in 1972.  Total pro-
duction includes elemental sulfur recovered as by-product from
petroleum refining and natural gas operations, by-product sul-
furic acid from smelting operations, pyrites, and hydrogen sul-
fide and liquid sulfur dioxide recovery.  As a comparison, it
should be noted that the sulfur production rate from one 1000 Mw
flue gas cleaning installation, operating at 70 percent load,
burning 3 percent S coal with 85 percent S08 collection, is ap-
proximately 65,000 metric tons (72.800 short tons) per year.
This represents approximately 0.65 percent of the total annual
U. So consumption of sulfur.

          In the past most of the sulfur produced in the United
States has been obtained from Frasch sulfur mines.  In 1972,
75 percent of the domestic production of sulfur was Frasch
sulfur.  In this country, all of the Frasch sulfur is produced
in Texas and Louisiana.
                              -251-

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     Table III-l.  CONTINGENCY FORECASTS OF DEMAND FOR SULFUR
                (ALL FORMS) BY END USE, YEAR 2000a
                             Quantity, 103 Long Tons
          End Use               U. S. Forecast
                         Demand                  Base
                          1968                   2000
Fertilizers  	 4,550  	 16,800
Inorganic pigments	   500  	
Cellulose fibers (rayon).   570	  2,000
Nonferrous metals (ore
    leaching)	   300  	  1,050
Explosives 	   250  	    875
Iron and steel pickling .   200  	
Petroleum refining 	   180  	    255
Alcohols 	   135  	    470
Pulp and paper 	   540  	  1,900
Other uses 	 1.860  	  6.500
       Total 	 9,085
    a Ref.  3
                              -252-

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          Between 1962 and 1972 the recovery of elemental sulfur
from natural gas and crude oil desulfurization in the United
States increased from 0.9 to 1.9 million metric tons (1 to 2.1
short tons) per year.  This trend is expected to continue
(Ref. 5) with increased recovery of sulfur at refineries antici-
pated due to ever-increasing imports of high sulfur crude oil
and increased demand for low sulfur fuels caused by environ-
mental regulations.

          Any new supplies of by-product sulfur or other com-
pounds from flue gas desulfurization in the utility industry
would probably not be expected to displace recovered sulfur or
by-product sulfuric acid from other industries.  Any market
penetration by the electric utilities would probably be at the
expense of the Frasch producers (Ref. 6).

          The minimum sulfur price required to keep a Frasch
mine in operation is very difficult to estimate.  Each mine is
a unique situation.  Operating costs vary considerably.  Manderson
(Ref. 5) has estimated the manufacturing costs at $7 per long
ton for a low-cost producer, $11 for a medium-cost, and $15 for
a high-cost producer.  Rising fuel costs will certainly inflate
these estimates.  If a 15 percent pre-tax return on fixed in-
vestment is added, these estimates become $10, 15, and 23 per
long ton.  Sales, general, and administrative expenses increase
these to minimum f.Oob,, prices of $14, 19, and 27 per long ton.
The current posted price for crude, bright molten sulfur, ex-
terminal Tampa, Florida, is $28 per long ton  (Ref. 7).  Large
users probably have contracts for considerably lower prices.

          Assuming that Frasch mines would not be closed until
revenues failed to cover cash expenses, and assuming that
Manderson1s estimates of manufacturing cost approximate cash
                              -253-

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 expenses of producing Frasch  sulfur, upper Midwestern utilities
 would have to offer  sulfur at  $11 per long ton delivered in
 Louisiana.  Shipping costs to  Louisiana by barge on the Tennessee,
 Ohio, and Mississippi Rivers  are estimated to be about $6-7 per
 ton.  Using Manderson's estimate of $4 per long ton for sales
 and administrative expense, it appears that upper Midwestern
 sulfur might be sold on the Gulf Coast if essentially no net
 back (no net profit) were required to justify the project  (Ref. 6)
 Utilities located nearer to the Gulf or close to sulfuric  acid
 plants could conceivably realize a positive net back on sulfur
 sales.

          As was mentioned earlier, 85 percent of all  sulfur
 consumed in the United States  is used in the form of sulfuric
 acid.  Sulfur has several advantages over acid as a product for
marketing, including lower cost of storage, higher concentration
 for shipping, better marketing flexibility, and broader spectrum
of use.  It seems likely, however, that costs of by-producing
 sulfur from flue gas desulfurization systems will be higher
than the costs of producing sulfuric acid because of the need
for a reducing agent.  Moreover, the basic economics are question-
able since the sulfur is in the oxidized form in the stack gas
and this is the form (as sulfuric acid) in which most of it is
used.  It is not very cost-effective to oxidize the sulfur com-
pounds in the fuel during combustion,  reduce the resulting sulfur
dioxide back to sulfur,  and then oxidize it again to acid before
use—unless,  of course,  storage and shipping costs are overriding
considerations (Ref.  8).

          In summary, the market for sulfur as a recovery product
from flue gas desulfurization systems  is uncertain at this time.
There is a potential  market for sulfur in the sulfuric acid
industry but  whether  it  is more economical to recover the SOb
as sulfur or sulfuric acid will depend on the process economics
                              -254-

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as they finally develop and the local considerations which will
cause one product to be favored over another.  In addition, the
technology for reduction is not well developed and requires
reducing agents (e.g., natural gas) which are scarce in some
locationso

2.0       Sulfuric Acid

          Sulfuric acid is the most widely manufactured chemical
in the world.  The major end uses for sulfuric acid are summarized
in Table III-2.  As can be seen from the table, over half the
sulfuric acid produced in the United States is used to make
phosphate fertilizers.  The remaining acid is used for a wide
variety of applications ranging from the production of alcohols
to non-ferrous metallurgy.

          According to U. S. Department of Commerce data (Ref. 10),
the total production of sulfuric acid in the United States was
28,200,000 metric tons in 1972.  This total represents an in-
crease of 5.5 percent over 1971 production.  Production has been
increasing about 5 percent per year since 1960.

          Current manufacturing capacity for sulfuric acid is
nearly 36 million metric tons per year with more than half of
the capacity committed to captive use.  As shown in Figure III-2,
states with the largest capacity for acid manufacture include
Florida, Louisiana, Texas, New Jersey, and Illinois (Ref. 1).
A state-by-state breakdown of capacity is shown in Table III-3.

          The U.S. production of by-product smelter acid in 1972
was reported as equivalent to 0.55 million metric tons (0.60
short tons) of sulfur.  Much of the by-product sulfuric acid is
produced in the Western states, but there are three smelters in
                               -255-

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       Table III-2.   SULFURIC ACID END USE PATTERN 1970a
                                                 Thousand
                                                Short Tons
	(100% Basis)
Fertilizer
  Phosphoric acid products                       13,750
  Normal superphosphate                           1,240
Cellulosics
  Rayon                                             520
  Cellophane                                        170
  Pulp and paper                                    600
Petroleum alkylation                              2,400
Iron and steel pickling                             800
Nonferrous metallurgy
  Uranium ore processing                            300
  Copper leaching                                   350
Chemicals
Ammonium sulfate - coke oven
synthetic
chemical byproduct
Chlorine drying
Alum
Capro lac tarn
Dyes and intermediates
Detergents, synthetic
Chrome chemicals
HC1
HF
ILOS
Alcohols
Other chemicals
Industrial water treatment
Storage batteries
Other processing
TOTAL
500
480
190
150
600
260
370
400
100
150
880
1,440
1,800
380
200
140
470
28,640
                             -256-

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K3
Ln
                                                     o O O O O O O
                                                     O. Ml- IOCH- >)01- tOO- 7901. >OO<- JSOI. 4COI.
                                                     »00 <0«0 OCO 100O 1103 JOOO J100 *vOO »OCO
                                                    ooooOO
                                                    500'- >OOU TOOL  1001. »OOI-  IO OOi-
                                                    • bOO 76OO BCOO  IOC9 IO.OOO  3 i. 4CO
                    Figure III-2.    Sulfuric Acid  Manufacturing Capacity  (Ref.  1).

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 Table III-3.  SULFURIC ACID PLANT CAPACITY3
State
Alabama
Arizona
Arkansas
California
Colorado
Delaware
Florida
Georgia
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan

Capacity,
short tons
per day
1,610
2,627
737
6,774
1,483
1,050
23,661
1,369
3,470
6,944
2,066
1,877
747
550
12,600
223
2,260
330
1,301

State
Mississippi
Missouri
New Jersey
New Mexico
New York
North Carolina
Ohio
Oklahoma
Pennsylvania
Rhode Island
South Carolina
Tennessee
Texas
Utah
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Grand total
Capacity,
short tons
per day
1,067
3,303
6,913
446
583
3,480
3,180
630
2,177
50
324
4,421
9,855
2,133
1,983
333
470
67
360
113,454
Ref. 11
                    -253-

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the Eastern United States (one each in Ohio, Western Pennsylvania,
and Tennessee) that affect Eastern markets.  In addition, another
smelter is scheduled to start up in Kentucky in 1976.

          A 1000 Mw generating station operating at 70 percent
load, burning 3 percent sulfur coal, and equipped with a flue
gas desulfurization system recovering 85 percent of the S08
from the flue gas, could produce approximately 200,000 metric
tons (220,000 short tons) of sulfuric acid per year.  This is
equivalent to slightly less than 1 percent of the present capacity
for sulfuric acid production in the United States.

          In the Southwest and Mountain areas the long distance
to adequate markets, the limited acid consumption in these areas,
and the large sulfur dioxide emissions from smelters combine to
make by-product acid production for sale a very dubious pro-
position.  In a study made for EPA by the Arthur G. McKee and
Company (Ref.  12), it was estimated that only about 60-65 percent of
the sulfur dioxide emitted from Western smelters could be sold
as acid [4.5-5.0 million metric tons (4.95-5.5 short tons) per
year],  and that this could be done only if the acid were priced
at $4 per ton.  This leaves the remainder of smelter acid capacity
and all of that from potential flue gas desulfurization plants
in this area as essentially unsaleable.

          Probably the best situation for by-product acid pro-
duction is that in which a process for using the acid is operated
contiguous to the power plant, thus avoiding the cost of shipping
and marketing the acid.  A phosphate fertilizer plant is the most
likely prospect because a great deal of the sulfuric acid con-
sumption is in the fertilizer industry.  Phosphoric acid, triple
superphosphate, and ammonium phosphate are the logical end-
products.
                             -259-

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          An  appropriate  location  for  such a joinder of processes
 is  the  Upper  Midwest, where over half  of  the phosphate fertilizer
 produced  in the  United  States  is consumed and where many of the
 power plants  burning high-sulfur coal  are located.  It should be
 noted,  however,  that there are many drawbacks to  such an arrange-
 ment, the main one being  that  the  sulfuric acid must be used as
 it  is produced (unless  expensive surge storage is installed).
 Thus, the fertilizer facility  would have  to be operated even at
 times when otherwise it would  not  be economical to do so (Ref. 8).
 Alternatives  to  continuing fertilizer  production during the
 period  of reduced fertilizer demand would include:  (1) neutraliz-
 ing the acid, (2) marketing the acid for  other uses (if possible),
 and (3) acid  storage.   Obviously,  the  relative attractiveness of
 these alternatives will depend on  the  length of time of reduced
 demand, local fertilizer and acid marketing conditions, plant
 conditions for neutralization, storage costs, and others.

          A study conducted by TVA for EPA has indicated that
much of the acid producing capacity in an 11-state area from the
 Upper Midwest to the Gulf Coast is old and will soon require re-
 placement, expansion, or the addition of  sulfur abatement equip-
ment which will  increase the producer's cost of acid.   In many
 cases these manufacturers may be willing  to buy sulfuric acid
 from utilities rather than invest in modifications to existing
 equipment (Ref.   13).

          In summary, it appears that there may be an opportunity
 for by-product sulfuric acid from flue gas desulfurization systems
to displace some of the production from elemental sulfur, at
least in the 11-state area considered by TVA in this study
 (Alabama,  Arkansas, Florida,  Illinois,  Indiana,  Kentucky,
Louisiana, Tennessee, Missouri, Ohio,  and Texas).   The high cost
of storage and shipping, and the vagrancies of the market are
                              -260-

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major problems.  The overall problem of marketing sulfuric acid
is quite complicated, too much so for any full treatment in
this report.  The TVA market study for by-product acid funded by
EPA should be useful in evaluating the situation; the TVA power
system was used as an example.  An analysis made of potential
quantity of acid, shipping cost to various points, and the amount
of acid that could be produced and marketed was calculated for
various levels of networks (Ref. 8).

          The base-case market study showed that the most likely
maximum price allowing sale of all the abatement acid produced
by TVA was $8.76 per short ton plus freight.  At $10 per ton,
only about half the acid could be sold; $20 per ton would be a
prohibitive price resulting in no sales.  Adjustments to the
model gave a "most likely" maximum price as $5.99 per ton (Ref. 9),

3.0       Gypsum

          There are three major commercial applications of
gypsum in the United States.  Over 70 percent of the total
gypsum used is consumed in the manufacture of gypsum wallboard
and plaster, 18 to 22 percent is used as a Portland cement re-
tarder, and 7 to 8 percent is used as a source of sulfur in
sulfur deficient soils.

          Table III-4 shows the U. S. gypsum production statistics
from 1962 to 1972.  This table shows that there has been little
growth in gypsum products during the past 10 years.  Production
has remained between 13.6 and 15»4 million metric tons (15 to
17 million tons) per year.  Production increased to 18.2 million
metric tons (20 million tons) in 1972 due to a rapid increase
in construction activity which many economists  expected to
decline in 1973 or 1974.
                               -261-

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                                      TABLE II1-4.  U. S. GYPSUM STATISTICS (Thousands Short Tons)4
                                    1962     1963     1964     1965     1966     1967     1968     1969     1970      1971      1972



       Crude  gypsum mined            9,969   10,388   10,684   10,033    9,647    9,393   10,018    9,905    9,436    10,418   12,367


       Crude  gypsum Imported
 '        for  consumption             5,421    5,490    6,258    5,911    5,479    4,569    5,474    5,858    6,128     6,094    7,718
to
o»
NJ
 1      Total  crude gypsum,
         mined &  imported           15,390   15,878   16,942   15,944   15,126   13,962   15,492   15,763   15,564    16,512   20,085


       Gypsum calcined               8,819    9,181    9,440    9,320    8,434    7,879    8,844    9,324    8,449     9,526   11,984
       aRefs.  14,  15

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           There  is virtually no merchant market in gypsum.
 Gypsum is  mined,  calcined, and sold by  integrated companies.
 Even  imported  gypsum  is usually from captive mines.  In order
 to  interest  the major gypsum companies  in by-product gypsum, it
 would probably have to be priced at $2  to $2.50 per ton in those
 parts of the country  where there are large seams of high-quality
 gypsum.  Where the quality of mined gypsum is low and some
 beneficiation  is  required before processing, it may be possible
 to  obtain  as much as  $3 per ton delivered to a calcining plant
 (Ref.  6).  A preliminary study by TVA suggests that by-product
 gypsum might be sold  for $2.00 per ton, $0.38 per ton less than
 imported and $1.93 per ton less than domestic gypsum.  The study
 further suggests  that by-product gypsum can be shipped via in-
 land  waterways to local facilities for  $0.65 to $7.45 per ton
 cheaper than imported gypsum (Ref. 9).  Thus, there may be some
 potential market  for  gypsum for wallboard manufacture.  On the
 other hand,  before by-product gypsum from flue gas desulfuriza-
 tion  systems could be sold to a wallboard manufacturer, it
 would be necessary to determine if the  gypsum were of wallboard
 quality.  By-product  gypsum from a coal-fired plant, for example,
 might contain  impurities that would affect wallboard manufacture.

          The  Japanese Chiyoda "Thoroughbred 101" process which
 produces wallboard quality gypsum is undergoing testing at a
 Gulf Power Company plant in Florida (Ref.  9).   Start-up was planned
 for March of 1975.

          Another factor affecting the use of by-product gypsum
 concerns the use of gypsum as a source of sulfur in sulfur-
 deficient soils.  However,  almost the entire amount of gypsum
 (1 million metric tons per year out of a total of 1.2 million
metric tons per year)  used for this purpose is consumed in
 California,  far from  the major coal-fired generating centers in
 the East.   Thus, there is little potential for gypsum marketing
 for this purpose,

                              -263-

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          Further accentuating the poor by-product market for
gypsum is the fact that a 1000 Mw generating plant operating at
70 percent load, burning 3 percent sulfur coal, and equipped with
a flue gas desulfurization system removing 85 percent of the
S02 from the flue gas, could produce approximately 0.4 million
metric tons of gypsum per year.  This is 3 percent of the total
gypsum production in the United States.  Thus, although there is
some potential market for by-product gypsum in this country, the
probable upper limit of the potential market is small compared
to the potential by-product production rate.

4.0       Sodium Sulfate

          The two major uses of sodium sulfate are the production
of pulp in the Kraft pulp industry and the production of glass.
The Kraft pulp industry consumes 67 percent of all production.
The glass industry runs a distant second, consuming 12 percent.
Other users of sodium sulfate are the detergent industry, the
dyeing industry, the sponge industry, and other miscellaneous
industries.

          Table III-5 shows the production and consumption
statistics for the sodium sulfate industry  (Ref. 16).  This table
illustrates the lack of any growth trend in sodium sulfate pro-
duction during the 8 years from 1964 to 1971.  The demand is
presently about 1,450,000 metric tons (1.6 million tons) per
year of which about 182,000 metric tons (200,000 tons) per year
is important.

          The supply of sodium sulfate in the United States
falls into two categories, natural and by-product.  Natural
sodium sulfate from California and Utah accounts for 40 percent
of both production and capacity, although no more than 20 percent
                             -264-

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    Table  III-5.   PRODUCTION  STATISTICS  FOR THE SODIUM

                     SULFATE  INDUSTRY
Consumption including
1964
1.56
1968
1.73
1971
1.59
   imports, million tons'
Domestic production,
   million tons3
 1.32
 1.48
1.35
Capacity, million tons'
 1.72
 1.68
1.52
Operating level, % of
   capacity
77.00
88.00     89.00
 (a)  Units  are  short  tons
                          -265-

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of the market is located west of the Rocky Mountains.  The
natural product from Texas accounts for 10 percent of production
capacity; by-product sources, primarily east of the Mississippi
River, account for about 50 percent.  Thus, about half of the Far
West production must cross the Rockies and absorb a freight
penalty of perhaps $10-$15 per ton.

          By-product sodium sulfate is derived from production
of rayon, cellophane, hydrochloric acid, dichromate, phenol,
basic acid, etc.  Production capacity of by-product sodium sul-
fate east of the Rocky Mountains is approximately 818,000 metric
tons (900,000 tons) per year.  The Eastern market is approxi-
mately 1,180,000 metric tons (1,300,000 tons), of which 182,000
metric tons (200,000 tons) is supplied by imports and 182,000
metric tons (200,000 tons) is supplied by Western production.
Recent environmental regulations affecting the rayon industry
could cause the by-product production by this industry to double,
making the section of the country east of the Rockies self-
sufficient with respect to sodium sulfate production (Ref. 16).

          The supply of by-product sodium sulfate to Eastern
markets will be more than ample in the foreseeable future and
that will make it difficult for potential by-product sodium
sulfate from flue gas desulfurization systems to enter the
Eastern markets.

          A 1000 Mw generating plant operating at 70 percent
load, burning 3 percent sulfur coal, and with a flue gas desulfuri-
zation system recovering 85 percent of the S0a, could produce
300,000 metric tons (330,000 tons)  per year of sodium sulfate.
This is equivalent to the present consumption west of the Rocky
Mountains.  Even sodium-based flue gas desulfurization systems
producing sulfuric acid as the primary by-product would produce
                              -266-

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 15,000  and  30,000 metric  tons per year  sodium sulfate  (based
 on  5  to 10  percent of  the sulfur removed being blown down as
 waste sodium  sulfate).  It  is apparent  that  the sale of sodium
 sulfate as  a  primary by-product from flue gas desulfurization
                                     *
 systems is  not  feasible on  a large  scale basis.  Even  secondary
 production  of sodium sulfate may not find an outlet market and
 therefore may have to  be  reacted with lime or limestone for dis-
 posal or sale as gypsum.  Alternatively, the sodium sulfate
 could be discarded at  sea (which is the current practice in
 Japan),  if  this is environmentally acceptable.

 5.0       Ammonium Sulfate

          Essentially  all of the ammonium sulfate consumed in
 the United  States is used in fertilizers, both as a source of
 nitrogen and  as a source  of sulfur.  In fiscal year 1972, the
 U.S.  consumption of ammonium sulfate for direct application in
 fertilizer was about 1.9  million metric tons (Ref. 17).
 Table III-6 shows that, if  anything, the market for ammonium
 sulfate  has decreased  during the past 5 years.

          In  the Eastern  United States, all  of the ammonium
 sulfate  produced is by-product material.  Much of this by-product
 ammonium sulfate is derived from coke ovens.  Other sources of
 by-product ammonium sulfate include acrylonitrile production
 and caprolactam manufacture.  In 1971, U. S. production of by-
 product  ammonium sulfate  from coke ovens was 0.49 million metric
 tons  (0.54 short tons) and  chemical by-product ammonium sulfate
 production was 1.1 million metric tons  (1.21 million short tons)
 for a total of nearly  1.6 million metric tons (1.76 million
 short tons).  If caprolactam manufacture continues to expand as
 it has in the past 3 years, total by-product ammonium sulfate
may soon exceed the total production of ammonium sulfate in
 1970  (Ref.  17).
                               -267-

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            Table III-6.   U.  S.  AMMONIUM SULFATE PRODUCTION AND INVENTORY LEVELS*
ro
en
oo
i
      Production
           Synthetic NH^Sd,
           Coke-oven by-product
           Other by-product  NH..SO,,
           Total production
                                              Quantity,  10 short tons material
                                          1967
             1968
             1969
             1970
1,074
  746
  837
2,657
  895
  716
1.097
2,708
  774
  648
1.157
2,579
  630
  595
1.259
2,484
      Inventory  Levels Total NHi,SOn
           End of year
           High  for  one month
           Low for one month
           Average monthly  level
  474        439        658        615
  474(Dec.)  511(Feb.)  658(Dec.)  735(Feb.)
  223(May)   355(May)   312(July)  588(June)
  355        425        426        644
        lRef. 18

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          Ammonium sulfate is a poor source of nitrogen (21
percent N) compared with ammonium nitrate (33.5 percent N) and
urea  (46 percent N).  Industry prefers to use the higher analysis
fertilizers in order to minimize transportation, storage, and
handling costs per unit of nutrient.  The sulfur content of
ammonium sulfate is important only in those areas where soils
are deficient in sulfur (primarily California and parts of the
Southeastern United States).  For these reasons the use of
ammonium sulfate fertilizers is decreasing.

          It appears that with the lack of growth in demand for
ammonium sulfate, the increased by-product production from coke
ovens and caprolactam manufacture should more than adequately
supply the U. S. consumption.  For this reason by-product pro-
duction from flue gas desulfurization could not expect to com-
pete with existing by-product production for market.

          Further accentuating the poor by-product market for
ammonium sulfate is the fact that a 1000 Mw generating plant
operating at 70 percent load, burning 3 percent sulfur coal,
and equipped with a flue gas desulfurization removing 85 per-
cent of the S0a  from the flue gas, could produce approximately
0.3 million metric tons (0.33 short tons) of ammonium sulfate
per year.   This is roughly 16 percent of the present annual
production.

6.0       Liquid S0a

          Sulfur dioxide is sold for use as a preservative and
bleach in foods, for solvent refining of lubricating oils, for
preparation and bleaching of sulfite pulp and paper stock, for
conversion to sulfur trioxide, and as a disinfectant and fumigant.
It is not feasible to ship sulfur dioxide in the gaseous state;
therefore, the entire merchant market for sulfur dioxide is for
the liquid.

                              -269-

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          Although the markets for liquid S0a are diverse, the
demand is small.  The total U. S. production in 1971 was reported
to be 86,740 metric tons  (95,414 short tons) (Ref. 10).  From
1967 to 1971 production of liquid S0a fluctuated from 75,000 to
92,000 metric tons (82,500 to 101,200 short tons) per year.  The
total reported U. S. production capacity for liquid S0a is re-
ported to be 140,000 metric tons (154,000 short tons) per year.

          There would appear to be no market for liquid S02 as
a by-product from flue gas desulfurization systems.  A 1000 Mw
generating station operating at 70 percent load, burning 3 per-
cent sulfur coal, and equipped with a flue gas desulfurization
system recovering 85 percent of the SOg  from the flue gas, could
produce approximately 140,000 metric tons (154,000 short tons)
of liquid S0a per year.  This is equivalent to the entire present
capacity for liquid S02 production in the United States.

          Liquid SOg  might be an intermediate form for trans-
portation and/or short-term storage.  It retains the flexibility
of being converted to acid when a market exists and to sulfur or
gypsum for disposal during long periods of weak acid markets.
During short periods of weak markets liquid SQ,  could be stored
with approximately the same difficulty of storing ammonia for
later acid production.

C.        ENVIRONMENTAL CONSIDERATIONS

          The various environmental factors which must be con-
sidered in the production of sulfur by-products from utility
plant flue gas desulfurization systems include:   the pollution
potential of the by-product produced, any storage and handling
problems which might ultimately affect the environment, and any
ecological problems associated with disposal of the by-product
in the event that the market fails or becomes inadequate.   In
                              -270-

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 this section each of these factors is  discussed for  each  of  the
 potential sulfur by-products (sulfur,  sulfuric  acid,  gypsum,
 sodium sulfate,  ammonium sulfate,  and  liquid  S0a).

 1.0       Sulfur

           Sulfur as  a by-product from  utility plant  flue  gas
 desulfurization  systems  would be recovered  in the form of a dry,
 yellow crystalline solid.   In this form  sulfur  can be stacked
 above  ground or  in closed buildings for  storage.  It  is virtually
 insoluble in water although there  is some possibility that wind
 and water erosion plus oxidation could produce  acid constituents
 subject  to leaching  if the sulfur  pile is not covered.  Sulfur
 produced by reducing sulfur dioxide to hydrogen sulfjLde and using
 the Glaus process to produce sulfur may  contain up to about 0.0}.
 percent  hydrogen sulfide which could produce  an objectionable
 odor (Ref.  8).   This odor  probably could be easily handled from
 a covered sulfur pile.

           Even where a market is available for  all of the sulfur
 produced by  a flue gas desulfurization system,  storage and handling
 facilities will  be required  to move  the  sulfur  to market.  For
 short-term  storage an  uncovered pile could probably be used with
 few environmental problems.  For longer  term  storage  covered
 sulfur piles or  blocked sulfur storage probably would be adequate.
 The  economics and environmental attributes  of these storage
methods need further evaluation.

 2.0       Sulfuric Acid

          Sulfuric acid produced as a by-product from flue gas
desulfurization will vary in content from 80 to 98 percent HBS04,
and in quality from a high grade water-white acid to a lower
grade acid containing fly ash impurities.  If sulfuric acid
                              -271-

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 is  allowed to  reach  the  environment,  the pollution potential
 is  obviously great.   The main  environmental concern would be
 water  pollution  resulting  from an acid  spill.  Another potential
 pollution  problem  associated with the production of sulfuric
 acid from  the  recovered  sulfur dioxide  would be the SQ, emission
 from the acid  process.   Normally, tail  gases from the acid pro-
 duction portion  of regenerative flue  gas desulfurization systems
 are returned to  the  scrubbing  system  for recovery of the
          Storage and handling should not produce any additional
environmental problems.  It will be necessary to take proper
steps to ensure that no spills occur and to be prepared to
neutralize a spill in the event that one should occur.

          In the event that the market for by-product sulfuric
acid fails, all of the production of sulfuric acid from a flue
gas desulfurization system must be either stored or neutralized
and disposed of.

          Work is under way to determine the best method of
neutralization.  The preferred method, if feasible, is to react
the acid directly with limestone to make a solid gypsum product,
thus avoiding the need for a solids separation step.  The product
slurry should set up in a short time to a solid that can be
handled and piled, but several weeks will be required to attain
complete reaction.  Transfer of the solid to a landfill disposal
area before the reaction is complete could pose an "acid leach"
problem.

          An alternative disposal method involves diluting the
acid,  reacting it with limestone, and separating the solid.
Complete reaction can be obtained in the dilute system,  and the
solids can be washed to remove occluded acid.
                              -272-

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          If sufficient land is available for disposal of the
neutralized acid and if adequate precautions are taken to eliminate
"acid leach" from the landfill, the disposal of neutralized acid
should not pose any serious environmental problems.

3.0       Gypsum

          Gypsum as a by-product from utility plant flue gas
desulfurization systems would be recovered as a fairly fine white-
to-gray crystalline solid containing 10 to 15 percent moisture.
Pure gypsum has essentially no pollution potential, except for
its intermediate solubility.  It dewaters easily and would allow
land reclamation from storage ponds.  However, the liquor as-
sociated with the gypsum recovered from utility plant flue gas
desulfurization systems may be high in dissolved solids similar
to those found in the water associated with the sludge from
lime/limestone flue gas desulfurization systems.  Unless the by-
product gypsum were washed, these dissolved solids in the water
contained by the gypsum would represent a potential run-off and
leaching problem.  Run-off and leaching could occur from by-
product gypsum used as a direct application fertilizer or stored
in piles and ponds for disposal or marketing.

          Washed by-product gypsum should be identical to pure
gypsum relative to environmental problems associated with storage
and handling or disposal.  The wash water may contain excessive
levels of dissolved species, however, which may require treatment.

4.0       Sodium Sulfate

          By-product sodium sulfate from power plant flue gas
desulfurization systems would be recovered as a dry white crystal-
line solid.   The high solubility of sodium sulfate would create
                            -273-

-------
 a potential  water pollution problem if  exposed  to water.   En-
 closed storage and handling facilities  would have to  be provided
 for handling soluble by-product  sodium  sulfate  in order to
 prevent run-off and leaching problems.

           Non-marketable  sodium  sulfate would have  to be  disposed
 of.   The preferred method of disposing  of waste  sodium sulfate
 is to react  a bleed stream  of dilute  sodium  sulfate from  the
 scrubber with lime to produce gypsum  as a throwaway or possible
 saleable product.   The environmental  problems associated  with
 the  disposal  of gypsum have been previously  discussed.  Alter-
 natively,  sodium sulfate  can be  directly discharged to the sea
 as is currently practiced in Japan.

 5.0        Ammonium Sulfate

           Ammonium sulfate  as a  by-product from power plant flue
 gas  desulfurization systems would be  recovered as a very  fine dry
 crystalline  solid.   The high solubility of ammonium sulfate
 would create  a  potential  water pollution problem and  the  fine-
 ness  of the product would create a potential  air pollution
 problem.   Enclosed storage  and handling facilities would  have
 to be  provided  for handling soluble by-product ammonium sulfate
 in order  to prevent run-off and  leaching problems.  Enclosed
 storage  and handling facilities will  also eliminate the potential
 air pollution problem caused  by  the dusting tendency of the very
 fine recovered by-product ammonium sulfate.

           Disposal would be necessary for non-marketable  ammonium-
 sulfate.  The preferred method of disposing of waste ammonium
 sulfate  is to react  a bleed  stream of dilute ammonium sulfate
 from the  scrubber with lime to produce gypsum.  The environ-
mental problems associated with the disposal of the gypsum have
 already been discussed.
                              -274-

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 6.0        Liquid  SO,

           By-product  sulfur dioxide from power plant flue gas
 desulfurization systems would be recovered as a liquified gas.
 This  gas would be stored in tanks and shipped in tank cars.  The
 only  potential pollution would be air pollution caused by S0a
 leaking off  into  the  atomosphere.

           Disposal of unmarketable liquid S03  would be a compli-
 cated process probably resulting in ultimate disposal as gypsum.

           Due to  the  extremely poor market for by-product liquid
 S0a (indicated in the previous section on economic and marketing
 considerations),  it is assumed for the purpose of this discussion
 that  either no by-product liquid S02 will be produced or small
 amounts will be produced captively.  Based on this assumption
 no disposal of liquid S03 is anticipated.

 D.         ECONOMIC AND ENVIRONMENTAL COMPARISON WITH SLUDGE

           In this section a comparison of all the major sulfur
 by-products of flue gas cleaning (sludge, sulfur, sulfuric
 acid, gypsum) will be discussed.  Table III-7 is a comparison
 summary of all sulfur by-products from FGD processes.  Because
 the other by-products have relatively small marketing potential
 and comparatively major disposal problems if not sold (although
most can easily be converted to gypsum), they will not be discussed
 in the remainder of this section.  The discussion relates to the
relative merits of the by-products themselves and disregards the
 state-of-the-art of the processes which produce them.  Additionally,
any discussion of these alternative by-products clearly is de-
pendent on the ultimate costs of the technologies involved, and
local economic,  marketing,  environmental, transportation, and
                              -275-

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                                 Taolc IU-7.  COMPARISON OF ECONOMIC, MARKETING, AND DISPOSAL ASPECTS OF FLUE CAS CLEANING BY-PRODUCTS
By-product
Sulfur
Sulfurlc
Acid
Cypsua
Sodium
Sulf^e
Annual Production
?rosi 1000 Xw Generating
Plant with TOD*.
ir.etric tons/yr
65,300
200,000
351,000
290,000
(Produced by Kellman-
Power Gas process as
a purge equal to
about 5-107. of the
sulfur in the incoming
flue gas)
Current U.S.
Consumption.
metric tons/yr
10,000,000d
28,200,000s
18,000,000f
Mso.ooo8
Current
Market
Price. $/
metric ton
22-31
11-16
3-4
16-27
Maximum
FCD Svsiem
Credit1*.
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 10-307.
of market either
as S or K2S04
since it is
essentially the
sair.e market J
Good
(Excellent chance
of penetrating
757. of market .
Good chance of
penetrating 10-
30X of autet.)
Questionable
(Not demonstrated
that wallboord-
grade gypsum can be
made. All agricul-
tural gypsum used
in California.
Portland cement
gypsum must bo
1/A--2" in
size. By-product
would have to be
palletized.)
Lih'ited
(eastern market
supplied by
present by-product
production.
Western 'market
equal to output
from one 1000 Mw
plant}
Alternatives for
Non-narketable
By-product
Store/dispose
(piles)
Store
Neutralize &
dispose as
gvpsux (piles,
ponds, land-
fills)
Store/dispose
(ponds, piles.
landfills)
Store
Neutralize &
dispose as
gypsum (ponds,
piles, land-
fills)
Product Dispcssl-
Rel.-ted rdva-.ta^es/
Disadvantages' As
Co-.parec to ~r.treat
ed Scrubier Sludze
(1) >\icu. less D-lk
(2) Less soluble
(3) Orv
(4) Po:ercially
f lor-rcsle
(5) Po^e-tisl K2S
odor oro->le-
(6) Porc--.= icl
erosior pr^aleT.
(7) S.sscnpciole to
c~c~.iccl o-.c
biological oxida-
tion.^
Disposal product:
RVPSI.T
(1) Less bulk
(2) F.csicr to
dcwjccr
(1) Less bulk
(2) Easier to
dewater
Disposal produce:
gypsum
(1) Less bulk
(2) Easier to
dewater
 I
to

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                      Taolc  II1-7   (Continued)  COMPARISON" OF ECONOMIC, MARKETING AND DISPOSAL ASPECTS OF FLUE GAS CLEANING  BY-PRODUCTS
 I
NJ
3y-?rodjct
ATJ-.O-.IU.TI
SulfutC

Lic^id
S02

Sludge


Annual Production
Frcr. 1000 >'•? Generating
Plant with FGDa.
r-.cCr.c :ors/yr
270,000

130,000

710,000
(784,000 shore cons)

Current U.S.
Consumption,
natnc tons/yr
2,'.on,oooh

86.7401




Current
Market
Price. $/
metric ton
27-35

X/A




Max imum
FCD Svstem
Cr«ditb.
mills /.PSw-
(1) Leis .i^.k
(2) Easier to
dewater
Disocs.->l product:
2\psi.-i
(1) Loss bjlk
(2) Easier to
dcvater


(1) T.-prsved phy-
sical ^roD-irries
(2) Less soluale
(3) Redjced
perrea'Jilitv i
leschaoilitv
            " 6400 hr/yr operation. 31 S. 0.4 kg coal/tar-hr. 851 SOt renovol efficiency.
              Assuming Ltilii sale of produce  at lowest: market price.
              There are potential  ground and surface water pollution and land wastage/
              f  L 1.iiii.iLLt.n |jrobli-.uH wiLh  uLl  disposal products shown.  UiiLLuuLiid acnibbav
              sludge may have high potential for these problems.
            d
              Ref.
            «Ref.
            «Ref.
            8 kef.
4
1
15
16
17
10

-------
land use considerations.   However, a few general observations
seem to be appropriate:

          1.  If a reliable market exists probably the most
              environmentally attractive sulfur by-products
              are sulfur  and sulfuric acid;  at reasonable prices
              for the saleable product such regenerable processes
              are economically competitive with lime/limestone
              systems.  However,  it should be noted that the
              same quantities of  soluble species which originate
              in the coal would have to be purged from sulfur
              and sulfuric acid producing systems.

          2.  If acid cannot be marketed relatively reliably,
              sulfur and  gypsum storage probably are the most
              attractive  alternatives on an  environmental basis.
              From an environmental viewpoint,  the  only alter-
              native by-products  which can safely be disposed
              of in their natural states are sulfur and gypsum.
              Sulfuric  acid,  sodium sulfate,  and ammonium sul-
              fate would  require  conversion  to  gypsum prior to
              disposal.   Disposing of liquid S0a  in an environ-
              mentally  safe manner could probably not be done
              without conversion  to sulfuric acid with sub-
              sequent neutralization.   Sulfur affects much less
              land (90  percent less land)  and has less water
              pollution potential than sludge (see  Table III-8)
              and has the additional benefit of providing potential
              long-term sales.  Unlike sludge and gypsum,  waste
              sulfur may  have far-term future potential if the
              world sulfur market becomes  supply-limited near
              the turn  of the century as some studies have in-
              dicated (Ref.  19).   Utilities  which had discarded
              sulfur could reclaim it  and  sell  it when the price
                             -278-

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     Table  III-8.  COMPARISON OF THE AMOUNT OF LIMESTONE
        SLUDGE,  SULFUR, AND GYPSUM THAT CAN BE PRODUCED
          BY A  1000 Mw COAL-FIRED GENERATING STATION3
 Sulfur By-Product        Production      Storage Requirements
                       (metric tons/yr)      (cubic meters)

Wet Limestone Sludge        693,000              480,000
  (50% moisture)

Sulfur                       65,300               47,000
  (dry)

Gypsum                      390,000              210,000
  (10% moisture)
  Q
   Assumptions:   6400 hr/yr operation,  3% S,  127o ash,  0.4 Kg coal/
                 kwh, 85% S03  removal efficiency, sulfite/
                 sulfate mole  ratio of 9:1 in the sludge, CaC03/
                 S02  (inlet) mole ratio of 1.2.

  v<                                        33
   Assuming a storage requirement of 0.72 m- /metric ton (23 ft /
                          3                   3
   ton)  for sulfur,  0.69 m /metric ton (22 ft /ton) for sludge,  and
         3                   3
   0.72  m /metric ton (23 ft /ton) for gypsum.
                            -279-

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               and time were right.  This would amount to a
               national stockpile of a strategic manufacturing
               material.  Gypsum also should be preferable to
               sludge but not to sulfur due to volume (Table III-8)
               and physical and chemical properties;  gypsum might
               also be marketed at some later date.

           3.   Sludge is the least attractive by-product unless
               it can be safely disposed of as landfill in an
               economical manner.   If ponding is required without
               treatment much larger masses of much  Less at-
               tractive material must be stored.   This causes a
               land utilization problem and has to be viewed as
               less desirable environmentally than a  much smaller
               pile of sulfur or gypsum.

           It  is  expected that the first alternative  above,  sale-
 able  acid  or  sulfur,  will make up a maximum of 50,000 Mw equiva-
 lents by 1980.   This  corresponds  to approximately 50 percent  of
 today's acid market and approximately  45 percent  of  the expected
 capacity of FGD  in 1980.   Thus, at  least 50,000 Mw equivalents
 of  sulfur  by-products must be stored or disposed  of  (as  sludge
 or  as sulfur/gypsum).   The projection  of current  trends  in  the
 ratio of regenerable  to non-regenerable processes has  already
 been  discussed.  The  relative total  process costs of  lime/lime-
 stone sludge vs. regenerable  sulfur  were also  discussed  earlier.
 At  this point no one  single process  is clearly less expensive
 than  another, although regenerable  systems producing non-sale-
 able  products may  not  be  economically competitive with lime/
 limestone FGD systems.   The important factors  influencing rela-
 tive  cost in declining  order  of importance are:   (1) actual
 sludge disposal costs,  (2) ultimate  sulfur/acid market, and  (3)
 scrubbing process  costs.   Superimposed on these uncertainties  is
 the side variation in power plant conditions (retrofit difficulty,
age,  size,  percent S  in fuel, type and amount of land, local
regulations,  etc.).
                              -280-

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 E.        REFERENCES

 1.  McGlamery, G. G., et al., Conceptual Design and Cost Study.
    Sulfur Oxide Removal from Power Plant Stack Gas.  Magnesia
    Scrubbing-Regeneration;  Production of Concentrated Sulfuric
    Acid.  EPA-R2-73-244.  Muscle Shoals, Ala., TVA, 1973.

 2.  Hatch, Lewis F., "What Makes Sulfur Unique?"  Hydrocarbon
    Proc. 51  (7), 75-78 (1972).

 3.  U. S. Bureau of Mines, Mineral Facts and Problems, 1970,
    Washington, U. S. Dept. of the Interior, Bureau of Mines,
    1970, Bulletin 650, Washington, GPO, 1970.

 4.  U. S. Department of the Interior, Bureau of Mines, Mineral
    Industry Survey, "Sulfur in 1972," Pittsburgh, Pennsylvania,
    1973.

 5.  Manderson, M. C., "World Sulfur Outlook into the Late 1970"s,"
    Presented at the American Chemical Soc. Annual Convention,
    Chicago, Sept.  1970.

 6.  Foster,  J. F.,  et al., Topical Report on Sulfur Markets for
    Ohio Utilities,  Contract No.  68-02-0040, Columbus, Ohio,
    Battelle, Columbus Labs., 1973.

 7.  Chemical Marketing Reporter 204,  35 (30 July 1973).

8.  Slack, A. V.  and J.  M.  Potts,  "Disposal and Use of By-Products
    from Flue Gas Desulfurization  Processes:  Introduction and
    Overview," presented at the Flue  Gas Desulfurization Symposium,
    New Orleans,  La.,  May  14-17, 1973.
                             -281-

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  9.  Bucy, J. I. and P. A. Corrigan, "TVA-EPA Study of the
      Marketability of Abatement Sulfur Products," Presented
      at the Flue Gas Desulfurization Symposium, Atlanta, Ga.,
      Nov. 1974, Muscle Shoals, Ala., TVA, 1974.

 10.  U. S. Department of Commerce, Bureau of Census, Current
      Industrial Report, M28A (71)-14, "Inorganic Chemicals,"
      Washington, D. C., 1972.

 11.  Chemical Economics Handbook,  "Sulfuric Acid," Stanford
      Research Institute,  Dec. 1967.

 12.  McKee,  Arthur G.  and Company,  Systems  Study for Control of
      Emissions,  Primary Nonferrous  Smelting Industry.  3 vols.
      Final Report under Contract PH 86-65-85 to  NAPCA, June 1969.

 13.  Waitzman, D. A., TVA,  Private Communication,  Aug. 1973.

 14.   Bureau of Mines, Minerals Yearbook,  1972.

 15.   Bureau of Mines, Minerals Industry Survey, Gypsum in the
      Fourth Quarter 1972 (March 5, 1973).

 16.   Jacobs Engineering Co., Sodium Sulfate Market Survey.
      Pasadena, California, 1972.

17.  Douglas, Jr., J.  R. and S. L.  Tisdale,  The Ammonium Sulfate
     Situation, Sulphur Inst.  Monographs, No. 1,  Washington, D.  C.,
     Sulphur Inst.,1971.

18.   CIR Sines M 28B,"Inorganic Fertilizer Materials  and Related
     Acids," USDC, Bureau of Census,  Washington,  D. C.
                               -282-

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19.   Farmer,  M.  H.,  and R.  R.  Bertrand,  Long Range Sulfur Supply
     and Demand  Model.  Final Report,  Contract EHSD 71-13, Linden,
     N.  J.,  Esso Research and  Engineering,  1971.
                               -283-

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                                 TECHNICAL REPORT DATA
                          (Please read Instructions on the reverse before completing)
 1 REPORT NO
  PA-650/2-75-010-b
                                                       3 RECIPIENT'S ACCESSION-NO.
 4. TITLE AND SUBTITLE
 Sulfur Oxide Throwaway Sludge Evaluation Panel
    (SOTSEP) Final Report, Volume II--Technical
    Discussion
                                    5. REPORT DATE
                                    April 1975
                                    6. PERFORMING ORGANIZATION CODE
 7 AUTHOR(S)

 Frank T.  Princiotta, SOTSEP Chairman
                                                       8. PERFORMING ORGANIZATION REPORT NO
 9 PERFORMING ORGANIZATION NAME AND ADDRESS
 EPA, Office of Research and Development
 NERC-RTP, Control Systems Laboratory
 Research Triangle Park, NC 27711
                                    10. PROGRAM ELEMENT NO.

                                    1AB013: ROAP 21ACY-030
                                    11. CONTRACT/GRANT NO.
                                    NA (In-house)
 12 SPONSORING AGENCY NAME AND ADDRESS
                                                        13. TYPE OF REPORT AND PERIOD COVERED
                                                        Final
 NA
                                                        14. SPONSORING AGENCY CODE
 5. SUPPLEMENTARY NOTES
 6 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 comprehensive
 discussion of each study area and includes backup information and references for
 the Volume I Summary section.
 7.
                              KEY WORDS AND DOCUMENT ANALYSIS
                 DESCRIPTORS
                       b.IDENTIFIERS/OPEN ENDED TERMS C.  COSATI Field/Group
 Air Pollution
 Sludge Disposal
 Scrubbers
 Flue Gases
  oal
  ombustion
Electric Power Plants
Sulfur Oxides
Dust
Ponds
Earth Fills
Economics
Air Pollution Control
Stationary Sources
Nonregenerable Process
Particulates
Sulfur Byproducts
13B
07A

21B
21D
10B
07B

08H
13C
05C
 8 DISTRIBUTION STATEMENT

 Unlimited
                        19 SECURITY CLASS (This Report)
                        Unclassified
                         21. NO. OF PAGES

                           303
                                           20. SECURITY CLASS (Thispage)
                                           Unclassified
                                                                    22 PRICE
EPA Form 2220-1 (9-73)
                                       -234-

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