EPA-600/2-76-024
February 1976
Environmental Protection Technology Series
                                  REUSE  OF  POWER  PLANT
                       DESULFURIZATION  WASTE WATER
                                     Industrial Environmental Research Laboratory
                                          Office of Research and Development
                                          U.S. Environmental Protection Agency
                                    Research Triangle Park, North Carolina 27711

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               RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:

     1.   Environmental Health Effects Research
     2.   Environmental Protection Technology
     3.   Ecological Research
     4.   Environmental Monitoring
     5.   Socioeconomic  Environmental Studies

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.
                    EPA REVIEW NOTICE

This report has been reviewed by the U.S.  Environmental
Protection Agency,  and approved for publication.  Approval
does not signify that the contents necessarily reflect the
views and policy of  the Agency, nor does mention of trade
names or commercial products constitute endorsement or
recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service. Springfield, Virginia 22161.

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                                EPA-600/2-76-024
                                February 1976
            REUSE OF POWER PLANT

        DESULFURIZATION WASTE WATER
                    by

L. J. Bornstein,  R.  B. Fling,  F.  D.  Hess
        R.  C.  Rossi, and J.  Rossoff

         The Aerospace Corporation
       2350 East  El  Segundo  Boulevard
       El Segundo,  California   90245
            Grant R-802853-01-0
            ROAP No.  R21AZU-025
         Program Element No.  1BB392
      EPA Task Officer:  Dennis Cannon

Industrial  Environmental  Research  Laboratory
  Office of Energy,  Minerals,  and  Industry
      Research Triangle  Park,  NC   27711
                Prepared  for

    U.S.  ENVIRONMENTAL PROTECTION AGENCY
     Office  of  Research and Development
          Washington, DC 20460

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                           CONTENTS


CONCLUSIONS	       1
RECOMMENDATIONS  	       3
1.    INTRODUCTION	       5
      1. 1   Introduction	       5
      1.2   Program Objectives   	       7
      1.3   Study Approach	       7
      1.4   Organization of This Report	       8
2.    SUMMARY	      11
      2. 1   Water Criteria	      11
      2. 2   Power Plant Scrubbing Processes  	      14
      2. 3   Scrubber Liquor Characterization and
           Assessment  .	      20
      2.4   Water Treatment Technology and Costs	      21
3.    WATER QUALITY CRITERIA  	      27
4.    SCRUBBER LIQUOR CHARACTERIZATION	      29
      4. 1   Power Plant Scrubber Liquor Sampling	      29
      4.2   Potential Scrubber Purge Conditions   	      29
      4. 3   Extrapolation of Process Flows	      56
      4.4   Chemical Conditions Affecting Com-
           position of Scrubber Liquors and Water
           Imbalance  	      70
      4.5   Assessment	      73
5.    WATER TREATMENT STUDIES  	      79
      5. 1   Literature and Industry Review	      79
      5.2   Selected Water Treatment Processes	      90
      5.3   Estimated Water  Treatment Costs	      97
                                iii

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                      CONTENTS (Continued)
REFERENCES  	      107

APPENDIX A:  Description of Chemical Analysis
               Techniques	      113

APPENDIX B:  Costing Background Data	      121

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                           FIGURES
2-1.   EPA/TBA Shawnee Steam Plant Typical Flow
       Diagram for Venturi and Spray Tower
       Scrubber System:  8.34 MW Equivalent
       Operation  	      16

2-2.   Schematic of EPA/TVA Shawnee Steam Plant
       Venturi and Spray Tower Scrubber	      17

2-3.   Water Balance for EPA/TVA Shawnee Steam
       Plant Venturi and Spray Tower Scrubber
       System: 8.34 MW Equivalent Operation  	      18

2-4.   Water Balance for Venturi and Spray Tower
       Scrubber System	      19

2-5.   Estimated Costs of Lime-Soda Softening and
       Filtration	      25

2-6.   Estimated Costs of Lime-Soda and Filtration
       Pretreatment Plus  Reverse Osmosis  	      26

4-1.   Schematic of EPA/TVA Shawnee Steam Plant
       Venturi and Spray Tower Scrubber	       34

4-2.   Typical Flow Diagram for EPA/TVA Shawnee
       Venturi and Spray Tower Scrubber System:
       8.34 MW Equivalent Operation   	       35

4-3.   Water Balance for EPA/TVA Shawnee Venturi
       and Spray Tower Scrubber System:  8. 34 MW
       Equivalent Operation	       39

4-4.   Schematic of EPA/TVA TCA Scrubber  	       40

4-5.   Typical Flow Diagram for EPA/TVA Shawnee
       TCA Scrubber System:  6.8 MW Equivalent
       Operation	       41

4-6.   Water Balance for EPA/TVA Shawnee TCA
       Scrubber System:  6.8 MW Equivalent
       Operation  	       45

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                       FIGURES (Continued)
4-7.   Schematic of Arizona Cholla Station FDS
       and Packed Absorption Tower Scrubber	       46

4-8.   Typical Flow Diagram for Arizona Public
       Service Cholla FDS and Packed Absorption
       Tower Scrubber System: 115 MW
       Equivalent Operation	       48

4-9.   Water Balance for Arizona Cholla Public
       Service FDS and Packed Absorption Tower
       Scrubber System:  115 MW Equivalent
       Operation  	       51

4-10.  Typical Flow Diagram for Duquesne Phillips
       Single-Stage Scrubber System	       53

4-11.  Typical Flow Diagram for Duquesne Phillips
       Station Dual-Stage Scrubber System	       54

4-12.  Schematic of Duquesne Phillips Station
       Single-Stage Scrubber  	       55

4-13.  Water Balance Duquesne Phillips Station
       Single- and Dual-Stage Venturi Scrubber
       Systems:  120 MW Equivalent Operation  	       59

4-14.  Water Balance for Venturi and Spray Tower
       Scrubber System (Extrapolation Based on
       EPA/TVA Shawnee Steam Plant Type of
       Process): 1000 MW Equivalent Operation	       61

4-15.  Water Balance for TCA Scrubber System
       (Extrapolation Based on EPA/TVA Shawnee
       Steam Plant Type of Process):  1000 MW
       Equivalent Operation	       62

4-16.  Water Balance for FDS and Absorption Tower
       Scrubber System (Extrapolation Based on
       Arizona Cholla Public Service Process):
       1000 MW Equivalent Operation   	       63
                               vi

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                       FIGURES (Continued)
4-17.  Water Balance for Dual-Stage Venturi Scrubber
       System   (Extrapolation Based on Duquesne
       Phillips Station Type of Process): 1000 MW

5-1
5-2.
5-3.


Estimated Water Treatment Costs per
Estimated Water Treatment Costs per
Kilowatt Hour for Power Output of 1000 MW 	
65
. . 98
99
100
5-4.   Estimated Water Treatment Costs per
       Million Btu Heat Input for Power Output of
       1000 MW	     101

5-5.   Estimated Water Treatment Costs per Ton
       of Coal Burned for Power Output of  1000 MW	     10Z
                                vii

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                             TABLES
 1-1.   Power Plants Scrubbers Sampled
 2-1.   Water Quality Criteria and Range of
       Concentration of Constituents in Scrubber
       Liquors Studied  	       13

 2-2.   Summary of Generic Types of Water
       Treatment Processes  Capable of Meeting
       Water Quality Criteria	       22

 4-1.   Power Plants Sampled	       29

 4-2.   Test Conditions for EPA/TVA Shawnee
       Venturi and Spray Tower Scrubber	       36

 4-3.   Analyses of Scrubber Liquors from EPA/TVA
       Shawnee Venturi and Spray Tower Scrubber
       System  	       37

 4-4.   Test Conditions for EPA/TVA Shawnee
       TCA Scrubber   	       43

 4-5.   Analyses of Scrubber Liquors from EPA/TVA
       Shawnee TCA Scrubber System  	       44

 4-6.   Operating Conditions for Arizona Public
       Service Cholla  FDS and Absorption Tower
       Scrubber System	       49

 4-7.   Analyses of Scrubber Liquors from Arizona
       Public Service  Cholla FDS and Absorption
       Tower Scrubber System	       50

4-8.   Operating Conditions for Duquesne Phillips
       Station: Single- and Dual-Stage Venturi
       Scrubber Systems 	       57

4-9.   Analyses of Scrubber Liquors from Duquesne
       Phillips Station:  Single- and  Dual-Stage
       Venturi Scrubber Systems  	       58
                                viii

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                       TABLES (Continued)
4-10.  Summary and Comparison of Water Balance
       Projections for 1000 MW Equivalent Scrubbers	      66

4-11.  Summary of Scrubber Bleed Stream Flow
       Projections for 1000 MW Equivalent Scrubbers	      68

4-12.  Potential Water Uses and Constituents of
       Concern  	      75

5-1.   Summary of Generic Types of Water Treatment
       Processes  Capable of Meeting Water Quality
       Criteria  	      80

5-2.   Capability of Water Treatment Processes to
       Meet Requirements	      91
                                 ix

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                      ACKNOWLEDGMENTS

              Sincere appreciation is acknowledged for the guidance
and assistance provided by Dennis Cannon,  the present EPA Project
Officer,  and by Alden Christiansen and Guy R. Nelson, the prior
Project Officers of this study program.
              The authors are especially grateful to the late
Lawrence J. Bornstein, who was the Project Manager for The
Aerospace Corporation during most of this program.  His tireless
efforts in producing most of the survey data and evaluations and the
major portion of this report contributed greatly to the accomplishment
of this study.

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                          CONCLUSIONS

              The following conclusions were made as a result of
an Aerospace Corporation study to determine the treatments and costs
applicable to the reuse of liquor from nonregenerable flue  gas desul-
furization systems if there should be a necessity for a system purge
to provide the capacity for the required fresh make-up water. (It should
be noted that the determination of whether scrubbers should be purged
was not made and was not an objective of this study.)  These conclu-
sions are based on the analysis and assessment of four different
scrubber liquors, which were characterized in this study and which are
believed to be representative of most but not all scrubber  liquors.
With these  data as background and using existing criteria and guide-
lines,  some postulated criteria,  and an estimation of purge flow rates,
the following conclusions are made regarding the potential reuse of
purged scrubber liquors:
         a.    Purged  scrubber liquor must be treated if it is
              to be  reused  as power plant service water or if
              it is to be discharged.
         b.    Treatment for service water usage in most cases
              can be accomplished by chemical precipitation
              (e.g., lime-soda  softening, filtration, and  pH
              control when necessary).  This includes usages
              such as scrubber make-up, cooling tower make-
              up, and plant housekeeping.  For an expected mi-
              nority of  cases, excessive chloride content will
              require additional treatment such as reverse
              osmosis.

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            For discharge to surface waters, treatment
            •would consist of a pretreatment and an additional
            treatment (e.g., lime-soda softening, filtration,
            and pH control plus reverse osmosis).  This
            would result in costs approximately twice the
            cost of treatment for service water in most cases.

            Quantities of scrubber liquor in a 1000 Mw
            equivalent unit presumed for treatment for
            purposes of this study are 100 to 300  gpm
            nominally and 700 gpm maximum.  Total treat-
            ment costs (capital and operating), based on a
            30-year equipment life and 18 percent annual-
            ized capital charges,  are as follows:
Flow rate of
liquor to be
   treated

  200 gpm
Lime-soda softening
   and filtration

  $5.00/1000 gal
        or
  0. 05 mill/kWh
Lime-soda softening
   and filtration
 pretreatment plus
 reverse osmosis

  $9.00/1000 gal
         or
  0. 11 mill/kWh
  700 gpm
  $2.50/1000 gal
        or
  0. 09 mill/kWh
  $5.00/1000 gal
        or
  0.22 mill/kWh
To convert:
•   gpm to cu m/hr, multiply by 0. 227.
•   dollar/1000 gal to dollar/cu m, multiply by 0. 264.

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                       RECOMMENDATIONS


              Analyses determined in this study of waste stream
liquors and a review of related data given in Refs. 1 through 3 show
that most lime and limestone scrubber liquors,  including those
produced during steady-state operating conditions, must be treated
if they are to be reused after a scrubber system blowdown.  If it is
shown that a blowdown is required,  it is recommended that the purged
liquor be treated for reuse as power plant service water.
              The potential liquor treatment requirements that were
determined in this study were based on the chemical characterization
of liquors from a limited number of power plants and postulated
purge conditions.  Therefore, it is recommended that additional
studies be made to broaden the data base.  These should include the
characterization of liquors from additional power plant scrubbing
systems, development of more comprehensive usage criteria, de-
tailed analyses of potential purge conditions,  and treatment demon-
strations for those purge conditions, if any,  that are shown to be
necessary.  Specific recommendations are as follows:
         a.    Analyses
              1.    An expanded data base regarding  scrubber
                    liquor chemical characterization  should be
                    determined or assembled.  Any additional
                    factors which were not part of this  study,
                    such as radioactivity, should be considered
                    in this characterization.

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      2.    Detailed analyses should be conducted on
            conditions that may require scrubber purge,
            including purge flow rates and purge cycles.
            These results should be confirmed by oper-
            ational tests.

      3.    Investigations should be made of the tech-
            niques available that may prevent  scrubber
            purge conditions from arising.  These tech-
            niques should be tested on operational
            systems.

      4.    If scrubber purge conditions are determined
            to be unavoidable,  the net effect of waste
            disposal should be determined,  including the
            brine produced  in water treatment systems.

b.    Usage Criteria

      1.    Criteria should be established,  consistent
            with results of the analyses recommended
            above, to define power plant service
            water quality.

      2.    Power plant effluent guidelines and standards
            should be expanded,  consistent with the
            analyses recommended above, to relate  to
            the potential discharge of treated liquors.
c.    Demonstration

      If it is shown that scrubber purge is unavoidable,
      a demonstration of  purged liquor treatment is
      recommended.  At  this time, the  following five
      treatment processes are recommended for con-
      sideration in the selection of hardware for
      demonstration:

      1.     Chemical precipitation (e. g. ,  lime-soda
            softening)

      2.     Chemical precipitation plus reverse  osmosis

      3.     Chemical precipitation plus ion exchange

      4.     Multistage flash evaporation

      5.     Brine concentration

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                             SECTION  1
                          INTRODUCTION

1. 1           INTRODUCTION
              The installation of nonregenerable flue gas
desulfurization systems in coal-burning power plants using lime or
limestone as the  scrubber absorbent requires large quantities of
water (Refs. 1 and 2).  This water circulates through the scrubber
loop as  an alkaline slurry.  The  sulfur waste products that form are
bled from the scrubber, and, in  most systems where a settling tank
or clarifier is used, the supernatant liquor is recirculated to the
scrubber.  Wastes produced by these systems are generally  removed
by disposing of the clarifier underflow,  a filter cake, or a centri-
fuge cake.   They are typically ponded or placed in a landfill after
possible intermediate treatment  for environmental protection.  All
supernate liquors resulting from the waste disposal processes are
returned to  the scrubber loop; hence, the current scrubber systems
can be described as closed-loop  operations.  The only water lost is
that which is evaporated with flue gases or occluded with the solid
waste products.  Fresh water is added to make up for these losses
and is adequate to prevent the formation of scale that results from
precipitation of solids at critical points  within the system.
              This study evaluates the potential reuse of scrubber
liquor within water systems of the power plant, in the event that a
purge is required to maintain adequate capacity for fresh make-up

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water to the scrubber.  The power plant water systems to be evaluated
are those that may accept nonpotable water.  These include cooling towers,
housekeeping service, and scrubber make-up.  Alternatively, these
waters  can be treated for discharge.   In addition, those conditions
that exist or may develop in the operation of flue gas scrubbing
systems that may require a  system purge are postulated.   These
conditions include variable  sulfur content of the coal, variable boiler
load factor,  and  sulfite sludge oxidation.   In an evaluation of the reuse
of scrubber liquor  in other water  systems, it is necessary to deter-
mine the relationship of the water quality of these liquors to the limit-
ing requirements of the intended applications.
              Currently, The Aerospace Corporation is conducting
a study, "Disposal of By-Products From Nonregenerable  Flue Gas
Desulfurization Systems," under Environmental Protection Agency
(EPA) Contract Number 68-02-1010 (Refs.  2 and 3). Data obtained
in that study have shown that scrubber liquors are unacceptable  for
direct discharge  and may not be acceptable for most other water
systems within the power plant without prior water  treatment.
              This program was  initiated because of the potential
unacceptability of direct discharge of  scrubber liquors and the need to
determine the potential reuse of purged liquors as power plant service
water.  Secondary  reasons are the national goal of zero discharge by
1985 in  accordance with the  Federal Water Pollution Control Act
Amendments of 1972, and the requirements for the  1977 and 1983
discharge limitations based on the best practical control technology
available and the best available technology economically achievable
(Ref.  4).  Program objectives and the study approach to characterize
the problem and assess the  technology applicable  for water reuse are
given in Sections 1.2 and  1.3,  respectively.

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1.2           PROGRAM OBJECTIVES

              The principal objectives of this study were to determine

the requirement, if any, for treatment of nonregenerable  flue  gas

desulfurization waters for  reuse and to determine the water treatment
processes and costs applicable for reuse of these waters.

1.3           STUDY APPROACH

              The study objectives were accomplished by performance

of the following  specific tasks:

         a.    Determination of the characteristics of scrubber
              system liquors from four coal-burning power
              plants at the potential discharge points and
              quantification of the constituents affecting water
              quality.
         b.    Identification of the scrubber systems with flow
              diagrams and corresponding liquor flow rates
              under varying scrubber operating conditions
              and estimation where possible of those conditions
              that may require system liquor blowdown.

         c.    Assessment of the quality of liquor waste waters
              against appropriate water quality criteria.
         d.    Survey of water treatment processes available
              and in development and assessment of the
              applicability of those processes deemed capable
              of reducing the concentration of constituents
              of concern in the waste waters to allow reuse
              within the power plant  or to allow direct
              discharge.
         e.    Recommendation of appropriate water treatment
              processes based upon technical and economic
              considerations.

              Samples of  flue gas desulfurization scrubber system

liquors were obtained from four different scrubber systems

(Table 1-1) using lime  or limestone as the  sulfur dioxide absorbents.

The concentration of the trace elements and major  species in the
liquors of the potential discharge flow streams were determined by

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 conventional analytical techniques,  and the results of these analyses
 were assessed against water quality criteria for the nonpotable reuse
 of the water within the power plant operations or for its discharge
 to surface waters.
               Flow-diagrams and rates were determined for the
 flow streams  of the four scrubber systems.  An extrapolation was
 made of the flow rates from each of these systems to an identical
 system of 1000 MW equivalent capacity.
              A technical and economic review was conducted of the
 literature and industry to identify potentially acceptable water treat-
 ment processes.  The economic assessment included initial invest-
 ment, annual  capital charges, and operating expenses for these
 processes.
 1.4           ORGANIZATION OF  THIS REPORT
              Following this introduction, a summary of the total
 study is given in Section 2.  Appropriate figures and tables are
 included to support the findings.
              The technical discussion is given in Sections 3, 4,
 and 5.  Significant features of each of these are as follows:
              Section 3 discusses the water quality criteria selected
 for water reuse in the power plant as nonpotable service water or
 for discharge  to  surface waters.
              Section 4 contains  the flow diagrams, flow rates in
the potential discharge flow  streams, and water balances for the
four scrubber systems.  These data were extrapolated to power plant
 scrubbing systems using the same design and operating characteris-
tics, but operating at 1000 MW capacity equivalent.  This section also
contains complete tabulated data and an assessment of the chemical
characteristics of the scrubber liquors.  An  assessment is  also made
of the concentration of constituents at the potential discharge points
                                 8

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Table  1-1.  POWER PLANT SCRUBBERS SAMPLED




Description of
. scrubber and coal
Scrubber
Type



Equivalent capacity,
MW

Manufacturer


Absorbent

Coal
Source
Sulfur content,
percent
Power plant


Tennessee Valley Authority
(TVA) Shawnee Steam Plant,
Paducah, Kentucky

Venturi and
spray tower


10
(EPA/ TVA
prototype)
Chemical
Construction
Corporation
Lime


Eastern
3.4 (avg)


Turbulent
contact
absorber (TCA)

10
(EPA/TVA
prototype)
Universal Oil
Products
Company
Limestone


Eastern
3.4 (avg)

Arizona Public
Service Company
Cholla Station,
Joseph City,
Arizona

Flooded disk
scrubber (FDS)
and absorption
tower
120
(full-scale)

Research
Cottrell, Inc.

Limestone
and flyash

Western
0.5

Duquesne
Light Company
Phillips Station,
South Heights,
Pennsylvania

Single- and
dual- stage
venturi

125 each
(four full-
scale units)
Chemical
Construction
Corporation
Lime


Eastern
2


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against water quality criteria for reuse as service water in other
water systems in the power plant,  and  discharge to lakes and streams
if the need should arise.
              Section 5 summarizes the  applicable water treatment
processes and equipment described in the literature or in data
available  from industrial contractors.  A technical assessment is
made of the potentially applicable processes, and engineering cost
estimates are made of the initial investment, annual capital charges,
and operating costs.
              Supporting data in the appendixes include a description
of the analytical techniques used to determine the concentration levels
of the constituents in the scrubber liquors, an evaluation of the accu-
racy and precision of the analyses, and the background data used in
preparing the water treatment cost estimates.
                                 10

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                           SECTION 2
                            SUMMARY

2.1           WATER CRITERIA
              In the nonregenerable flue gas desulfurization scrubber
operation,  the scrubbing systems water is continuously recycled
through a closed-loop system.  Normally, there is no discharge of
water from these systems except for the moisture discharged with the
sludge and  that which evaporates from the scrubber.  Under off-
design conditions or any other condition not generally employed in
scrubbers  at this time (Section 4.2),  a  certain amount of scrubber
liquor may have to be purged and treated prior to its reuse.  This
assessment is based on a review of the chemical analyses of system
liquors sampled from four different scrubbing systems (Section 2.3)
and a comparison of these data with selected water use criteria.
              The four systems  from which liquors were analyzed do
not necessarily represent a typical cross section of scrubbers installed
or planned in the U.S.  However, on the basis of other studies (Refs.
1 through 3), it appears that most system liquors will have charac-
teristics within the ranges of those analyzed in this  study.  Some ex-
ceptions, such as the Mohave Station scrubber in Nevada and the
General Motors scrubber in Parma, Ohio (both of which have high
                                 11

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 concentrations of chloride), would require more extensive water
 treatment than the four stations represented in this  study.  The vari-
 ations in scrubber liquor characteristics on a national overview basis
 should be the subject of a separate study; however,  the conclusions
 reached in this report  pertain to only those stations studied, which are
 believed  to be representative of most nonregenerable scrubbing systems
 now operating or to be installed.
               The potential reuse considered for treated scrubber
 liquors are power plant service water,  scrubber reuse, and direct
 discharge to lakes and streams.  Reuse as power plant service water
 or scrubber make-up was considered as a single category,  and direct
 discharge as another.  No specific criteria were found for power plant
 service water usage; therefore, the criteria postulated for  this study
 was based on an informal survey of water requirements now practiced
 within the power industry.  These criteria, listed in Table  2-1 as
 "nonpotable  service  water criteria" were used also  for scrubber make-
 up on the basis of results obtained in  The Aerospace Corporation study
 of scrubber waste disposal requirements (Ref. 3).  For direct dis-
 charge,  several criteria were available,  e.g. , the U.S. Public Health
 Service drinking water standards of 1962 (Ref. 5), federal and state
 water quality criteria documents (Refs.  6 and 7),  EPA proposed cri-
teria for public water supply intake dated October 1973 (Ref. 8), and
the EPA effluent guidelines (Ref. 9).   Of the public service  and drinking
water criteria available,  the EPA proposed critera of October  1973 was
selected as being the most appropriate for this assessment  and is given
in Table  2-1.  The EPA effluent guidelines at this  time  are  not broad
enough to cover most of the major constituents of scrubber  liquors, and
therefore were not listed.  They were used, however,  in a comparative
sense (Section 2.3).
              An examination of Table 2-1 shows that  the criteria
for nonpotable service usage is  much less stringent than the public
service water criteria.   Service water usage is concerned mostly
                                  12

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Table 2- 1.  WATER QUALITY CRITERIA AND RANGE OF
           CONCENTRATION OF CONSTITUENTS IN
           SCRUBBER LIQUORS STUDIED






Constituents
Aluminum
Antimony
Arsenic
Beryllium
Boron
Cadmium
Calcium
Chromium (total)
Cobalt
Copper
Iron
Load
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silicon
Silver
Sodium
Tin
Vanadium
Zinc
Carbonate
Chloride
Fluoride
Sulfite
Sulfate
Phosphate
Nitrogen (total)
Chemical oxygen demand
Total dissolved solids
Total alkalinity (as CaCOj)
Conductance mho/cm
Turbidity, Jackson units
Pi
•Concentration, mg/f (unless otherwise indicated)

Range of
constituent
concentrations
at potential
discharge pointsa
0.03 - 0.3
0.09 - 2.3
<0.004 - 0.3
<0.002 - 0.14
8.0 - 46.
0.004 - 0.11
520. - 3000.
0.01 - 0.5
0.10 - 0.7
<0.002 - 0.2
0.02 - 8.1
0.01 - 0.4
3.0 - 2750.
0.09 - 2.5
0.0004 - 0.07
0.91 - 6.3
0.05 - 1.5
5.9 - 32.
<0.001 . 2.2
0.2 . 3.3
0.005 - 0.6
14.0 - 2400.
3.1 - 3.5
<0.001 - 0.67
0.01 - 0.35

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with nonscaling and noncorrosive properties, whereas the public
service water criteria are concerned with health factors.  Also,
the demand for nonpotable service water in a power plant is always
high, and the water treatment requirements for public service water
usage are more extensive and expensive than that required for
service water (Section 5.3).  Throughout this report assessments are
made for both types of uses.  However, it is assumed that the
treatment of scrubber liquors for reuse as public service water
(i.e. , drinking) would be employed only in rare cases.  Therefore,
the major emphasis in this study is placed on treatment of scrubber
effluent for reuse as service water.
2.2          POWER PLANT SCRUBBING PROCESSES
              As part of this study,  a four-step analysis was made
of the scrubbing process at each of the four scrubbers  (Table  1-1).
This analysis included:
         a.   Examining the operating conditions occurring at
              the time the scrubber liquor samples were taken
         b.   Identifying the water flow rates in the various
              flow streams  of that scrubber system
         c.   Projecting those flow rates to a scrubber  of a
              size equivalent to that required for a 1000 MW
              power plant
         d.   Estimating potential purge rates for  purposes  of
              this study.
              Liquor samples were taken from the four  scrubber
systems of the coal-burning  power plants identified in Table 1-1.
These scrubbers ranged in equivalent capacity of 10 to 400 MW.  The
plants burned either eastern or western coals, and  the flue gases
were scrubbed with  a lime or limestone slurry water that reacted
with the  sulfur dioxide.  The process  flow diagram  for the EPA/TVA
venturi and spray tower scrubber, which is designed for a 10  MW
                                 14

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equivalent capacity, using lime as the absorent, is shown in
Figures  2-1 and 2-2 as an example case.  The water balance for this
system is shown in Figure 2-3 (Ref.  10).  Folio-wing the scrubber is
a clarifier and a vacuum filter.  The separated liquor is recycled
within the scrubbing system.  At the times of sampling, an average
of 3.4 percent sulfur coal was burned, 78 to 93 percent removal of
the sulfur dioxide  was obtained, and 306 cu m/hr (1350 gpm) of water
was recycled into  the scrubber.
               The flow diagram illustrates the amount of water flow-
ing in each major  flow  stream and its percentage as  related to the
total feed water to the scrubber.  In this system, less than 1 percent
of the feed water to the scrubber was lost with the sludge to the dis-
posal pond and to the stack with the  flue gases.  Fresh water was
introduced into the system with the lime slurry mix and by direct
addition  of fresh make-up water into the hold tank.  The extrapolated
values are shown in Figure 2-4 for a water balance for a  1000 MW
scrubber system based on the same process used in the venturi and
spray tower system.  The water flow rates were  scaled up from the
test conditions that existed during sampling at the EPA/TVA facility.
The calculations were based upon operating at 90 percent sulfur
dioxide removal efficiency, using the identical scrubber design, having
the same conditions in the scrubber and burning the same coal, and
retaining the same scrubber liquid-to-flue gas ratio.  For the 1000 MW
capacity scrubber plant, it was estimated that 320 cu m/hr (1410 gpm)
of water would be  lost,  of which 204 cu m/hr (900 gpm)  would escape
from the stack with the flue gases and 115 cu m/hr (510 gpm) would
be occluded with the solids in the filter cake that was sent to the
sludge pond for disposal.   The rates of occluded water in the dis-
charge of all four  scrubbers were used to estimate potential  purge
rates (Section 2.4).
                                15

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  VENTURI
  SCRUBBER
                  See Figure
                     2-2
                  for details)
                                        CLARIFIER
                                        ^
                                  DISCHARGE
           TEST CONDITIONS
           • LIQUID-TO-GAS RATIO: 54.0 gal/1000 CU ft
           • SCRUBBER EFFLUENT SOLIDS: 8 PERCENT
           • CLARIFIER UNDERFLOW SOLIDS: 18 PERCENT
           • FILTER CAKE SOLIDS:  45 PERCENT
           • COAL: 3.4 PERCENT SULFUR
Figure  2-1.
EPA/TVA Shawnee Steam Plant typical flow diagram
for venturi and spray tower scrubber  system:
8.34 MW equivalent operation
                                 16

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                          FLUE
                           GAS
                         OUTLET
            CHEVRON -.
            DEMISTER  >*
      AFTER-SCRUBBER-
                FLUE
                GAS
                INLET
   INLET
IINLt I  —V.   ,  *
SLURRY  ^
-------
                            7.5 gpm
                             0.55%
                                                STACK
      PERCENTAGE VALUES ARE
      PERCENT OF MAXIMUM
      WATER FLOW INTO SCRUBBER
      WATER FLOW RATE IN GALLONS
      PER MINUTE (gpm),  TO CONVERT
      TO cu m/hr MULTIPLY  BY  0.227
                                            43.4 gpm
                                              3.2T
                                      POND
 TEST CONDITIONS
   LIQUID-TO-GAS RATIO:  54.0 gal/1000 cu ft
   SCRUBBER EFFLUENT SOLIDS:  8 PERCENT
   CLARIFIER UNDERFLOW SOLIDS: 18 PERCENT
   FILTER CAKE SOLIDS:  45 PERCENT
   COAL:  3.4 PERCENT SULFUR
Figure 2-3.
Water balance for EPA/TVA Shawnee Steam Plant
venturi and spray tower scrubber  system:
8.34 MW equivalent operation
                               18

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                             900 <
                              0.5S
                    am
         VENTURI
         AND
         SPRAY
         TOWER
         SCRUBBER
                      163,000 gpm
                         100%
                                                STACK
                                      4800 gpm
                                        !.95T
        PERCENTAGE VALUES ARE
        PERCENT OF MAXIMUM
        WATER FLOW INTO SCRUBBER

        WATER FLOW RATE IN
        GALLONS PER MINUTE (gpm).
        TO CONVERT TO cu m/hr
        MULTIPLY BY 0.227
                                            5200^
                                       POND
  EXTRAPOLATED OPERATING CONDITIONS

  • LIQUID-TO-GAS RATIO: 54.0 gal/1000 cu ft

  • SCRUBBER EFFLUENT SOLIDS: 8 PERCENT
  • CLARIFIER UNDERFLOW SOLIDS:  18 PERCENT

  • FILTER CAKE SOLIDS:  45 PERCENT

  • COAL:  3.4 PERCENT SULFUR

  • SO2 REMOVAL EFFICIENCY:   90 PERCENT
Figure  2-4.
Water balance for venturi and spray tower scrubber
system (extrapolation based on EPA/TVA Shawnee
Steam Plant process):  1000 MW equivalent
                                19

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               Because each process is configured differently and
 has its own individual operating characteristics, the data obtained  for
 these four scrubbers cannot be extrapolated directly to other systems.

 2.3           SCRUBBER LIQUOR CHARACTERIZATION AND
               ASSESSMENT
               Table 2-1 lists the constituent concentrations found  in
 the scrubber liquor samples taken from the potential discharge points
 of the four scrubbers.
               Variations in the concentration of the constituents are
 due in part to the different operating conditions  that existed among
 plants.  For example, the Arizona Public Service Cholla Station
 operates in a tightly closed scrubber loop situation resulting  in high
 concentrations of chlorides and total dissolved solids in the bleed
 stream from the flooded  disk scrubber slurry tank that is presently
 the discharge point for this system (Ref.10).  Conversely, the
 Duquesne-Phillips Station system has experienced operating conditions
 requiring high water use within the scrubbing  system which diluted
 the concentration of the dissolved ingredients  (Ref.  11).  Variations
 in scrubber liquor composition at the potential discharge points were
 also caused by differences in the coal composition, in the absorbents,
 and in the scrubber  process design and operating characteristics.
               For the scrubber liquor to be reused in other systems
 within the power plant, it will be necessary to reduce the concentra-
 tion of boron, magnesium, calcium, or sulfate, from one or more
 of the scrubber flow streams studied.  An adjustment of the pH of the
 water would  also be necessary for some of the flow streams.  These
 reductions and adjustments of the characteristics of purged liquor
would make the liquor applicable for reuse within the scrubber also.
               The concentration of lead, mercury,  selenium,
 chlorides,  and sulfates and the pH in the scrubber liquor streams
                                 20

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from all four power plants exceed the EPA-proposed criteria for
public water supplies.  In addition,  in one or more of the  streams
the concentration of arsenic,  boron, cadmium, chromium (total),
iron, manganese, and silver  also exceed the criteria,  but not
simultaneously.  Because these ingredients  exceed the criteria, the
scrubber liquor must be treated before it can be discharged.
               The EPA effluent guidelines and standards  (Ref. 9),
though not as restrictive or as encompassing as public water supply
criteria,  require treatment of some of these liquors because of limi-
tations on iron and pH level.  However, this approach for direct
discharge should be used with caution since  the major constituents
of the liquor are not specified.
               The following section summarizes treatment tech-
nologies available for these purposes and discusses the relative com-
plexities  of treatment for reuse as  service water and discharge to
surface waters.
2.4            WATER TREATMENT TECHNOLOGY
               AND COSTS
               A review was made of the literature,  and technical
meetings and discussions were held with water treatment processors
and equipment manufacturers to determine the water treatment tech-
niques applicable to the potential reuse or discharge of scrubber
liquor.  The results of this review  are summarized in Table 2-2,
which identifies the generic types of water treatment processes,  the
development status of each,  and indicates whether or not  the water
would meet the water quality criteria.
               It was found that a treatment process such as lime-
soda softening  which reduces the concentration of all constituents,
except soluble  sodium and chloride salts, would be sufficiently effec-
tive that the water of the four liquors studied would be acceptable
                                 21

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Table 2-2.  SUMMARY OF GENERIC TYPES OF WATER
           TREATMENT PROCESSES CAPABLE OF
           MEETING WATER QUALITY CRITERIA
Water treatment
process
Complete system
Multistage evaporation
Tower distillation
Brine concentration
Spray drying
Vacuum freezing
Solar distillation
Rotating bipolar electrodes
Partial operation
Filtration or centrifugation
Ultrafiltration
Reverse osmosis
Ion exchange
Chemical precipitation
(including lime -soda
softening)
Electrodialysis
Selective absorbent
Electrochemical; fluidized
bed
Foam separation
EPA-proposed
public water
supply intake,
October 1973

Yes
Yes
Yes ,
Yes
Yes
Yes
No

No
No
Yes
Yes
No
Yes
No
No
No
Nonpotable
service
water

Yes
Yes
Yes
Yes
Yes
Yes
No

No
No
Yes
Yes
Yes
Yes
No
No
No
Status

Operational
Operational
Operational
Operational
Development
Development
Laboratory

Operational
Operational
Operational
Operational
Operational
Development
Laboratory
Laboratory
Laboratory
Used with other operations to form a total water treatment system
                        22

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(after pH adjustment, if necessary) for use as power plant service
water (e.g.,  cooling tower makeup,  heat exchangers,  scrubber
makeup, and housekeeping).  In plants -where a chloride concentration
greater than 5000 mg/i is unacceptable, lime-soda  softening would
have to be followed by an additional process (e.g. , reverse osmosis).
This value was selected on the basis of an informal  survey of the
industry.  Variations can be expected  depending on the characteris-
tics of any particular plant.
              The use of scrubber liquor in a public water supply
would require a complete treatment,  e.g.,  lime-soda softening
followed by reverse osmosis in all cases  and, in some cases,  pH
adjustment.  Therefore, treating the liquor for  reuse as drinking
water can require a treatment process and cost appreciably in excess
of that required for reuse as service water.
              Other existing treatment processes such as multistage
flash evaporation, brine concentration, and softening-ion exchange
could be used instead of  softening and reverse osmosis,  but would
generally be less cost effective. Processes in development have not
yet shown that they are cost effective.
              A preliminary estimate was made of  the amount of
water that may have to be removed from the scrubber loop to provide
the adequate volume for fresh water make-up requirements
(Section 4. 2).  Two scrubber systems were considered:  a venturi and
spray tower  system and a turbulent contact absorber system.  The
greatest amount of excess liquor that may have to be removed for
maintenance of the water balance may occur in the case where gypsum
is formed and the excess liquor is subsequently removed from the
scrubber loop.  The least amount may be in the case of a reduced
load factor on the system.  The quantity of water to be removed from
a 1000 MW equivalent system appears to be in the range of 22.7 to
68. 1 cu m/hr (100 to 300 gpm) but can possibly be as  high as
                                23

-------
160 cu m/hr (700 gpm).  A detailed analysis of potential scrubber
purge flow rates was not a subject of this study; however,  an estimate
was considered necessary because of the wide variations in treatment
costs as a function of treatment system size. For this reason, costs
were determined and plotted for flow rates up to 1000 gpm. Specific
case values are presented for the lower nominal and  the upper end
of the estimated flow rate range, i.e. ,  200 and  700 gpm.
              The total cost, including capital charges and operating
expenses, for treating 45.4 and 160  cu m/hr (200 and 700  gpm) of
scrubber liquor using a lime-soda process varies from 0.  51 to
0.25 cents per gallon.  This converts to a reverse order of approxi-
mately 0.05 to 0.09 mills per kWh at an average annual production
of 4560 million kWh over  30 years.  Likewise, when  lime-soda pre-
treatment is combined with reverse  osmosis, these values are
approximately double, i.e.,  0. 9  to 0. 5 cents per gallon and 0. 1 to
0.2 mills per  kWh, respectively. These  costs are shown  on
Figures  2-5 and 2-6 where values are given for flow  rates from 200
to 1000 gpm.
                                24

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              • 1974 DOLLARS
              • 1000 MW POWER PLANT SCRUBBER
              • COSTS BASED ON 30-YEAR ANNUALIZED COSTS, 4560 OPERATING
               HOURS PER YEAR, AND CAPITAL CHARGES OF 18%
              • LAND COSTS NOT INCLUDED
"8   2.0
                WATER TREATMENT COST, CENTS PER GAL TREATED
                  n in    nil    o 20    0 25    0.30   0.35    0.40
                                                            0.45
                                                                   0.50
O
t;
I
                                 I
    1.5  -
    1.0  -
0.5
                                         WATER TREATMENT PLANT
                                         CAPACITY, gpm
             0.025     0.050    0.075    0.100
                  WATER TREATMENT COST.  MILLS PER KWh PRODUCED
                                                                   200 gpm
         Figure 2-5.   Estimated costs of lime-soda softening
                         and filtration
                                       25

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                 • 1974 DOLLARS

                 • 1000 MW POWER PLANT SCRUBBER

                 • COSTS BASED ON 30-YEAR ANNUALIZED COSTS. 4560 OPERATING
                   HOURS PER YEAR, AND CAPITAL CHARGES OF 18%

                 • LAND COSTS NOT INCLUDED
8
•D


|

IO
g
3
j
2

S  2.0
          0.10
                  WATER TREATMENT COST,  CENTS PER GAL TREATED

                 0.20    0.30    0.40   0.50    0.60    0.70   0.80
                                                             0.90
   3.0
UJ


i/i
tu
1.0
         'TO I
       CONVERT
         FROM
                                I
                                    I
                             I
      I
I
              TO
                     MULTIPLY
                       BY
     gpm

     gal
cu m/hr

liter
              I
WATER TREATMENT
PLANT CAPACITY, gpm
                                                       1.00
            0.05      0.10     0.15     0.20     0.25      0.30     0.35

                 WATER TREATMENT COST, MILLS PER kWh PRODUCED
                                                                    0.40
     Figure  2-6.  Estimated costs  of lime-soda and filtration
                    pretreatment plus reverse  osmosis
                                    26

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                            SECTION 3
                    WATER QUALITY CRITERIA

              The scrubber liquor is continuously recycled in the
flue gas desulfurization scrubbing system.  Currently, a bleed stream
of scrubber slurry is withdrawn from the scrubber loop and is
dewatered; the resultant solids are sent to  a waste disposal pond.
The supernate liquid (system liquors) and make-up water,  which is
added to replace  the water lost  with the waste product and by evapora-
tion with the  flue gases, are returned to the scrubber.  If the  scrubber
liquors  are to  be reused within the power plant or discharged, they
must meet the accepted water quality criteria for their intended use.
              Large quantities of water are needed in the power
plant operations for nonpotable  uses (e.g., cooling water,  scrubber
make-up, housekeeping, and irrigation of the  power  plant vegetation).
These uses can be divided into nonpotable water for use throughout
the plant that will not cause scaling or corrosion of the equipment
and irrigation water.  After the identification of the specific water
use, it is necessary to establish criteria to ensure that the water
will be of sufficient quality for that use.
              The October 1973 EPA-proposed criteria for public
water supply intake (Ref. 8) is part of the data base for the 1985 goal
of zero  discharge of pollution into the nation's waters as defined by
Public Law 92-500.  These criteria were used to judge the quality of
the scrubber liquor that might be discharged.  A comparison  of the
                                 27

-------
 EPA criteria with the U.S. Public Health Service (USPHS) 1962
 criteria (Ref. 5) shows a similarity except that the USPHS criteria
 have more stringent limitations on the concentration of total dissolved
 solids (TDS) (500 mg/j? versus no limit) and arsenic (0.05 versus
 0. 10 mg/i).  Conversely, the EPA criterion is tighter on the con-
 centration of nitrates (10 versus 45 mg/jf).
              The service water and  discharge water criteria are
 shown in Table 2-1.  Because there are no published or approved
power plant service water criteria, the service water values used
were based upon the literature and discussing requirements with
water treatment processors and power plant operating personnel.
 These values are goals assumed acceptable for service water use
within most power plants;  they are not absolute requirements.  A
specific power plant may have special requirements depending upon
its operation and local restrictions.   The EPA-proposed criteria
for public water supply were used as the discharge  criteria.
                                28

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4.1
               SECTION 4
SCRUBBER LIQUOR CHARACTERIZATION

  POWER PLANT SCRUBBER LIQUOR SAMPLING
              The data base for this study was prepared from samples
taken from the four scrubbers listed in Table 4-1.

             Table 4 -1.  POWER PLANTS SAMPLED
Power plant
TVA Shawnee
Steam Plant
TVA Shawnee
Steam Plant
Arizona Public Service
Company Cholla
Station
Duquesne Light
Company Phillips
Station
Scrubber
systems
Venturi and
spray tower
Turbulent con-
tact absorber
Flooded disk and
absorption tower
Single- and dual-
stage venturi
Coal
Eastern

Eastern

Western
Eastern
Absorbent
Lime

Limestone

Limestone and
fly ash
Lime
4.2
  POTENTIAL SCRUBBER PURGE CONDITIONS
              Power plant scrubbing systems are fundamentally iden-
tical although each installation is unique in detail design features.
Each scrubber vendor has developed hardware having basic system
design differences; cither differences also exist as a consequence of
                                 29

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coal type,  fly ash collection facilities, and scrubber size.  The
similarities among scrubbing facilities are based primarily on the
chemistry of scrubbing.  For the lime or limestone systems, an
alkaline slurry is recirculated between the scrubber and a reaction
tank where the effluent from the scrubber reacts with the absorbent
material.  A bleed stream from the reaction tank carries off solid
reaction products (and fly ash) and passes through a primary and often
secondary dewatering system.  A supernate liquor is returned to the
system and, although clear, it is saturated with dissolved calcium
sulfite and/or calcium sulfate salts.
               Under normal conditions, no system bleed has been
found necessary.  Normal operating conditions are here considered as
those conditions defined by design criteria and include characteristics
of the boiler, coal, fly ash,  existing hardware for retrofit systems,
absorbent,  disposal facilities,  and any other consideration peculiar to
that facility or design.  The only water loss from these systems occurs
by evaporation in the stack and from water lost to the disposal site by
occlusion with the solids.  In the operation of scrubber systems studied
for this report and other systems now known to be operating, no system
bleed is considered necessary for continuous operation.   The fresh
water used by the pump seals and demister spray provides enough
make-up water to equal the loss  of water by evaporation and solids
disposal.   The solids disposal includes  enough dissolved solids in its
occluded water to normally meet the bleed requirements necessary
to limit dissolved solids build-up.
              Several circumstances not now considered normal
operating conditions may exist in the future that could affect the water
balance of the system and create a need for a system purge.  One such
circumstance can arise when a scrubber is operated at a flue gas mass
load level below some critical value created by low boiler loading, or
alternatively under circumstances whereby lower sulfur coal is used
than that for which the system was designed.  Under these circumstances,

                                 30

-------
reduced solid quantities are  formed in the reaction tank and a
reduced bleed stream flow must be established so that a constant
solids content can be maintained in the  recirculation system of the
scrubber.  (The solids content of recirculating liquor is maintained
so as to provide suitable nuclei in the scrubber onto which newly
precipitated material may crystallize).  The reduced bleed decreases
the loss of water from the system.  However,  the need for fresh
make-up water, which is dictated primarily by the requirement  for
demister water for scale prevention, is not reduced.  Thus, when
the fresh water requirement of the system is  satisfied,  an excess in
system water would occur and a system purge would be  required to
maintain proper water balance. Of the power plants sampled in this
study, one has experienced this condition while operating  the scrubber
at 33 percent of design load.
              Another condition that could force a system bleed may
arise under circumstances in which operational changes are made
from that of the system design.  For example, the oxidation of sulfite
sludge to a sulfate sludge may evolve into a normal operating prac-
tice as a consequence of the greater efficiency in dewatering gypsum
sludge and improved disposal practices. Under this circumstance,
more sludge liquor would return to the scrubber because of the
improved separation of liquid from the solids.  The effect would be a
reduction of water loss from the system.  If this reduction reduces
the make-up requirement below the fresh water requirement,  the
condition of excess water would result  as described in the previous
paragraph and a system bleed would be required to maintain water
balance.  This same condition may also exist if any of several im-
proved dewatering methods are used.
               As yet another circumstance, major repairs or hard-
ware replacement are unavoidable,  although not necessarily consid-
ered part of normal operation.  If major maintenance can be
                                31

-------
prescheduled, it is often possible to divert the liquor from one system
to another over  a period of time.  However, major repairs are often
the result of more catastrophic circumstances, and the need for a
quick blowdown  may become an immediate  requirement. Acceptable
plans for such a contingency should be part of every plant's operation,
and the reuse of these waters in other parts of the power plant is
recognized as an alternative to be considered.
              In each of the power plants sampled, reported values
for total water balance are those for  circumstances that are consid-
ered as normal  and typical operating conditions, i.e., conditions
within the range of design  criteria and typical for the operation of
          >'<
that plant.   Normal design criteria include maximum power output
and a level of reduced power output that is  usually undefined and
depends  on the flexibility of the system.  Thus, the point at which
fresh water requirements  exceed make-up  water requirements such
that normal operation  is affected must be determined empirically.
From the power stations sampled,  it can be estimated that this point
is reached in the vicinity of about 50  percent of the maximum design
parameter,  i.e., 50 percent load factor or 50 percent reduction in
sulfur content.  The reduced flue gas mass loading that may accom-
pany startup or  shutdown of either boiler or scrubber causes a tem-
porary excess liquor problem over such a short period of time that
the capacity of a disposal pond is usually more than adequate to
accept this excess water and, under normal conditions, to return it
in the recirculation system.
 In the one case in which the plant was operating at 33 percent of de-
 sign load, a system purge was necessary.  Reported values were.
 corrected for this condition when extrapolating to full scale.
                                 32

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4.2.1         Shawnee Steam Plant Venturi and Spray Tower
              Scrubber System
              This system is one of three parallel scrubber modules
installed on a 150 MW coal-fire boiler at the TVA Shawnee Steam
Plant,  Paducah,  Kentucky (Ref. 10).  These modules were installed to
provide a large,  versatile prototype  system as  a test bed for wet
scrubbing sulfur dioxide (SCO  and particulates  from boiler flue gas.
Each module has a 10 MW equivalent capacity; this is achieved by
taking  approximately 14. 15 cu  m/sec (30,000 acfm) of flue gas from
the ductwork of  Boiler No.  10 upstream of the electrostatic precipi-
tators. This dual-stage scrubber, which is shown in Figure 4-1,
consists of a venturi  with an adjustable plug that permits  control  of
the pressure drop in  the first stage  and a spray tower after-scrubber
in the  second stage.  It was manufactured by the Chemical Con-
struction Corporation (Chemico).
              Flue gas entering the  scrubber passes through  the
venturi and then upward through the spray tower countercurrent to
the scrubbing liquors that are  recirculated from the reaction tank.
The effluent liquors return to the reaction tank where pH is adjusted
with a  slaked lime slurry.  A bleed  stream from the reaction  tank is
routed to a clarifier.  The clarifier overflow is returned to the
reaction tank; the underflow passes  through a vacuum filter; and the
filtrate is returned to the reaction tank.  The filter cake is  discharged
to a disposal pond. A flow diagram is  shown in Figure 4-2.
              On three occasions, slurry samples were taken from
three stations in the  system: (a) the scrubber effluent to the reaction
tank, (b) the clarifier underflow to the  vacuum filter, and (c) the
filtrate from the vacuum filter to the hold tank.  The  scrubber test
conditions are presented in Table 4-2,  and the  analysis of the liquors
from these sample points is  presented  in Table 4-3.  Although the'
                                33

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         CHEVRON -
         DEMISTER
  AFTER-SCRUBBER
            FLUE
            GAS
            INLET
THROAT
ADJUSTABLE X
PLUG
VENTURI
SCRUBBER
                      FLUE
                       GAS
                     OUTLET
INLET  —v.   _JL_
SLURRY  ^
-------
VENTURI
SCRUBBER
                (See Figure
                   4-1
                for details)
                                      CLARIFIER
                                      ^>
                                DISCHARGE
        TEST CONDITIONS
          LIQUID-TO-GAS RATIO: 54.0 gal/1000 cu ft
          SCRUBBER EFFLUENT SOLIDS: 8 PERCENT
          CLARIFIER UNDERFLOW SOLIDS: 18 PERCENT
          FILTER CAKE SOLIDS:  45 PERCENT
          COAL: 3.4 PERCENT SULFUR
          ADDITIONAL CONDITIONS AT TIME OF SAMPLING
           SHOWN IN TABLE 4-2
  Figure 4-2.
Typical flow diagram for EPA/TVA Shawnee
venturi and spray tower scrubber system:
8. 34 MW equivalent operation
                               35

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Table 4-2.  TEST CONDITIONS FOR EPA/TVA SHAWNEE
           VENTURI AND SPRAY TOWER SCRUBBER
Parameters
Gas rate,
cu m/sec
acfm
Equivalent megawatts
SO- input, ppm
SO? removal, percent
pH control
Dust input,
gm/cu m
gr/scf
Scrubber, effluent
solids, percent
Liquid-to-gas ratio,
gal/1000 cu ft
Sample datea
3/19/74

11.8
25,000
8.3
2,600
93
8.0

8.0
3.5
8
54.0
5/17/74

11.8
25,000
8.3
3,280
78
8.0

8.0
3.5
8
54.0
6/27/74

11.8
25,000
8.3
2,700
84
8.0

8.0
3.5
8
54.0
o
Data base used in extrapolation of scrubber system to 1000 MW
equivalent size scrubber and for determining water balance.
Water balance at time of testing is shown in Figure 4-3, and
values extrapolated to 1000 MW equivalent are shown in
Figure 4-14.
                          36

-------
Table 4-3.  ANALYSES OF SCRUBBER LIQUORS FROM EPA/
            TVA SHAWNEE VENTURI AND SPRAY TOWER
            SCRUBBER SYSTEM

Scrubber test conditions at time of sampling shown in Table 4.2.
Concentration in milligrams per liter of filtered liquor  (Whatman 40).
Scrubber
liquor
constituents
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr) (total)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Molybdenum (Mo)
Nickel (Ni)
Potassium (K)
Selenium (Se)
Silicon (Si)
Silver (Ag)
Sodium (Na)
Tin (Sn)
Vanadium (V)
7.inc (/n)
Total carbonate
Chloride (Cl)
Fluoride (F)
SuUite
Sulfate
Phosphate
Total nitrogen
Chemical oxygen demand
Total dissolved solids
Total alkalinity
Conductance, mho/cm
Turbidity, Jackson
units
PH
In-process data
Potential discharge point data
Sample location
Scrubber effluent
Clarifier underflow
Drum vacuum filter filtrate
Sample date
3/19/74
0.22
0.39
0. 15
0.05
--
0.02
980
0.02
..
0.08 '
0.77
0.03
53
..
0. 10
_ _
0.5
8.4
0.08
0.4
0.09
33
-.
..
0.09
<10
1230
<0.3
450
1000
<0. 1
<0.001
220
3500
54
0.006

<3
5.19
5/16/74
0.12
2. 1
0. 15
0.05
--
0.04
2360
0.02
0.6
0.03
0. 14
0.12
220
0.4
<0.05

0.25
21
1.9
1.8
0.01
108
..
..
0.02
<10
4400
1.5
3.0
1500
<0.1
<0.001
--
8700
-•
0.013

<3
5.67
6/27/74
1.54
1.01
0.04

-------
 scrubber effluent is not a potential discharge point, it was included to
 identify the scrubber chemistry.  Analysis of samples taken down-
 stream of the reaction tank has shown that they are essentially equiva-
 lent in all cases  and that they represent the water quality of the liquor
 at any potential discharge point.
               The water balance for this  system is presented in the
 simplified flow diagram in Figure 4-3.  The actual water flow in gal-
 lons per minute is  an integrated average for the equivalent power
 capacity specified on the three days for the nominal coal sulfur con-
 tent of 3.4 percent  and for a 78 to 93 percent efficiency in SO2
 removal from the flue gas.  In each case,  flow rates are given as
 water flow;  slurry  flows are greater because of the incorporation  of
 solids in liquors  in varying amounts at different points in the system.
 The percentages  shown are based on the maximum water flow in the
 system,  which in this  case are  represented by the  recirculation
 liquor from the reaction tank to the  scrubber.
 4.2.2          EPA/TVA Shawnee Turbulent Contact Absorber
               (TCA) Scrubber System
               This system is also one of the three parallel scrubber
 modules installed on Boiler No.  10 at the Shawnee  Steam Plant. This
 module has  the same design capacity as that of the system described
 in Section 4. 2. 1 (Ref. 10).  The  TCA scrubber (manufactured by
Universal Oil Products) uses a fluidized bed of low density plastic
 spheres that are  free to move between retaining grids (Figure 4-4).
 Three stages of grids are used to obtain sufficient  surface for
adequate scrubbing efficiency.
              A  system flow diagram is shown in Figure 4-5.  Flue
gas enters the  scrubber from a side port,  passes upward through the
 grids, contacts the levitated plastic spheres, and exits through
chevron-shaped demisters.   Scrubbing liquor from the reaction tank
                                38

-------
    • PERCENTAGE VALUES ARE
     PERCENT OF MAXIMUM
     WATER FLOW INTO
     SCRUBBER
    • WATER FLOW RATE  IN
     GALLONS PER MINUTE (gpm)
     TO CONVERT TO cu  m/hr
     MULTIPLY BY 0.227
                                       4.2 gpm
                                        0.31%
                                    POND
TEST CONDITIONS
  LIQUID-TO-GAS RATIO:  54.0 gal/1000 cu ft
  SCRUBBER EFFLUENT SOLIDS:  8 PERCENT
  CLARIFIER UNDERFLOW SOLIDS:  18 PERCENT
  FILTER CAKE SOLIDS: 45 PERCENT
  COAL:  3.4 PERCENT SULFUR
  ADDITIONAL CONDITIONS  AT TIME OF
  SAMPLING SHOWN IN TABLE 4-2
    Figure 4-3.
Water balance for EPA/TVA Shawnee
venturi and spray tower scrubber
system: 8. 34 MW equivalent operation
                            39

-------
                         FLUE
                          CAS
                         OUTLET
    CHEVRON DEMISTERS
 INLET KOCH TRAY
 WASH LIQUOR
                                   KOCH TRAY
                STEAM
                SPARGE
        RETAINING GRIDS
<
              FLUE   ,.
              GAS  H>
                   ^^
              INLET
                                         EFFLUENT KOCH
                                         TRAY WASH LIQUOR
                        A  A A
                         o oi,
                         00 o
                         <%>-.*
                                  INLET SLURRY
                                  FROM REACTION
                                  TANK
                                .^•MOBILE PLASTIC
                                *  SPHERES
                             EFFLUENT
                             SLURRY
                        REACTION
                          TANK
Figure 4-4.  Schematic of EPA/TVA TCA scrubber
                           40

-------
                           REHEATER
                                                 STACK
            TCA
          SCRUBBER

          (See  Figure
             4-4
          for  details)
   TEST CONDITIONS
   • LIQUID-TO-GAS RATIO:  54.6 gal/1000 cu ft
   • SCRUBBER EFFLUENT SOLIDS:  8 PERCENT
   • CLARIFIER UNDERFLOW SOLIDS: 40 PERCENT
   • COAL: 3.4 PERCENT SULFUR
   • ADDITIONAL  CONDITIONS AT TIME OF SAMPLING
     SHOWN IN TABLE 4-4
Figure 4-5.   Typical flow diagram for EPA/TVA Shawnee
              TCA scrubber system:  6.8 MW equivalent
              operation
                             41

-------
is sprayed against the rising flow of flue gas, percolates downward
through the scrubbing stages, and exits to the reaction tank.  The pH
is adjusted with a limestone slurry that is also fed to the reaction
tank.  A bleed stream from the reaction tank is passed through a
clarifier.  The overflow returns to the reaction tank, and the under-
flow is pumped to a disposal pond.  No secondary dewatering is done
in this system.
               On two occasions slurry samples were taken from the
scrubber effluent and clarifier underflow.  Only the clarifier under-
flow represents the potential discharge points.  The  test conditions
of the  scrubber on these days are presented in Table 4-4, and the
results of the liquor analysis from these sample points is presented
in Table 4-5.
               The water balance for this system is presented in the
simplified flow diagram in Figure 4-6.  The water flow is given in
gallons per minute, and the percentages are based on maximum flow
to the  scrubber.  The reported flow rates are for the equivalent power
capacity treated as specified, for the nominal coal sulfur content of
3.4 percent,  and for about an 86 percent SO? removal efficiency.
4.2.3          Arizona Public Service Company Cholla Power
               Station -- Flooded Disk  Scrubber (FDS) and
               Packed Absorption Tower Scrubber System
               This system consists of two  parallel dual-stage scrub-
bers installed on a 115 MW coal-fired boiler at the Cholla Station,
Joseph City,  Arizona (Ref.  11).  Each  scrubber is designed for 60
MW equivalent power generation capacity.  The flooded  disk and
absorption tower scrubbers (Figure 4-7), (manufactured by Research
Cottrell, Inc.) were designed to handle fly ash and remove SO- from
the flue gas.   The FDS is a variable throat,  flooded disk,  venturi-
type  scrubber used principally to remove the fly ash entrained in the
                               42

-------
 Table 4-4.  TEST CONDITIONS FOR EPA/TVA
            SHAWNEE TCA SCRUBBER
Parameters
Gas rate,
cu m/sec
acfm
Equivalent megawatts
SO- input, ppm
SO_ removal, percent
pH control
Dust input
gm/cu m
gr/scf
Scrubber effluent solids,
percent
Liquid-to-gas ratio,
gal/1000 cu ft
Sample date
11/27/73

9.7
20,500
6.8
2,700
83
5.9

8.0
3.5
16.0

54.6
6/15/74a

9.7
20,500
6.8
2,400
86
5.5

8.0
3.5
8.0

54.6
Data base used in extrapolation of scrubber system to 1000 MW
equivalent size scrubber and for determining water balance.
Represents stable test conditions.  Water balance at time of
testing is shown in Figure 4-6, and values extrapolated to
1000 MW equivalent are shown in Figure 4-15.
                            43

-------
Table 4-5.  ANALYSES OF SCRUBBER LIQUORS FROM EPA/
            TVA SHAWNEE TCA SCRUBBER SYSTEM
Scrubber test conditions at time of sampling shown in Table 4-4.
Concentration in milligrams  per liter of filtered liquor (Whatman 40).



Scrubber
liquor
constituents
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr) (total)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Molybdenum (Mo)
Nickel (Ni)
Potassium (K)
Selenium (Se)
Silicon (Si)
Silver (Ag)
Sodium (Na)
Tin (Sn)
Vanadium (V)
Zinc (Zn)
Total carbonate
Chloride (Cl)
Fluoride (F)
Sulfite
Sulfate
Phosphate
Total nitrogen
Chemical oxygen demand
Total dissolved solids
Total alkalinity
Conductance, mho/cm
Turbidity, Jackson
units
pH
In -process data
Potential discharge point data
Sample location
Scrubber effluent
Clarifier underflow
Sample date
11/27/73
..
--
0.2
0.01
--
0.04
1800
0.04
_-
0.05
	
0.06
900
--
--
..
0. 16
6.3
0.2
--
--
63
--
--
0.84

3400
2.3
--
2000
<0.1
<0.005
--
12000
--

<3

5.90
6/15/74
2.7
2.0
0.4
0.07
--
0.005
840
0. 16
0. 16
0.02
0.35
0.35
2800
--
<0.5
..
0.44
-.
--
--
0.008
--
--
--
0.03

3300
2.3
1400
9500
<0.1
<0.005
--
17800
--
0.027
<3

4.64
11/27/73
	
--
0.3
0.004
—
0.004
..
0.5
--
--
	
0. 12
600
--
0.05
--
0. 50
5.9
0.2
--
._
--
--
--
0.35
_ _
1900
--
..
--
<0. 1
<0.005
--
11000
150
• _
<3

9.50
6/15/74
0.6
1.4
0. 1
0.05
~ ~
0.004
520
0.09
0. 10
0.01
0.02
0.23
2750
--
<0.05
--
0.33
--
--
--
0.005
--
--
--
0.02
	
2300
6.5
80
10000
<0. 1
<0.005
--
15000
--
0.015
< 3

7.96
                            44

-------
                     fT 15 gpm
                      100%
                                             STACK
                                  28 gpm
                                   2.52
                                        10.1 gpm
                                          .9%
32.6 gpm
  2.9%

 • PERCENTAGE VALUES ARE
   PERCENT OF MAXIMUM
   WATER FLOW INTO SCRUBBER

 • WATER FLOW RATE IN
   GALLONS PER MINUTE (gpm).
   TO CONVERT TO cu m/hr
   MULTIPLY BY 0.227
                                   POND
  TEST CONDITIONS
   LIQUID-TO-GAS RATIO:  54.6 gal/1000 cu ft
   SCRUBBER EFFLUENT SOLIDS:  8 PERCENT
   CLARIFIER UNDERFLOW SOLIDS:  40 PERCENT
   COAL:  3.4 PERCENT SULFUR
   ADDITIONAL CONDITIONS AT  TIME OF
   SAMPLING SHOWN IN TABLE  4-4
  Figure 4-6.
Water balance for EPA/TVA Shawnee
TCA scrubber system:  6.8 MW
equivalent operation
                          45

-------
                                              REHEATER
                                           EXIT GAS
                                           TO STACK
     SECONDARY MIST
     ELIMINATOR

     PRIMARY MIST
     ELIMINATOR
         FLUE GAS
          INLET
FLOODED1
  DISK
SCRUBBER
  (FDS)
                            'ABSORBER'
                             PACKING
               PACKED
              ABSORPTION
                TOWER
                             CYCLONIC
                             DEMISTER
                                 DEMISTER
                                 SPRAY WATER
                                                    FROM
                                                    ABSORPTION
                                                    TOWER FEED
                                                    TANK
TO ASH
DISPOSAL
POND
                     FDS
                 SLURRY TANK
                                             TO ABSORPTION
                                             TOWER FEED
                                             TANK
 Figure 4-7.
Schematic of Arizona Cholla Station FDS and
packed absorption tower scrubber
                              46

-------
flue gas after passing through the upstream mechanical collectors
that remove 80 percent of the fly ash.
              A flow diagram is shown in Figure 4-8.  A forced draft
booster fan forces flue gas into the FDS and then into the base of the
absorption tower.  Recirculating limestone  slurry is pumped from the
FDS slurry tank into the FDS scrubber tangentially above the throat
and at the disk.  The  scrubber slurry is carried with the flue gas
through the cyclonic demister and then returns to the FDS slurry
tank after having removed the fly ash and 15 to 30 percent of the SO-.
The flue gas  rises through the packed absorption tower countercurrent
to limestone  slurry recirculated from the absorption tower feed tank.
Of the two  parallel absorption towers, one is operated as a packed
tower and the other as a spray tower.  The  slurry returns to the
absorption tower feed tank after scrubbing approximately 40 to  60
percent of  the remaining SO- from the flue gas.  Adjustment of pH is
made by the addition of a limestone slurry to the absorption tower
feed tank.  A crossfeed between the absorption tower feed tank  to the
FDS slurry tank provides a bleed for the absorption tower scrubbing
liquors  and a supply of absorbent for the FDS liquors.  The scrubber
system bleed is made from the FDS slurry tank and is used without
dewatering to slough the mechanically collected fly ash to  a disposal
pond.
              On two occasions, slurry samples were taken from the
FDS slurry tank and the absorption tower feed tank.  Only the output
of the FDS slurry tank can be considered a potential water discharge
point. The operating conditions existing in the scrubber at the  time
of sampling are presented in Table 4-6,  and the  results of the chemi-
cal analyses  are presented in Table 4-7.
              The water balance for this system is presented in the
simplified  flbw diagram in Figure 4-9.   The water flow is given in.
                                47

-------
                                                       FLUE GAS FROM
                                                       FDS/UNPACKED
                                                       ABSORPTION TOWER
         INLET
         FLUE
         GAS
 BOOSTER
 FAN
                      REHEATER
                                                         STACK
      PACKED
    ABSORPTION
      TOWER/
     CYCLONIC
     DEMISTER

     (See Figure
        4-f
     for details)
         FLOODED
           DISK
         SCRUBBER
           (FDS)
                                    DEMISTER
                                    SPRAY WASH
                                  MAKE-UP
                                   WATER
                a
            FDS SLURRY
               TANK
                             1
                                             0
 TO  ASH
DISPOSAL
 POND
                             ABSORPTION
                             TOWER FEED
                                TANK
   TEST CONDITIONS
   • LIQUID-TO-GAS RATIO:  70.9 gal/1000 cu ft
   • FDS SLURRY TANK EFFLUENT SOLIDS:  15 PERCENT
   • COAL:  0.5 PERCENT SULFUR
   • ADDITIONAL CONDITIONS AT TIME OF SAMPLING
     SHOWN IN TABLE 4-6
Figure 4-8.
Typical flow diagram for Arizona Public Service Cholla
FDS and packed absorption tower scrubber system:
115 MW equivalent operation
                                  48

-------
     Table 4-6.  OPERATING CONDITIONS FOR ARIZONA
                PUBLIC SERVICE CHOLLA FDS AND
                ABSORPTION TOWER SCRUBBER SYSTEM
        Parameters
                                        Sample datea
4/1/74
11/7/74
Gas rate,
    cu m/sec
    acfm
Equivalent megawatts
SO- input, ppm
SO- removal,  percent
pH control
Dust input
    gm/cu m
    gr/scf
Absorption tower effluent
solids, percent
Liquid-to-gas ratio,
gal/1000 cu ft
  151
320,000
  115
  360
   75
  6.5
  0.41
  0.18
   15
  70.9
  151
320,000
  115
  360
   75
  6.5
  0.41
  0.18
   15
  70.9
 Data base used in extrapolation of scrubber system to 1000 MW
 equivalent size scrubber and for determining water balance.
 Water balance at time of testing is shown in Figure 4-9, and
 values extrapolated to 1000 MW equivalent are shown in Figure
 4-16.
                              49

-------
Table 4-7.  ANALYSES OF SCRUBBER LIQUORS FROM
            ARIZONA PUBLIC SERVICE CHOLLA FDS
            AND ABSORPTION TOWER SCRUBBER
            SYSTEM

Scrubber test conditions at time  of sampling shown in Table 4-6.
Concentration in milligrams per liter of filtered liquor (Whatman 40).

Scrubber
liquor
constituents

Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr) (total)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Molybdenum (Mo)
Nickel (Ni)
Potassium (K)
Selenium (Se)
Silicon (Si)
Silver (Ag)
Sodium (Na)
Tin (Sn)
Vanadium (V)
Zinc (Zn)
Total carbonate
Chloride (Cl)
Fluoride (F)
Sulfite
Sulfate
Phosphate
Total nitrogen
Chemical oxygen demand
Total dissolved solids
Total alkalinity
Conductance, mho/cm
Turbidity, Jackson units
pH
In-process data
Potential discharge data point
Sample location
Absorption tower tank
FDS tank
Sample date
4/1/74
0.06
0.03
<0.004
0.08
--
0.007
580
0.02
0.05
0.03
0. 17
0.02
T
0.30
0.007
_.
1.0
•--
1.0
1.7
0.01
800
--
--
o.oz
<1
6ZO
2.4
1.0
ZZOO
<0.1
<0.005
105
4300
52
0.0053
<5
6.59
11/7/74
2.1
0.16
0.02
<0.003
3.8
0.012
390
0.004
<0.01
0.01
0. 13
0. 15
9
0.48
<0.5
0.09
0.06
7.5
<0.033
--
<0.007
370
..
0.07
0.04
<1
760
1.0
21
1360
<0.1
<0.005
90
3300
130
0.00299
<5
6.80
4/1/74
2
0.09
<0.004
0. 14
--
0. Oil
680
0. 14
0.17
0.20
0.42
0.01
3
0.34
0.07

1.5
16
2.2
3.3
0.03
2250
..
_-
0. 11
<1
1700
0.7
0.9
4000
0.41
0.002
340
8700
--
0.0112
<5
3.04
11/7/74

0.22
--
0.04
8.0
0.044
770
0.024
0.1
0.16
8.1
0.37
4
2.5
<0.05
0.91
0.30
28
<0.001
--
0.05
1650
.-
0.67
0.47
<1
4200
1.5
3500
3750
<0.5
<0.005
390
14000
--
0.014
<5 '
3.38
                           50

-------
                                  49 gpm
                                                  STACK

MAKE-UP
WATER



19 gpm
0. 08%
10 gpm
O.S4%
t

i
32 gi
0. P
4500 gpm
19.8%

FLOODE
DISK
SCRUBB
(FDS)
AND PA
ABSORP
TOWER
pm
\%
} i
FDS S


:D
ER
CKED
TION
4493 <
19. 6
r
LURRY
NK
4 18'c^ฐno9pm 4 32 gpm
OU.U/fe I Q \Aฎ/
18,087 gpm
79.9%

xi_ FLUE
^~ GAS

LIMESTOM
ปP,m SLURRY



155 gpm
0.24%
MAKE-UP
WATER

E 0. 05%
"1
1
r
ABSORPTION
_ TOWFR — ^fc-
TANK


                 TO DISPOSAL
                    AREA
                          TEST CONDITIONS

                          • LIOUID-TO-GAS RATIO: 70.9 gal/1000 cu ft

                          • FDS SLURRY TANK EFFLUENT SOLIDS:
                            15 PERCENT

                          • COAL:  0.5 PERCENT SULFUR

                          • ADDITIONAL CONDITIONS AT TIME OF
                            SAMPLING SHOWN IN TABLE 4-6

                          • PERCENTAGE  VALUES ARE PERCENT OF
                            MAXIMUM WATER FLOW INTO SCRUBBER

                          • WATER FLOW RATE IN GALLONS
                            PER MINUTE (gpm).   TO CONVERT
                                     MULTIF
TO cu m/hr
IPLY BY 0.227
Figure 4-9.  Water balance for Arizona Public Service
             Cholla FDS and packed absorption tower
             scrubber system:  115 MW equivalent
             operation


                           51

-------
 gallons per minute, and the percentages are based on the maximum
 combined water flow to the two stages of scrubbing.
 4.2.4         Duquesne Light Company Phillips Station -- Single -
               and Dual-Stage  Venturi Scrubber System
               This system,  which is installed on the coal-fired
 boilers at the Phillips Station,  South Heights,  Pennsylvania,  is a full-
 scale system designed to treat 500 MW of power generating capacity
 in four parallel modules (Ref.  12).  Since each module is designed  to
 handle approximately 125 MW, the full plant capacity of 387 MW is
 expected to be handled with three modules; one would be  a spare.
 Three modules (Figure 4-10) are single-stage venturi scrubbers
 designed primarily for particulate removal; the fourth (Figure 4-11)
 consists of  a dual-stage venturi scrubber designed to remove fly  ash
 in the first  stage and SO2 in  the second stage.  All four modules were
 manufactured by  Chemico.  An SO- removal efficiency of about 60
 percent is obtained in the single-stage venturi scrubbers when a lime
 slurry is used as the absorbent; the efficiency is about 90 percent for
 the dual-stage unit.  A schematic of the design of the single-stage
 venturi scrubber is shown in Figure 4-12.
               Flue gases pass through mechanical and electrostatic
 dust collectors located in series with each boiler, then the gases are
 diverted into a common manifold with lines leading to each of the three
 single-stage scrubbers and the first stage of the dual-stage scrubber.
 The hot flue gas enters the first stage of the dual-stage scrubber or
 the single-stage scrubber and  impinges upon the upper cone where
half of the scrubber liquor is introduced (Figure 4-12).   The other
half of the scrubber liquor enters through the tangential nozzles at  a
point  above  the adjustable throat dampers.  The flue gas  and scrubbing
liquor make contact in the throat section of the scrubber  where the
particulates and some SO- are removed.  The gas and liquor continue
                                52

-------
            HOT FLUE GASES
            FROM DUST
            COLLECTORS
 SCRUBBER
 LIQUOR
 RECYCLE
 STREAM
DEMISTER/
 SPRAY  r~
 MAKE-UP
  PUMP
                I
SINGLE-STAGE
  SCRUBBER
(See Figure 4-12
for details)
                                  -WET OAS
STACK
           RECYCLE
            PUMP
                                 LIME SLURRY
                                    FEED
                              SUPERNATE
               INTERIM
               DISPOSAL
                 POND
      Figure 4-10.
          Typical flow diagram for Duquesne Phillips
          single-stage scrubber system
                                     53

-------
                      HOT FLUE GASES
                        FROM OUST
                        COLLECTORS
                            COLD FLUE GAS
         SCRUBBER
         LIQUOR
         RECYCLE
         STREAM
Ul
                                                                          DAMPER
                                                                          PURGE AIR
                                                                          BLOWER
                           SCRUBBER
                           LIQUOR
                           RECYCLE
                           STREAM
SPRAY
WATER
                       FIRST STAGE
                        SCRUBBER
                      (See Figure 4-12
                        for details)
                                          SECOND
                                           STAGE
                                         SCRUBBER
         DEMISTER
          SPRAY
                                                          DEMISTER
                                                           SPRAY
          MAKE-UP
           PUMP
                        OVERFLOW
                          FROM
                        CLARIFIER
                                                          RECYCLE
                                                           PUMP
                                          SECOND STAGE
                                             BLEED
                                                                                 LIME SLURRY
                                                                                     FEED
RECYCLE
 PUMP
                                                                            SERVICE
                                                                             WATER
                                                                  LIME
                                                                 STORAGE
                                                                  SILO
                                                                                            LIME
                                                                                            SLURRY
                                                                                            TANK
                                                       VIBRATOR
                                                     WEIGH FEEDER
                         INTERIM
                         DISPOSAL
                         POND
                                                                           LIME
                                                                          SLAKER
                                                               SLAKER
                                                               TRANSFER
                                                               TANK
                                                            LIME SLURRY
                                                               PUMP
                     Figure 4-11.   Typical flow diagram for Duquesne Phillips  Station
                                      dual-stage  scrubber  system

-------
                              HOT FLUE
                              GAS INLET
SCRUBBER
LIQUOR
RECYCLE
STREAM
                   TANGENTIAL
                 j- NOZZLES
               --- -•ป
                          ADJUSTABLE THROAT
                               DAMPERS
                                                         FLUE GAS
                                                           EXIT
         DEMISTER
           SPRAY
                                              LOWER CONE
                              TO RECYCLE
                                 PUMP
   Figure 4-12.  Schematic of Duquesne Phillips Station single-
                 stage scrubber
                               55

-------
downward to the separator section where the flue gas  enters a
demister, leaves the scrubber through a wet induced draft (ID) fan,
and enters the second stage of the dual-stage train, or through mist
eliminators in the three single-stage scrubbing trains.
               Scrubbing liquor leaves the scrubber to be  either re-
circulated or pumped to the clarifier.  The overflow from the clarifier
is recycled to the scrubber,  and the underflow is sent to one of three
interim disposal ponds.  Lime slurried with fresh water is added in
each scrubber and in the clarifier.  The pump and fan spray waters
also provide make-up water.
               On two occasions  slurry samples were taken from the
clarifier and scrubber and once from the pond.  The conditions that
existed in the scrubber at the time of sampling are given in  Table 4-8.
The results of the liquor analysis from these sample points  are pre-
sented in Table 4-9.  Clarifier underflow and pond supernate repre-
sent potential discharge points in this system.
               The water balance for this system is presented in the
simplified flow diagram in Figure 4-13 representing water flow under
operating conditions corrected for water imbalance caused by variances
from system design.   The water flow is given in gallons per minute,
and the percentages are based on the maximum water flow in the
system represented by the water flow to the scrubber.
4.3           EXTRAPOLATION OF PROCESS  FLOWS
4.3.1          Scale-Up of Four Systems Studied
               The actual flows of process liquors as  presented in
Figures 4-3,  4-6, 4-9, and 4-13 were used to calculate the process
flow expected for 1000 MW facilities operating at 90 percent SO-
removal efficiency, using the identical scrubber design, operating
conditions,  and coal as those  on which the data base was established.
In all cases, scale-up of flow rates was presumed to be proportional
                                56

-------
   Table 4-8.  OPERATING CONDITIONS FOR DUQUESNE
               PHILLIPS STATION: SINGLE-  AND DUAL-
               STAGE VENTURI SCRUBBER SYSTEMS
        Parameters
                                        Sample date'
10/4/73b
6/17/74c
Gas rate,
    cu m/sec
    acfm

Equivalent megawatts

SO_ input, ppm

SO_ removal, percent

pH control
Dust input

    gm/cu m
    gr/scฃ

Venturi effluent
solids, percent
Liquid-to-gas ratio,
gal/1000 cu ft
  274
580,000

  145

  1,400

  60

  6.0
  0.57
  0.25
  29.9
  236
500,000
  120
  1,400
  70
  6.0
  0.57
  0.25
  29.9
 Data base used in extrapolation of scrubber system to 1000 MW
 equivalent size scrubber and for determining water balance.
 Water balance at time of testing is shown in Figure 4-13,  and
 values extrapolated to 1000 MW equivalent  are shown in Figure
 4-17.

 Two single-stage scrubbers.
^ ^^
'Two single-stage and one dual-stage scrubbers.
                              57

-------
Table 4-9.  ANALYSES OF SCRUBBER LIQUORS FROM
            DUQUESNE PHILLIPS STATION:  SINGLE-
            AND DUAL-STAGE VENTURI SCRUBBER
            SYSTEMS

Scrubber test conditions at time of sampling shown in Table 4-8.
Concentration in milligrams per liter of filtered liquor (Whatman 40).




Scrubber
liquor
constituents
Aluminum (Al)
Antimony (Sb)
Arsenic (As)
Beryllium (Be)
Boron (B)
Cadmium (Cd)
Calcium (Ca)
Chromium (Cr) (total)
Cobalt (Co)
Copper (Cu)
Iron (Fe)
Lead (Pb)
Magnesium (Mg)
Manganese (Mn)
Mercury (Hg)
Molybdenum (Mo)
Nickel (Ni)
Potassium (K)
Selenium (Se)
Silicon (Si)
Silver (Ag)
Sodium (Na)
Tin (Sn)
Vanadium (V)
Zinc (ฃn)
Total carbonate
Chloride (Cl)
Fluoride (F)
Sulfite
Sulfate
Phosphate
Total nitrogen
Chemical oxygen demand
Total dissolved solids
Total alkalinity
Conductance, mho/cm
Turbidity, Jackson units
pH
In-process data
Potential discharge point data
Sample location

Scrubber effluent

Clarifier underflow
Sample date
10/4/73
..
--
0.085
0. 012
--
0.022
1300
0.037

0.06
_ _
0.08
220
--
0.09
..
--
20
0.8
--
0.02
1680
.-
.-
0.1Z
<1
1800
4.8
<1
4500
<0.05
<0.005
..
9400
61
0.0063
<3
9.20
6/17/74

--
0.06
0.002
--

660


--
_ _
0.5
--
--
0.0004
..
--
10
0.33
--
_ _
440
._
.-
--
<1
540
8
1.7
Z700
<0.05
<0. 005
65
4600
78
0.0033
<3
8.92
10/4/73
..
--
--
0.012
--
0.023
1400
0.040
	
0.07
0.026
0. 18
410
--
0.05
..
--
22
0.8
--
- -
2400


0.09
<1
2700
2.6
<1
6450
<0.05
<0.005
	
14000
--
0.01
<3
7.11
6/17/74
..
--
<0.004
0.003
--
_ _
600
	

--
..
0.4
--
-.
<0.002
	
..
26
0.028
--
.• .
320

	
--
<1
470
10
20
720
<0.05
<0.005
60
4200
--
0. 0034
<3
10.70

Pnnrf
* UI1U
supernate

6/17/74
..
--
<0.004
0.002
--
_ _.
600
	
	
--
..
0.4
_-
._
0.0004
_ _
	
22
0.095
--
..
344
_ _
	
--
<1
420
7
4.8
1000
<0.03
<0.005
	
4000
41
0.0030
<3
10.44
                           58

-------
                                          POND

                             TEST CONDITIONS
                             • LIQUID-TO-GAS RATIO: 29.9 gal/1000 cu ft
                             • SCRUBBER EFFLUENT SOLIDS:  5 PERCENT
                             • CLARIFIER UNDERFLOW SOLIDS:  38 PERCENT
                             • COAL:  2 PERCENT SULFUR
                             • ADDITIONAL CONDITIONS AT TIME OF
                               SAMPLING SHOWN IN  TABLE 4-8
                               PERCENTAGE VALUES ARE PERCENT OF
                               MAXIMUM WATER FLOW INTO SCRUBBER
                               WATER FLOW RATE IN GALLONS
                               PER MINUTE (gpm).  TO CONVERT
                               TO cu m/hr MULTIP
I PLY BY 0.227
Figure 4-13.  Water balance for Duquesne Phillips Station single'-
              and dual-stage venturi scrubber systems:  120 MW
              equivalent operation
                                 59

-------
to the flue gas flow rates; therefore, the power generated would be a
direct scale-up when identical coal was used.
               The scale-up of the scrubbing system based on the two
EPA/TVA Shawnee Steam Plant prototype facilities represents the
greatest size scale-up of the four facilities examined.  However, it
was assumed that individual scrubber modules of several hundred
megawatt capacity equivalence would be constructed for a large
power generating plant of this design rather than a single 1000 MW
unit.  Thus, the scale-up factor would probably be within the range of
10 to 30 times rather than a factor of two orders of magnitude.
Accordingly,  it was assumed that the relative flow rates would be
unaffected by the number of parallel units required to handle the full
plant capacity.  The scale-up of a scrubber  system based on an EPA/
TVA Shawnee venturi and spray tower or TCA type scrubber system
was determined on a linear proportional basis whereby the scrubber
liquid-to-gas ratio was held unchanged from those of the sampling
conditions.  The results of these calculations are presented in the
simplified schematic flow diagrams in Figures 4-14 and  4-15.
               For the Arizona Public Service Cholla Station scrubbing
system, full-scale scrubbers exist; thus,  the scale-up to 1000 MW
equivalent power generating capacity was  done on the presumption that
additional like-units would be added in parallel.  During  sampling
periods, the SG>2 removal efficiency of this system was 75 percent
although a scrubber module with a packed absorption tower removes
90 percent of the SO? (the absorption tower performing as a spray
tower is 60 percent efficient in SO2 removal).  In performing the
scale-up of this design to 90 percent removal efficiency,  it was
assumed that all scrubbers would operate at the  flow rates required
for a packed absorption tower. The results  of these calculations are
presented in the flow diagram in Figure 4-16.
                                60

-------
       VENTURI
       AND
       SPRAY
       TOWER
       SCRUBBER
    • PERCENTAGE VALUES ARE
      PERCENT OF MAXIMUM
      WATER FLOW INTO SCRUBBER
    • WATER FLOW RATE IN
      GALLONS PER MINUTE (gpm).
      TO CONVERT TO cu m/hr
      MULTIPLY BY 0.227
                    FILTER
                            1390 gpm
                              0.86%
                            >m
                                    POND
EXTRAPOLATED OPERATING CONDITIONS

• LIQUID-TO-GAS RATIO:  54.0 gal/1000 cu ft

• SCRUBBER EFFLUENT SOLIDS:  8 PERCENT

• CLARIFIER UNDERFLOW SOLIDS: 18 PERCENT

• FILTER CAKE SOLIDS:  45 PERCENT

• COAL:  3.4 PERCENT SULFUR

• S02 REMOVAL EFFICIENCY:  90 PERCENT

• TEST CONDITIONS USED AS BASIS FOR
  EXTRAPOLATION SHOWN IN TABLE 4-2
 Figure 4-14.
Water balance for venturi and spray tower
scrubber system (extrapolation based on
EPA/TVA Shawnee type of process):  1000
MW equivalent operation
                            61

-------
                    164,000 gpm
                       100%
          TCA
        SCRUBBER
             163,150 gpm
               99.5%
                                                   MAKE-UP
                                                   WATER
        LIMESTONE
        SLURRY
        REACTION
          TANK
 4800 gpm
   2.9%
    PERCENTAGE VALUES ARE
    PERCENT OF MAXIMUM
    WATER FLOW INTO SCRUBBER
    WATER FLOW RATE IN
    GALLONS PER MINUTE (gpm).
    TO CONVERT TO cu m/hr
    MULTIPLY BY 0.227
                                                       1490 gpm
                                                         0.9T
EXTRAPOLATED OPERATING CONDITIONS

• LIQUID-TO-GAS RATIO:  54.6 go I/1000 cu ft

• SCRUBBER EFFLUENT SOLIDS:  8 PERCENT

• CLARIFIER UNDERFLOW SOLIDS:  40 PERCENT

• COAL:  3.4 PERCENT SULFUR

• S02 REMOVAL EFFICIENCY:  90  PERCENT

• TEST CONDITIONS USED AS BASIS FOR
  EXTRAPOLATION SHOWN IN TABLE 4-4
  Figure 4-15.
Water balance for TCA scrubber system
(extrapolation based on EPA/TVA
Shawnee type of process):  1000 MW
equivalent operation

             62

-------
                                      430 gpm
                                       0.22%
190 gpm
 0.
MAKE-UP
 WATER
                       FLOODED
                       DISK
                       SCRUBBER
                       (FDS)
                       AND PACKED
                       ABSORPTION
                       TOWER
39,150 gpm
  19,9%

  295 gpm
   0.1?%
                                     157,500 gpm
                                        80.0%
                                                     STACK
                               MAKE-UP
                     157,410 gpm I  WATER
                       79.9r
                                        290
                                         0.
                             FLUE
                             GAS
                             39,000 gpm
                               19.8%
                                         LIMESTONE
                                         SLURRY
                       FDS SLURRY
                          TANK
                                    310 gpm
                                     0,16%
                                      0 gpm
                                      0,06%
                                  ABSORPTION
                                  TOWER
                                  TANK
                              520 gpm
                               0.26%
                       TO DISPOSAL
                          AREA
                              EXTRAPOLATED OPERATING CONDITIONS

                              • LIOUID-TO-GAS RATIO:  70.9 gal/1000 cu ft

                              • COAL:  0.5 PERCENT SULFUR
                              • S02 REMOVAL EFFICIENCY:  90 PERCENT

                              • FDS SLURRY TANK EFFLUENT: 15 PERCENT
                              • OPERATING CONDITIONS USED AS BASIS FOR
                                 EXTRAPOLATION SHOWN IN TABLE 4-6

                              • PERCENTAGE VALUES ARE PERCENT
                                OF MAXIMUM WATER FLOW INTO SCRUBBER

                              • WATER FLOW RATE IN GALLONS
                                PER MINUTE (gpm).  TO CONVERT
                                TO cu m/hr MULTIPLY BY 0.227
   Figure 4-16.  Water balance for FDS and absorption tower
                 scrubber system (extrapolation based on
                 Arizona Public Service Cholla  Station
                 process):  1000 MW equivalent operation
                                63

-------
               The Duquesne Phillips Station scrubbing system is
designed for about 400 MW operating capacity; thus, scaling up this
system to 1000 MW equivalent would require only about a 2. 5 increase
in scrubbing capacity.  However, at the time of  sampling,  flue gases
from only 120  MW generations capacity boilers were being treated,
but the full scrubber design capacity of three 125 MW equivalent
scrubbers was being used.  Also at that time, the flue gas velocity
through the collectors was  such that fly ash carry-over was four
times that normally experienced.  This higher solids content resulted
in an increase  in particulate loading which saturated the system's
design solids capacity.  To scale up this sytem to  1000 MW at 90
percent SCX  removal efficiency and to compensate for  the higher
solids loading, it was presumed that dual-stage  venturi scrubbers
would be required and deficiencies would be corrected.  As in the
other cases,  the scrubber liquid-to-gas ratio was assumed to be
unchanged from those of the test conditions.  The results of these
calculations  are presented in the simplified flow diagram in Figure
4-17.
4.3.2         Summary
               Table 4-10 summarizes and compares the water re-
quirements for the four scrubber systems studied and  extrapolated
in size to an  equivalent capacity of 1000 MW.  Several observations
can be made  from these comparisons relative to water use in SO,
                                                              L*
scrubbing systems.   The maximum water flow into  the scrubber
varies among the different types of scrubber systems and appears to
be unrelated  to the sulfur content of the coal, fly ash content,  or the
percentage of the scrubber's design capacity being used.  Since the
scrubber liquor requirement appears to be solely a function of
scrubber system design,  no extrapolation of water use from a given
system to other systems or other sulfur content coals  is possible
                                64

-------
                                          790 gpm
                                           0.6%
              121,400 gpm
                 95.6%
950
 0.
LIME
SLURRY
                                                           STACK
                           DUAL -STAGE
                            VENTURI
                           SCRUBBER
                      200 gpm
                                         5400 gpm
                                           4.3%
                                5560 gpm
                                  4.4%
                                           1
                                        CLARIFIER
                                130 gpm
                                 O.f%
                                          POND


                      EXTRAPOLATED OPERATING CONDITIONS

                      • LIQUID-TO-GAS RATIO:  29.9 gal/1000 cu ft

                      • SCRUBBER EFFLUENT SOLIDS:  5 PERCENT
                      • CLARIFIER UNDERFLOW SOLIDS:  38 PERCENT
                      • COAL:  2 PERCENT SULFUR

                      • S02 REMOVAL EFFICIENCY:  90 PERCENT

                      • OPERATING CONDITIONS USED AS BASIS FOR
                        EXTRAPOLATION SHOWN IN TABLE  4-8

                      • PERCENTAGE VALUES ARE PERCENT OF
                        MAXIMUM WATER  FLOW INTO SCRUBBER

                      • WATER FLOW RATE IN GALLONS
                        PER MINUTE (gpm).  TO COVERT
                        TO cu m/hr MULTIPLY BY 0.227
      Figure 4-17,
         Water balance for dual-stage venturi
         scrubber system (extrapolation
         based on Duquesne Phillips Station
         type of process):  1000 MW equivalent
         operation
                                65

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Table 4-10.  SUMMARY AND COMPARISON OF WATER BALANCE PROJECTIONS
            FOR 1000 MW EQUIVALENT SCRUBBERS
                    Values based on 90 percent SO-, removal
Scrubber location,
type, and
absorbent
Water balance
shown in
Extrapolation
base
Sulfur in coal,
percent
Flow points
Scrubber
Input
Output
Bleed
Clarifier
Overflow
Underflow
Filter
Filtrate
Filter cake
Water losses
Stack
Pond
Water input
With absorbent
Make-up
TVA Shawnee,
venturi and
spray, lime
Figure 4-14
8.3 MW equiv. ,
83% loading,
8 5% SOฃ removal
3.4
Water
flow,3
gpm

163,000
162, 100
4,800

2,900
1,900

1,390
510

900
510
500
910
Percent
of total
flow

100
99.5 *
Z.95

1.78
1.17

0.86
0.31

0. 55
0.31
0.30
0.56
TVA Shawnee,
TCA, limestone
Figure 4-15
6.8 MW equiv.,
68% loading,
86% SO2 removal
3.4
Water
flow,a
gpm

164,000
163, 150
4,120

3,310
810

Percent
of total
flow

100
99.5
2.5

2.0
0.5

Not
Applicable

850
810
170
1,490

0.5
0.5
0. 1
0.9
Arizona Cholla,
FDS and absorption
tower, limestone
and fly ash
Figure 4-16
115 MW equiv.,
100% loading,
75% SO2 removal
0.5
Water
flow,a
gpm

196,840
196,410
520

Percent
of total
flow

100
99.8
0.26

Not
Applicable


Not
Applicable

430
520
110
840

0.22
0.26
0.06
0.43
Duquesne Phillips,
dual-stage venturi,
lime
Figure 4-17
120 MW equiv.,
33% loading,
65% SO2 removal
2.0
Water
flow,a
gpm

127,750
126. 960
5,560

5,400
490

Percent
of total
flow

100
99.4
4.4

4.3
0.4

Not
Applicable

790
360
1, 150
--

O.fe
0.3
0.9
--
aTo convert gpm to cu m/hr multiply by 0.227.
Values of Arizona Cholla are for FDS slurry tank rather than scrubber.

-------
from these data.  Moreover, based on the operating procedures at the
time of sampling, it was presumed that the liquid-to-gas ratios within
a scrubber would be maintained constant so as to obtain the desired
sulfur  removal efficiency.  Thus,  an extrapolation to power plant load
factors other than those observed during sampling would be expected
to be a reasonably linear  function.  No other variables or conditions
appear to affect the scrubber water requirements.
              Table 4-11  summarizes the flows of the liquor bleed
streams. In the bleed  stream from the  scrubber, the larger streams
come from the higher sulfur bearing coals; however,  a direct
correlation is impossible because of the fly ash content variation in
the solids and the total  solids content in the slurry.  Comparison of
water loss to the pond is also impossible because of the different
sludge disposal  designs among the plants.
              An analysis was made to establish a scaling factor that
could be used to correlate the  ratio of water loss to the pond (based on
a 1000 MW equivalent scrubber capacity) as a function of the sulfur
content of the coal being burned.  However,  to establish this factor
two normalizing assumptions were made:
         a.    The sludge from the scrubber would be dewatered
              to a solids content of 45 percent solids by weight.
         b.    All available  supernate from the dewatering pro-
              cess would be returned to the scrubber system.
On the basis  of these two assumptions, it was found that for the four
scrubber systems studied the ratio of F/S is  between 150 to Z24 with
an average of 187, where F  is the water loss to the disposal site in
gallons per minute (to convert to cu m/hr multiply by 0. 227) and S is
the percent sulfur in the coal.
             • In a given  system,  a reduction in sulfur content with
all other system parameters held constant will have the  effect of .
reducing the quantity of solid waste and the waste water  associated
                                 67

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Table 4-11.  SUMMARY OF SCRUBBER BLEED STREAM
            FLOW PROJECTIONS FOR  1000 MW
            EQUIVALENT SCRUBBERS

       Values based on 90 percent SO2 removal

Scrubber location.
type, and
absorbent
Water balance
shown in
Coal type and sulfur
content, percent
Scrubber capacity,
MW
Extrapolation base,
MW
Sulfite and sulfate
in total solids,
percent
Scrubber
Bleed stream,
gpmc
Solids, percent
Clarifier
Underflow, gpm
Solids, percent
Filter
Water loss in
cake, gpm
Solids in cake,
percent
Filtrate, gpm
Solids, percent
Pond
Supernate,
gpm
Solids, percent

TVA Shawnee,
venturi and spray
tower, lime
Figure 4-14
Eastern 3.4
10
8.3

50


4800

8

1900
18d

510

4 5

1390
45

Not
Applicable



TVA Shawnee,
TCA, limestone
Figure 4-15
Eastern 3.4
10
6.8

50


4120

8

810
40



Not
Applicable



Not
Applicable

Arizona Cholla,
FDS and absorption
tower, limestone
and fly ash
Figure 4-16
Western 0.5
120
115

40*


520

15

Not
Applicable



Not
Applicable



Not
Applicable


Duquesne Phillips,
dual- stage venturi,
lime
Figure 4-17
Eastern 2. 0
Four units of
125 each
120

40a


5560

5

490
38



Not
Applicable



130

<1
Adjusted to 90 percent SO, removal efficiency.
Values for Arizona Cholla are for FDS slurry tank rather than scrubber.
Water flow rate in gallons per minute; to convert gpm to cu m/hr multiply by 0.227.
Clarifier was undersized resulting in shorter residence time and lower solids content.
                        68

-------
with the solids.  The reduced loss of waste water to the disposal site
will reduce the volume of make-up water required to balance the
system.  However, if this reduction is sufficiently large so as to be
inadequate to satisfy minimum fresh water requirements, a system
imbalance  may occur.  In this case,  when minimum fresh water
requirements are  met, make-up water will then exceed water losses
by evaporation or  to the pond and excess system water will result.
Two potential environmentally acceptable solutions exist:  (a)
increase the relative quantity of waste water being disposed with
solids,  or  (b) treat a portion of the return water from the dewatering
treatment  circuit  to satisfy the fresh water requirement.  In many
cases, the need for  fresh water can be reduced by blending untreated
return water with fresh  water,  but there is a limit to the extent that
blended water can satisfy the demister or pump seal fresh water
requirement. This  limit is  a system design parameter for each
plant and must be found  by experience.
         The make-up water requirement for each system is depend-
ent primarily upon the water balance from pond losses and stack
losses.  However, in watertight systems, the water balance require-
ment for make-up water may be exceeded by the fresh water require-
ments of the demister and pump seals.  In these cases,  the limit to
the degree of dewatering may be dictated by this fresh water require-
ment, and there may exist only a slight accommodation for reducing
the sulfur  content without major system design changes.  Since stack
losses are dependent upon atmospheric conditions and design
variables, adjustments  in this value are not easily made; therefore,
it is not an adjustable parameter.
               In  addition to a change in sulfur content as it affects
the water  balance, an .identical effect is experienced with  a decrease
in flue gas mass loading to the scrubber.  In a case of reduced load
factor, as before, a reduction  in sulfur waste products causes a
                                 69

-------
reduction in waste water and in make-up water to meet water balance
requirements. As before, if this reduction exceeds the fresh water
requirements of the system, an identical water balance problem
arises.
4.4           CHEMICAL CONDITIONS AFFECTING COMPOSITION
              OF SCRUBBER LIQUORS AND WATER IMBALANCE
              In each case of water imbalance previously identified,
excess system water occurs only when fresh water requirements
exceed make-up water requirements and can take place whenever a
critical reduction in water losses occurs.   Other system variations
beside those identified here are possible,  but the point at which
excess system water is produced can not be determined without
detailed study of the system design or by experimental determination.
It could not be determined from these  data whether sulfur removal
efficiency or other specific design parameters could produce inde-
pendently the conditions necessary for excess  system water.
              The following sections  (4.4. 1 and 4.4.2) provide the
results of an overview of fundamental  scrubber chemistry and the
potential for water imbalance.
4.4.1         Saturation Concentrations and Solubility of
              Ingredients
              An evaluation of the scrubber liquor chemical analysis
(shown in Tables  4-3,  4-5,  4-7,  and 4-9) indicates that the scrubber
systems operate at saturation concentrations of calcium and sulfate
ions amounting to several thousand milligrams per liter.  In addition,
sodium and chloride ions  were found to be present in high concen-
trations, but they are not controlled by saturation conditions.
              The  analytical data for  the liquor samples are con-
sistent with the assumption of saturation with gypsum (CaSO^  • 2H_O).
                                70

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However, it  should not  be inferred that the concentrations of cal-
cium or sulfate will not vary among  the  liquor samples, nor will
the solubility of calcium sulfate (as expressed by the product of the
sulfate and calcium concentrations) remain constant.  In addition to the
effect of temperature, the solubility of calcium  sulfate is affected by
the presence of other ions (e.g.,  sodium,  magnesium, or chloride).
Although the quantitative relationship is somewhat complicated,  in
general the solubility of calcium sulfate will increase by the summation
of all molar  ionic concentrations after each has been multiplied by the
square of its ionic charge.  Therefore, magnesium  ions have a four-
fold greater  effect than equimolar  concentrations of either sodium or
chloride ions.  An approximate correlation may be observed between
the solubility of calcium sulfate and the total dissolved solids (TDS) of
the sample.  For  example, each of the three data sets for the EPA/TVA
Shawnee-venturi system shows a fivefold increase in the product of the
calcium and  sulfate concentrations which corresponds to a threefold
increase in TDS.  Similar relationships exist in each of the other
scrubbing systems.
               The chemistry of other chemical constituents including
the trace elements in the system are controlled by their saturation
concentrations in  the presence of calcium,  sulfate,  and hydroxyl ions.
Trace elements, including toxic species,  tend to be limited by their
equilibrium concentration with the calcium and  sulfate ions at low values
of pH and with the hydroxyl  ions at high values of pH. Most of these ele-
ments are  controlled in the  scrubber liquor at concentration levels be-
low 1 mg/t , and many are controlled at about 0.05 mg/1 .
               Control of highly soluble species is dependent upon
maintaining steady-state conditions whereby the system's rate of loss
(as soluble species  in occluded water associated with solid waste)
balances the rate  of intake (either by absorption from flue gas or f-rom
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process ingredients).  The tighter the closed loop, the higher the
specie concentrations become.  The most direct effect of these
species is their contribution to the TDS.  In  each case,  sodium,
calcium,  sulfate,  magnesium,  and chloride ions constitute the mea-
surable dissolved solids content in the liquors.  High TDS values
increase the ionic strength of the liquor which in turn increases the
saturation concentrations  of chemically controlled soluble species in
the system.
               The concentration of soluble species in the scrubber
liquors is  dependent upon  two  system variables: the pH of the system
liquors, and the tightness of the water balance within the system.  The
latter will affect the TDS, and the calcium sulfate chemistry control
will be  affected by both.
               In addition  to these system variables, a reduction in
the coal's  sulfur content will increase the soluble species in the scrub-
ber.  In this case, the rate of production of  sulfur by-products is re-
duced.  As a consequence, the scrubbing of other salts and acids from
the flue gas is proportionately greater and will  result in higher soluble
salt contents.  The  resulting increase in ionic strength will also in-
crease the soluble saturation concentration of calcium sulfate.  In
some systems, the  increase of soluble  calcium  sulfate will increase
the demister scaling problem.  In all cases, an independent reduction
in sulfur content will increase the level of dissolved solids in the liquor
relative to higher sulfur operation.
4.4.2         Water Imbalance
               A reduction in boiler load factor  decreases the flue gas
mass flow  but does not affect the water quality of the liquor.  In this
case, absorption of all species from the flue gas (or from fly ash
carried in the flue gas) is  reduced in direct proportion to the reduc-
                                                                •
tion in flue gas mass flow. The rate of production of sulfur by-products
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is reduced proportionately to all other system rates; thus,  no change is
effected in the concentration of soluble species in the liquor.  In both
the cases of reduced load factor and reduced sulfur content, it has been
assumed that the reduced need for make-up water to satisfy water
balance remains sufficient to satisfy the minimum requirement for
fresh water make-up.
              The chemical analysis of system liquors reveals that
the chemical constituents within these liquors  exist at essentially
identical concentrations at all potential system purge points.  Minor
variations exist as a  consequence  of the design choice of make-up
water introduction or absorbent introduction into the system, but these
variations do not affect the  general water quality of the liquor.  The
exception to this generalization exists between scrubber effluent  and
points past the introduction of the absorbent.  The scrubber effluent
has a slightly lower pH than the system downstream of the reaction
tank and concentrations of species controlled by the hydroxyl ion tend
to be somewhat  higher.  Since scrubber effluent is not a potential
point of  system purge,  it need not be considered for  water quality
acceptance.
4.5           ASSESSMENT
              Table 2-1  shows the range of concentration  of the  con-
stituents found in the scrubber liquors at the potential discharge
points, the criteria assumed for the quality  of nonpotable service
water for usage in the power plant,  and a tabulation of the  October
1973 EPA proposed criteria for public water supply intake. It pre-
sents the  total range of values of the ingredients found in the liquors
at the potential purge points among the four  systems studied.  This
range of constituent values  depends  upon the composition of the coal
and absorbents used,  the scrubber design,  and system operating
characteristics.  The values in the table are given in milligrams
                                73

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per liter; however, the potential discharge rate in pounds per day can
be calculated from the following equation:

                           DR = 0.012 cf

where
      DR = discharge rate of the ingredient in Ib/day (to
           convert Ib/day to kg/day multiply by 0.4536)
        c = concentration of the constituent in mg/i
        / = flow rate of the water in the scrubber system
           flow streams  in gpm

               For example, a given constituent at 0.004 mg/i at a
flow rate of 400 gpm would mean about 0.009 kg/day (0.019 Ib/day)
of material potentially would be discharged.
               An assessment was made of the potential water uses and
the constituents of concern for each use; the  results are summarized in
Table 4-12.  There is a need for large quantities of nonpotable water
for general operations within the power plant (listed under "Service
water" in Table 4-12) and for other applications that require water free
of constituents that would corrode,  scale, or foul the equipment.  Al-
though the concentration of many constituents does not present a problem
for scrubber liquors to satisfy these needs, it is necessary to reduce
the concentration levels of the chloride,  sulfate, magnesium, and
calcium  present from one or more of the liquor streams studied.
               A treatment process such as lime-soda softening will
reduce the sulfate, magnesium,  and calcium concentrations to pre-
clude scaling of the equipment.   In addition, the concentrations of
arsenic (As), boron (B),  cadmium (Cd),  iron (Fe),  lead (Pb),
selenium (Se),  mercury (Hg), copper (Cu), zinc (Zn), nickel (Ni),
                                74

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         Table 4-12.  POTENTIAL WATER USES AND
                      CONSTITUENTS OF CONCERN
          Water use
     Constituents of concern
Service water

     Scrubber make-up

    Air conditioning
    equipment

    Pump seals

    Cooling tower make-up

    Evaporative coolers

    Housekeeping
Discharge
Calcium, magnesium, and sulfate
Calcium, chloride, magnesium,
sulfate,  and total dissolved
solids
Arsenic, boron, cadmium, chlo-
ride, chromium (total), fluoride,
iron, lead,  manganese, mercury,
selenium,  silver, and sulfate
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cobalt (Co), and manganese (Mn) will also be reduced by this process.
In existing or new plants where brackish water is acceptable for
service water use this process would be adequate.  In cases where
brackish water is unacceptable, the lime-soda softening process
would have to be followed by an additional process such as reverse
osmosis.   Furthermore,  a high chloride content water requires that
the equipment in contact with this water be constructed  from,  or
coated with,  salt water resistant materials.  Although it is within the
current state of the art to build chemical process equipment to with-
stand the corrosive effects of high chloride content water,  the equip-
ment costs will be increased.  Chlorides can be removed from the
scrubber liquor by the use of reverse osmosis, ion exchange, or
evaporation and condensation techniques.  These techniques, in
addition to other concepts  such as electrodialysis and vacuum
freezing vapor compression, are being tested in many parts of the
world as methods for converting sea water to potable water.
              If the scrubber  liquor is to be discharged to surface or
ground waters and is to meet the October  1973 EPA-proposed criteria
for public water supplies,  the  concentration of the following con-
stituents will have to be reduced for some of the cases studied:  As,
B,  Cd, chromium (Cr)  (total), fluoride, iron, Mn,  and  silver (Ag).
In addition, it was found that Pb, Hg,  Se,  chlorides,  and sulfates  in
the scrubber liquor from all four power plants exceeded the criteria.
The amount of reduction of the constituents will depend  upon the spe-
cific composition of  the scrubber liquor.  For example, analyses  of
the individual power plant  scrubber liquors showed that the Arizona
Public Service Cholla Station scrubber at  the time of sampling was
operating in a tightly closed scrubber loop condition resulting in higher
than acceptable  concentration levels in the discharge  stream from the
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FDS tank for all of the aforementioned ingredients,  except As.  The
EPA/TVA Shawnee TCA scrubber system exceeded the limits for As,
Cr (total), Pb, Hg, Se, Ag, chlorides, and sulfates.  The EPA/TVA
Shawnee venturi and spray tower scrubber system exceeded the limits
for As, B, Cd, Cr (total), Pb, Mn, Hg, Se, Ag, chlorides, and sul-
fates in the discharge from the clarifier underflow or from the drum
vacuum filter filtrate on one or more of the sampling dates.  Con-
versely, the  Duquesne Phillips Station system was experiencing oper-
ating conditions requiring high water flow rates through the system
which diluted the concentration of the dissolved ingredients.  The re-
sult was that the  liquor from the clarifier underflow exceeded the
proposed EPA criteria only for Cd, Pb, Hg,  Se, chlorides, and sul-
fates; these results may not represent the normal concentrations to
be expected in this scrubber liquor.
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                            SECTION 5
                  WATER TREATMENT STUDIES

5.1           LITERATURE AND INDUSTRY REVIEW
              The domestic and foreign literature was reviewed, and
technical meetings and discussions were held with representatives
from water treatment processors,  consulting firms,  equipment manu-
facturers, research laboratories, and governmental agencies conduct-
ing research and development testing in the field of water treatment.
This review was conducted to  determine what data are available on
processes and types of equipment for use in reducing the concentra-
tion levels of the sludge liquor constituents (Refs. 13 through 50).  The
results indicated that there are many pieces of equipment available
designed to accomplish a specific water treatment and that numerous
laboratories, agencies, and companies are currently engaged in ex-
panding the field of water chemistry and treatment operations.  How-
ever, most of this work is being  directed toward the treatment of brine
or fresh water for public use  or a specific industrial process, and for
sanitary waste disposal; only  a limited amount of work has been done
in industrial water  reuse.
              Generic types of water treatment processes and an in-
dication of their current status is given in Table 5- 1.  Also included is
an assessment,  which is based upon the data gathered in the technical
review, about the possibility of the treated water meeting the established
water  quality criteria for reuse or discharge. A selection of the systems
considered and applicable for scrubber liquor treatment is given in
Section 5. 2.
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Table 5-1.  SUMMARY OF GENERIC TYPES OF WATER
           TREATMENT PROCESSES CAPABLE OF
           MEETING WATER QUALITY CRITERIA
Water treatment
process
Complete system
Multistage evaporation
Tower distillation
Brine concentration
Spray drying
Vacuum freezing
Solar distillation
Rotating bipolar electrodes
Partial operation
Filtration or centrifugation
Ultrafiltration
Reverse osmosis
Ion exchange
Chemical precipitation
(including lime -soda
softening)
Electrodialysis
Selective absorbent
Electrochemical; fluidized
bed
Foam separation
EPA-proposed
public water
supply intake,
October 1973

Yes
Yes
Yes
Yes
Yes
Yes
No

No
No
Yes
Yes
No
Yes
No
No
No
Nonpo table
service
water

Yes
Yes
Yes
Yes
Yes
Yes
No

No
No
Yes
Yes
Yes
Yes
No
No
No
Status

Operational
Operational
Operational
Operational
Development
Development
Laboratory

Operational
Operational
Operational
Operational
Operational
Development
Laboratory
Laboratory
Laboratory
Used with other operations to form a total water treatment system
                         80

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5.1.1         Multistage Evaporation
              Many concepts and designs of single- and multistage
evaporators are available and have been used in the chemical process
industry for many years to concentrate the  solids in a liquid mixture
by evaporation of the liquid material  (Ref. 13).   Multistage  evap-
oration uses the concept of a series of evaporators with decreas-
ing pressure from one  stage to the next;  the  vapor from one stage
is fed into the heating chamber for the following stage.  This evapora-
tion and condensation concept can produce a condensate of high purity
water that meets the  requirements for discharge to bodies of water,
for potable water, or for direct use as  boiler feed water. Multistage
evaporation was one of the first techniques  used for desalting sea water
for drinking water and is still being used.  An efficient multistage
evaporator design using flash evaporation was evaluated in this study
(see Section 5.2.4).
5.1.2         Tower Distillation
              Tower distillation could be used for water purification,
and the distillate would be of potable or boiler feed quality (Ref. 13).
However, unless there are special circumstances  (e.g., a supply of
excess heat or steam available and a need for potable water) this is
not a cost-effective approach for obtaining  discharge or  service water.
The cost for distilled water is higher than condensate water from a
multistage flash evaporator.
5.1.3         Brine Concentration
              Brine concentration uses a type  of falling film evapora-
tor wherein the feed brine falls in a film inside a tube bundle,  and a
portion of this film is then vaporized (Refs. 14 and 15).  There is also
a vapor-compression thermodynamic cycle in which the vapor is com-
pressed and introduced to the shell side of the  tube bundle. The
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 temperature differential between the vapor and the brine film causes
 the vapor to condense as pure water.  The concentrated brine solution
 is withdrawn to a disposal pond. The condensate meets the discharge
 or power plant reuse water quality criteria.  The results of a techni-
 cal and economic evaluation on  the potential use  of a brine concentrator
 for treating the scrubber liquor are given in Section 5.2. 5.
 5.1.4         Spray Drying
               Spray dryers are similar to flash evaporators.  A
 material is sprayed into a  vacuum  chamber, the liquid is evaporated,
 and the particulate matter  is collected in the base of the dryer.  This
 equipment is generally used for removing moisture from solid par-
 ticles that are  considered the product rather than vice versa (Ref. 13).
 Consequently,  this specific process was not examined as a potential
 water treatment operation  although the condensate would be a high-
 quality water.  However, a combination  of a modified multistage
 evaporation and spray drying called multistage flash evaporation was
 evaluated (see  Section 5.2.4).
 5.1.5         Vacuum Freezing
               In the vacuum freezing vapor-compression process,
 latent heat of fusion is given up  when precooled feed water is intro-
 duced into  a chamber under low pressure.  The feed water is pumped
 into the system through a deaerator and  then through heat exchangers
where it is cooled to the freezing temperature by cold brine and cold
product water leaving the system.  The deaerated and cooled feed
water is subsequently pumped into the freezer where a simultaneous
boiling-freezing process occurs.  The low pressure causes the water
to boil and part of it vaporizes.  The vapor extracts heat of vaporiza-
 tion from the remaining feed water, part of which then freezes.  The
ice-brine slurry is transferred  from the freezer to  a washer to re*
move adhering  brine and in turn is  sent to a melter. This process is
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reported to be in a development stage for use in desalting sea water
(Refs. 16 and 17).  However, an investigation into the adaptability
of this process for producing discharge or service water from desul-
furization slurry liquor indicated that additional developmental tests
must be made before using this technique.
5.1.6        Filtration or Centrifugation
              Filtration or centrifugation, which is a mechanical
separation process that can remove particles from a feed water source,
is ineffective on dissolved ingredients  (Refs. 18 through 20).  Conse-
quently,  this process must be considered for use only in conjunction
with other processes capable of removing the dissolved constituents
from the water.
5.1.7        Ultrafiltration
              Ultrafiltration or microfiltration uses  membranes of
pore  size  ranging from 0.001 to  10 microns  to  achieve separation
of impurities in waste water on the basis of molecular  size only.
This  filtration process  removes smaller  particles from the liquor
to be treated than normal filtration or  centrifugation, but it does
not reduce the  concentration levels of dissolved constituents such
as the chloride  salts.  Although Ultrafiltration processes are oper-
ational,  the application is for removal of suspended solids, coliform
bacteria, and similar particle type contaminants in sewage waste
water.
5.1.8        Reverse Osmosis
              Osmosis oc.curs when pure water and a salt solution are
on opposite sides of a semipermeable membrane and pure water dif-
fuses through the membrane  diluting the  salt solution (Refs. 16, 17,
and  21 through 26).   The osmotic process  can be reversed by  .
applying pressure [>30 kg/sq cm ฃ>420 psi)] to the  salt solution.
                                  83

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This process has been successfully used for desalting sea water and
can be used to treat scrubber liquors for discharge or reuse.  The

results of an economic evaluation of this technique following a pre-
treatment of lime-soda softening are discussed in Section 5.2.2.

5.1.9         Ion Exchange

              Demineralization or ion exchange is based on the re-

moval of the impurities from water by means of synthetic resins that

have an affinity for dissolved or ionized salts.  The exact types of

resins to be used will depend upon the specific constituents to  be re-

moved (Refs. 16,  17, and 26 through 29).  An economic analysis was
made of the ion exchange process in conjunction with the lime-soda

softening process  (see Section 5.2.3).  Work is under way by many

researchers to develop resins that will selectively remove specific

ions and trace metals from water solutions.  Five examples for heavy

metal removal are:

        a.    Chelex-100  resin is reported to concentrate cadmium
              (Cd), cobalt (Co),  chromium (Cr), copper (Cu), lead
              (Pb), manganese (Mn), nickel (Ni),  and zinc (Zn) in
              preference to  calcium (Ca), magnesium (Mg), potas-
              sium (K), and sodium  (Na).   A pH controlled solution
              of 5 to 6 is required.

        b.    Amberlite EX 318 resin at a pH of >4 selectively con-
              centrates Cd,  Co,  Cu, iron (Fe), mercury (Hg), Ni, Pb,
              vanadium (V), and  Zn.
        c.    Titanium  arsenate  selectively removes Cd, Co, Cu, Mn,
              Ni,  Pb, tin  (Sn), and Zn.

        d.    Permutit  S 1005 resin at a pH of 5 to 9 is reported to
              remove Cd, Co, Cu, Mn, molybdenum (Mo), Ni, Pb,
              V and Zn  from a water solution.

        e.    Rohm and Haas EX 243 is being used to remove boron
              (B)  from a magnesium chloride brine solution.
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5.1.10        Selective Absorbent
              Laboratory work is progressing on identifying absorbents
that have an affinity for specific ions or heavy metals (Refs. 29 through
31).  An example is tannery hair  chemically treated to form the sulfhy-
dryl and used as packing in a column.  Silver (Ag), Cd, Cu, Hg, and Zn
will be absorbed from a water  solution passed through the column.
              Activated carbon is widely used for removing organic
impurities from waste water, and work is under way to determine if
activated carbon  can be used effectively for removing inorganic sub-
stances.  Manganese is reported to  be removed from water by the
spray aeration of the water to oxidize the manganese and form a pre-
cipitate; this is followed by filtration and absorption with activated
carbon.  However, the use of selective absorbents has not progressed
sufficiently for it to be considered an economically available process
for treating scrubber liquor.
5.1.11         Chemical Precipitation (including lime-soda
               softening)
               Chemical precipitation is an all encompassing term for
reacting ingredients together to form a chemical compound that will
precipitate from the water  solution  (Refs.  32 through 43).  A commonly
used example of chemical precipitation is the reaction of lime and  soda
ash with calcium and magnesium salts to reduce the hardness of water.
Section 5.2. 1 presents the  results of an evaluation of using a lime-soda
softening  operation for treating scrubber liquors.  All chemical pre-
cipitation processes require a separation operation to remove the pre-
cipitates from the liquid.
               Considerable research is  also under way to develop
chemical reactions that  will selectively remove heavy metals from a
water solution.  For example, in tests at the Central Contra Costa,
County, California, Sanitary District Treatment Plant it was shown
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that a process using the addition of calcium hydroxide to water to
attain a pH of 11.5 followed by settling, recarbonation with carbon
dioxide to lower the pH to a range of 9ป 5vto 10.5 and subsequently
filtration, reduces the concentration of Ag, barium (Ba),  Cd, Co,
Cr, Cu, Mn, Ni,  Pb, and Zn in the water.  In a similar process,  the
Orange County Water District, Santa Ana,  California, is using a treat-
ment process consisting of operations such as coagulation with ferric
sulfate and a lime-soda softening to reduce the concentration of heavy
metals in their sewage water reuse treatment plant.
              At the EPA Water Supply Research Laboratory, National
Environmental Research Center, Cincinnati,  Ohio, laboratory tests
have confirmed the reduction in concentration of arsenic (As), Ba, Hg,
and selenium (Se) as the result of coagulation with ferric sulfate and a
lime softening operation at a pH of 11.
              Some other chemical reactions include:
         a.    Thioacetamide in water at a pH of 1 is reported to
              precipitate Cd, Cu,  and Pb, and at a pH  of 8 to pre-
              cipitate Cr, Mo, titanium (Ti) and Zn.
         b.    Metal sulfides such as  CdS2 at a pH of 2. 5 will pre-
              cipitate Co, Cr,  Cu,  Mo,  Ni,  and V from water.
         c.    Chelation with ammonium pyrrolidine dithiocarbonate
              at a pH of 4. 5 to 6 is reported to remove Cd,  Co, Cu,
              Mn, Mo, Ni,  Pb,  and Zn.
         d.    Dibromo-oxime (dibromo-hydroxy-quinoline) with
              acetone in brine water  at a pH of 5 to 8 is reported
              to precipitate Co, Cr,  Cu, Mn,  Pb, and  Zn.
         e.    The addition of aluminum sulfate will precipitate As,
              Cr,  Cu,  Pb,  Se, and Zn from  a water solution at a
              pH of 6.8 to 7.
         f.    Calcium hydroxide at a pH of 9. 5 will cause precipi-
              tation of Co,  Cr, Cu, Mn, Ni, Pb,  and Zn from water,
              and dolomite limestone of 40 to 70 percent calcium
              hydroxide and 30 to 60  percent magnesium hydroxide
              added to water will precipitate Pb and Sn.
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        g.    Coagulation with ferric sulfate at a pH of 9 to 11 will
              remove As from the water,  and at a pH of 6 to 9 Se
              will be removed.   At a pH of about 7 to 8 and followed
              by air injection, filtration,  and magnetic attraction of
              the ions, it is reported that antimony (Sb), Cr,  Cu,
              Fe, Hg, Ni, and Pb can be removed from water.
        h.    Starch xanthate mixed with a cationic polymer (such
              as polyvinylbenzyl trimethyl-ammonium chloride)  into
              a water solution containing heavy metals  is reported
              to precipitate both the polymer and the heavy metals
              as a cohesive floe.  This  process  will remove Ag, Cd,
              Cr, Cu, Fe,  Hg, Mn,  Ni, Pb, and Zn.
5.1.12        Electrochemical; Fluidized Bed
              Laboratory tests are being  made on a method of
removing trace heavy metals from a water-lime solution with a pH
of 7 to 8 by applying a low voltage direct current field across  a
fluidized bed of  conductive particles.  The metallic impurities plate
out on the tin granules that are used as the collector particles.
Arsenic,  Cd,  Cr, Cu, Hg, and Zn were reported to be reduced  in
concentration by this operation.  This process will not  remove the
chlorides from the water; a  reverse  osmosis or other process must
be used in conjunction with  this method  (Ref. 44).
5.1.13       Rotating Bipolar Electrodes
              A process is  being studied  in the  laboratory in which
bipolar electrodes are rotated in a central chamber containing water.
The cations in the water are attracted toward the negatively charged
surface and will flow into a  side chamber  and be attracted by a sta-
tionary electrode.  The anions are similarly attracted  into a  side
chamber on the opposite  side of the central chamber.   This process
jnay have application for the purification of a small side stream, but
more laboratory and development work will be required before the
technique becomes operational for use in  treating scrubber liquora
(Ref. 45).
                                  87

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 5.1.14        Electrodialysis
               Electro dialysis uses electric current to drive charged
 ions through one or more ion-permeable membranes.  The passage of
 current through the solution causes an increase in the concentration of
 one species on one side of the membrane and a corresponding reduc-
 tion on the other side.  It is necessary to ensure the feed water does
 not contain suspended particles or they will clog the pores of the mem-
 brane; therefore,  removal of suspended solids is accomplished by a
 separation pretreatment.  Tests, which were  conducted with sea water,
 have shown that a  potable water can be obtained.  However, further
 work is necessary to develop this concept before it can be considered
 fully operational for use with scrubber water (Refs. 46 through 48).
 5.1.15        Foam Separation
               A process has been tested in the  laboratory in which it
 is reported that sodium hydroxyphenyl butylbenzyl sulfonate as a sur-
 face active agent is mixed with water and then flowed countercurrent
 in a tower with nitrogen  gas with a pH of 5. 5 to  8 to remove Co,  Cr,
 and Ni from the water.   A subsequent separation operation is needed
 with this process  (Ref.  29).
 5.1.16         Solar Distillation
               Techniques  and equipment to utilize solar energy to sup-
ply heat to  evaporate water and subsequently condense the vapor as
pure water is being investigated. One solar still concept being tested
 is a large  covered pond which uses solar energy for heating and
evaporating the water in the pond.   The vaporized water condenses
on the underside of the pond roof and runs off through troughs to a
collection basin.   This technique shows promise for hot,  dry areas
such as the southwestern U.S., but it has obvious limitations in the
colder  climates and locations with many days of cloud cover.  With
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the current U.S.  energy shortage, more effort is being expended by
government agencies and private research laboratories to develop
practical concepts to harness solar energy.  However, additional
research and testing is still needed before a concept employing solar
energy is  considered usable for treating scrubber liquor in all areas
of the U.S. (Ref. 49)>
5. 1. 17        Analysis of Review
              An analysis of the numerous water treatment processes,
techniques, and equipment reveals that a lime-soda softening process
and a separation operation to remove the precipitates  will reduce the
concentration of As, B,  Ca,  Cd, Cr, Cu,  Fe, Hg,  Mg, Pb, Se, Zn,
and sulfates in the scrubber  liquors; however, the  process will not
reduce the concentration of certain soluble ingredients (i.e. , sodium
and chloride  salts).  This process is currently operational and will
not require a  breakthrough or advancement in the state of the art.
              In plants where brackish water is acceptable for service
water, the lime-soda softening would be adequate.  However,  in plants
where brackish water  is unacceptable,  an additional operation such as
reverse osmosis or ion exchange will be necessary.  A pH adjustment
may be required in some cases. An evaporation/condensation process
will also produce acceptable water.  Adaptations of this latter process
for treating scrubber liquor are the multistage flash evaporator and
the brine  concentrator techniques;  either would produce a condensate
capable of being  reused in the power plant or discharged.
               It is recommended that before a full-scale plant for
treating scrubber liquors is installed,  pilot plant testing be performed
on the specific scrubber liquor to be treated to acquire specific data
to properly size the equipment and to check out its operation.  This
study reviewed the literature and held  technical discussions
                                  89

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with power plant operators and organizations active in water
treatment processing and equipment manufacturing.  No work was
done in the laboratory to treat any of the scrubber liquors.
5.2            SELECTED WATER TREATMENT PROCESSES
               Processes adaptable for treating scrubber water to
reduce the concentration of ingredients were identified in Section 5.1.
As indicated,  many processes are available that could reduce the con-
centration of one or more of the constituents; however, their develop-
ment status ranges from, those still in laboratory testing to those that
are in full-scale operation (Refs. 13 through 49).  In reviewing the
different processes, five appear to have been developed to the  degree
that they can be considered an off-the-shelf process and readily adap-
table for use in treating the scrubber system bleed streams.  Table 5-2
lists these processes and their capability for meeting the water qual-
ity criteria.  Each of these is discussed in the  following Sections.
5.2.1          Liime^-Soda Softening Process
               The concept of using currently available processes to
treat scrubber liquors at the potential discharge point is fulfilled by
this process if the plant is designed to accept brackish water (defined
for this study  as water having 5000  mg/t or greater of chloride).  In
this process lime (CaO)  and soda ash (Na-CO,) are reacted with the
major species in the liquor to precipitate the Ca and Mg  together with
the heavy metals.  The pH is  adjusted with carbon dioxide and  the
solution is filtered or centrifuged with the. precipitates being sent to the
disposal site and the product water fed to the reverse osmosis or ion
exchange operation for chloride removal if the  power plant cannot
accept brackish water for service water.
                                90

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  Table 5-2.   CAPABILITY OF WATER TREATMENT PROCESSES
              TO MEET REQUIREMENTS
Water treatment
process (in
decreasing order of
cost effectiveness)
Lime -soda softening
Lime -soda softening
plus reverse
osmosis
Lime -soda softening
plus ion exchange
Multistage flash
evaporation
Brine concentration

Criteria
EPA- proposed
public water
supply intake --
October 1973
No
Yes

Yes
Yes
Yes

Nonpo table service water
Brackish
water
acceptable
Yes
Not
applicable

Not
applicable
Not
applicable
Not
applicable
Brackish
water not
acceptable
No
Yes

Yes
Yes
Yes

o
Brackish water for this study is defined as water having 5000 mg/ฃ
or more of chloride.
              The literature indicates that the lime-soda softening
process can reduce the concentration of the Ca and Mg salts to less
than 1000 mg/4.  Data showed that about an 80 to 90 percent reduction
in concentration of As, Cd,  Mn, Pb,  and Se has been achieved by this
process and, depending upon the source of the data analyzed,  it was
reported that 30 to 90 percent of hexavalent chromium can be removed.
Boron will also be reduced in concentration during the softening pro-
cess; insoluble calcium and magnesium borate salts are formed and
                                                               *
subsequently removed with other  precipitates.
                                 91

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              The pH of the liquor at the potential discharge points
ranges from 3 to 10.7 for the four scrubbing systems studied and ex-
ceeds the criteria of  5 to  10  (Table 2-1).  If the pH of the water is low
at the time of bleed to the water treatment plant, the pH will be in-
creased by adding lime.  After precipitation and prior to filtration or
centrifugation there is a pH adjustment with carbon dioxide, if neces-
sary, to  lower the pH.
5.2.2         Pretreatment Process (Lime-Soda Softening)
              Plus Reverse Osmosis
              The use of reverse osmosis  to treat the product water
from the lime-soda softening pretreatment  process will remove sodium
chloride  salts and other  undesirable constituents and will result in
a high-quality product readily capable of meeting both the service water
and the EPA-proposed public water supply intake criteria.
              The three basic designs for commercial reverse osmosis
modules  are as follows:
         a.    The tubular type that uses  small diameter (about 1/2-
              in.-diameter) porous or perforated tubes.  The reverse
              osmosis membrane is  installed on either the internal
              or external side of the tube and bundles of the tubes are
              joined  to a  feed water header system.
        b.    The hollow fiber type that uses many capilliary tubes
              in a bundle configuration.
        c.    The spiral  wound type  that uses a flat sheet of mem-
              brane to cover each side of a flat sheet of porous
              water-conducting material.  The membrane is sealed
              on the two long sides and one end to form an envelope.
              The other side of the membrane and porous water-
              conducting material is  sealed to a perforated tube that
              receives the product water.
                                 92

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All three types are designed to operate at pressures of about 30 to
45 kg/sq cm (430 to 640 psi) and are being used commercially.
              Reverse osmosis was initially developed to produce
potable water from brackish supplies, but because multivalent ions
such as Ca, Mg,  and  sulfate are as readily rejected as are the mono-
valent ions (e.g., Cl), this  concept has been adapted for boiler feed
water and treatment of waste waters for reuse.  The literature implies
that the reverse osmosis treatment would be the only operation needed
to treat the scrubber  water  for either  reuse or discharge.  However,
reverse osmosis equipment manufacturers and system users recom-
mended that because of the high concentration of the major species in
the scrubber water, a  lime-soda softening process should precede the
reverse osmosis operation.  The pretreatment would reduce the con-
centration of the  major species  to a level compatible with current
operational practices and experience, eliminate any objectional col-
loidal matter present in the scrubber liquor, and prevent precipitation
of large deposits of the Ca and Mg sulfate  salts on the membrane sur-
face.  Furthermore,  this high concentration would have a greater ten-
dency to cause an increase  in equipment downtime for cleaning and
repair and a predicted shorter membrane  life.  A higher reverse
omosis investment as well as higher operating costs could result than
if pretreatment were  used followed by reverse osmosis to remove the
final traces of  the cations and anions.
               The percent  water loss from the pretreatment and re-
verse osmosis system was  estimated  to be about 25 to 30 percent of
the feed water  to the  water  treatment  facility.   This water would con-
tain extremely high concentrations of the undesirable ingredients
 (e.g. , As, Hg, Pb, and Se) and should be disposed of with the waste
 products from the  scrubber.
                                 93

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 5.2.3         Pretreatment Process (Lime-Soda Softening)
               Plus Ion Exchange
               A review of the literature and technical discussions
 held with ion exchange manufacturers indicated that the use of the
 ion exchange process by itself •would not be an economical approach
 as a scrubber liquor water treatment process.  The manufacturers
 recommend that a pretreatment operation to reduce the high con-
 centration of constituents be undertaken before flowing the water over
 the ion exchange resins.  Otherwise,  there would be excessive equip-
 ment down time for flushing and  clean up of the resin beds.  However,
 by using a pretreatment consisting of lime-soda  softening and filtra-
 tion or centrifugation, the constituent concentration levels will be re-
 duced to values that can be handled by an ion exchange process to pro-
 duce a product capable of meeting the EPA-proposed public water sup-
 ply intake criteria.
               Numerous resins  of various chemical compositions are
 available or are being tested for  general water treatment and for spe-
 cific element removal.   These resins are, by definition, insoluble
 solids containing fixed cations and anions  capable of reversible ex-
 change with mobile ions  of the opposite sign in the solutions with which
they are brought into contact. Ion exchange was used for years in water
 softening and limited impurity removal; however, industry is now
developing newer resins for different applications.  For example,
Rohm and Haas  has developed a deionization process for use in desali-
nation work.  The process is based upon the use of weak electrolyte
ion exchange resins for treating brackish waters of 500 to 5000 ppm
total dissolved  solids.   The process consists of three units in series:
the alkalization unit, dealkalization unit, and carbonation unit.   The
influent to the first unit is passed through a bed of weak base anion
exchange resin in which the  anionic constituents are converted to the
                                 94

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bicarbonate salts of Na, Ca, and Mg.  In the second unit, which
contains a weak acid cation exchange resin, the bicarbonate salts are
converted to carbonic acid.  The third unit, which also contains a weak
base anion exchange resin but in the free base form,  absorbs the car-
bonic acid from the effluent of the second unit.  After the exhaustion
cycle is complete, the first unit is regenerated to the free base form
while the second unit is converted back to the hydrogen form.   Since
the third unit is already in the bicarbonate form,  the flow pattern is
simply reversed for the next cycle.  The third unit becomes the alka-
lization unit and the first unit becomes  the carbonation unit. An adap-
tation of this process could be used to remove the chlorides from the
scrubber liquor.
               Other ion exchange resin beds must also be  incorporated
into the overall process to remove specific trace metals that may be in
excessive  concentration.  Specific resins are  available for selective
heavy metal removal.   For example, Rohm and Haas1 Amberlite EX  318
resin is used to concentrate Cd, Co, Cu, Fe, Hg, Ni, Pb,  V,  and Zn,
and EX 243 is used to  remove B.  Other manufacturers market resins
also capable of removing trace  elements.
               There is a water loss incurred in conjunction with the
operation of an ion exchange process.  The amount is a function of  the
degree of backwashing  and rinsing during the regeneration  cycle and
can be determined precisely only by conducting pilot plant tests using
the exact liquor and with  the specific manufacturer's  resin.  However,
it is estimated that the degree of loss would be 25 to 30 percent of the
feed water to the treatment facility.
5.2.4         Multistage Flash Evaporation
               Multistage flash  evaporation involves the process of
progressively  heating and flash evaporating the scrubber liquor in a
series of stages under progressively lower pressures.  Each stage of
                                 95

-------
 the evaporator is configured with a heat exchanger for preheating the
 incoming liquid and a vacuum  chamber for flash evaporation.   The
 vapor is used for preheating the liquid and is condensed in this oper-
 ation.  The condensate or product water from each stage is collected
 for reuse in the power plant or discharged. A portion of the residual
 concentrated scrubber water is mixed with influent liquor for recycling
 through the evaporator; the  remaining portion is transported to a dis-
 posal area.  The product from this operation is of high quality and
 suitable for boiler feed water  or for drinking water as evidenced by
 the fact that this process has  been widely used as an  acceptable
 technique for producing potable water from sea water.
               There is a loss of water with the concentrated slurry
 mix.   The exact quantity of water lost is a function of the specific
 design of the evaporator and the equipment operating characteristics.
 For example, equipment that is operated to achieve a total dissolved
 solids (TDS) content in the discharge concentrate of 100,000 ppm,
 using a 10,000 ppm TDS feed water and <50 ppm TDS product con-
 densate, has a water loss of 10 to  12 percent of the water fed to the
 evaporator.

 5.2.5        Brine  Concentration
              A brine concentrator using  the concept of a falling film
 evaporator can produce a product that can meet the reuse or discharge
water quality criteria.  This type of concentrator flows the feed water
in a film inside a tube bundle,  and a portion of this film is vaporized.
A vapor compression thermodynamic cycle is part of the system in
which the vapor is compressed and introduced to the  shell side  of the
tube bundle.  The temperature  differential between the vapor  and the
water film causes the vapor  to  condense as pure wate.r. The  concen-
trated brine solution is subsequently withdrawn for disposal.  It is-
                                 96

-------
estimated that with a feed water of about 10,000 ppm total dissolved
solids,  a discharge concentrate of 100,000 ppm,  and a product of
< 50 ppm, there would be a loss of about 10 percent of the feed water.
5. 3           ESTIMATED WATER TREATMENT COSTS
              In order  to make a comparison of the economics of the
five selected water treatment processes discussed in Section  5.2,
engineering cost  estimates were prepared for each process.  Both
capital and operating costs were considered, and all costs were based
on  1974 dollars (Ref. 50 through 62).  The results of the cost estimates
are shown in Figures 5-1 through  5-5.  The capital  costs for  each
process were based on  average annual charges of 18 percent of the
original investment over a 30-year life including straight line deprecia-
tion,  parts replacement,  insurance, taxes, and cost of capital.  Opera-
ting costs were based on 4560 operating hours per year (30 year average)
and included labor,  maintenance,  repair, and operating power charges.
Two types of coal were assumed to be burned:
         a.     Type 1 coal has a thermal content of 29,700 joules/gm
               (12, 500  Btu/lb)  and is burned at the rate of 0. 38 kg
               (0. 84 Ib) of coal to  produce  1 kWh of electricity.
         b.     Type 2 coal has a thermal content of 18,600 joules/gm
               (8,000 Btu/lb) and is burned at the rate of 0.42 kg
               (0. 92 Ib) of coal per kWh produced.
               The capital and operating cost comparisons for water
treatment contained in  Sections 5. 3. 1 through 5. 3. 5 are based on a
flow rate variation of 200 to 700 gpm.
                                 97

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    •  PRETREATMENT PROCESS USED:  LIME-SODA SOFTENING
    •  1974 DOLLARS
    •  1000 MW POWER  PLANT SCRUBBER
    •  LAND COSTS NOT INCLUDED
    •  TO CONVERT gpm TO cu m/hr MULTIPLY BY 0.227

> ~ 2
Z
 BRINE
 CONCENTRATOR

 MULTISTAGE
 FLASH
 EVAPORATOR

PRETREATMENT
PLUS ION
EXCHANGE
PRETREATMENT
PLUS REVERSE
OSMOSIS
                                       LIME/ SODA
                                       SOFTENING
     '0               500               1000
      WATER TREATMENT PLANT CAPACITY, gpm
     Figure 5-1.  Estimated capital investment
                         98

-------
    • PRETREATMENT PROCESS USED: LIME-SODA SOFTENING
    • 1974 DOLLARS
    • 1000 MW POWER PLANT SCRUBBER
    • COSTS BASED ON 30-YEAR ANNUALIZED COSTS, 4560 OPERATING
      HOURS PER YEAR  AVERAGE  OVER 30 YEARS
  1.25
   1.0
  0.75
O
at
m
o.
LJ
O
go. so
  0.25
                             TO CONVERT
                                FROM
   TO
MULTIPLY
   BY
                             gpm
                             gal
          i   ii   i
 cu
 liter
  0.227
  3.785
MULTISTAGE FLASH
EVAPORATOR OR BRINE
CONCENTRATOR

PRETREATMENT PLUS
ION EXCHANGE

PRETREATMENT PLUS
REVERSE OSMOSIS
                                         LIME-SODA SOFTENING
      0               500               1000

      WATER TREATMENT PLANT CAPACITY, gpm
 Figure 5-2.  Estimated water treatment costs per gallon
                             99

-------
       • PRETREATMENT PROCESS USED: LIME-SODA SOFTENING
       • 1974 DOLLARS
       • 1000 MW POWER PLANT SCRUBBER
       • COSTS BASED ON 30-YEAR ANNUALIZED COSTS, 4560 OPERATING
        HOURS PER YEAR,  AVERAGE OVER 30 YEARS
       0.5
    2 0.
    Q
    O
    Of
    Q.
    Of.
    Ul
    Q.
      0.3
      0.2
      0.1
TO CONVERT
   FROM
                        TO
MULTIPLY
   BY
           gpm
                      cu m/hr
            i    i   i    i
              I
                     0,227
MULTISTAGE
FLASH EVAPORATOR
OR BRINE
CONCENTRATOR
                                 PRETREATMENT
                                 PLUS ION EXCHANGE
                                 PRETREATMENT
                                 PLUS REVERSE
                                 OSMOSIS
                                LIME-SODA
                                SOFTENING
                                    i   i    I
         0               500              1000

          WATER TREATMENT PLANT CAPACITY, gpm
Figure  5-3.  Estimated water treatment costs per kilowatt hour
             for power output of 1000 MW
                               100

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  10
Q.
Z
UJ

2
CD

1
at
in
a.
i
iii
o
 •  PRETREATMENT PROCESS USED:  LIME-SODA SOFTENING
 •  1974 DOLLARS
 •  1000 MW POWER PLANT SCRUBBER
 •  COAL:  TYPE No.  1 — 12,500 Bty/lb, 0.84 Ib/kWh

         TYPE No.  2 — 8,000 BtM/lb, 0.92 Ib/kWh

 •  COSTS BASED ON 30-YEAR ANNUALIZED COSTS,  4560 OPERATING
   HOURS PER YEAR  AVERAGE  OVER 30 YEARS
      TO CONVERT
         FROM
                TO
MULTIPLY
   BY
   gpm       cu m/hr      0.227
   BtiVlb      joules/gm     2.235
   Ib/kWh     kg/kWh      0.4536
'^/Million Btu  ml 11 s/M joule  0.00948
    0               500              1000
    WATER TREATMENT PLANT CAPACITY,  gpm
      COAL TYPE No. 1
           BRINE CONCENTRATOR OR MULTISTAGE FLASH EVAPORATOR
           PRETREATMENT PLUS  ION EXCHANGE
           PRETREATMENT PLUS  REVERSE OSMOSIS
      COAL TYPE No. 2
      G33E3 BRINE CONCENTRATOR OR MULTISTAGE FLASH EVAPORATOR
            PRETREATMENT PLUS ION EXCHANGE
            PRETREATMENT PLUS REVERSE OSMOSIS
      CZZZZ3 LIME-SODA SOFTENING
 Figure 5-4.
         Estimated water treatment costs per million
         Btu heat input for  power output of 1000 MW
                              101

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    •  PRETREATMENT PROCESS USED: LIME-SODA SOFTENING
    •  1974 DOLLARS
    •  1000 MW POWER PLANT SCRUBBER
    •  COAL: TYPE  No.  1 — 12,500 Btu/lb,   0.84 Ib/kWh

           TYPE  No.  2 — 8,000 Btu/lb, 0.92b/kWh

    •  COSTS BASED ON  30-YEAR ANNUALIZED COSTS, 4560 OPERATING
      HOURS PER YEAR AVERAGE OVER 30 YEARS
Q
hi
OL
CO
_i
O
u
O
Of.
O
Of.
Ill
a.
8
u
 1.0
0.75
  0.50
0.25
                                        TO CONVERT
                                           FROM
                        TO
MULTIPLY
   BY
           gpm        cu m/hr      0.227
           Btu/lb       joules/gm     2.235
           Ib/kWh      kg/kWh       0.4536
           $/short ton   $/metric ton   1.105
       I
I   I    I
      0               500               1000
      WATER TREATMENT PLANT CAPACITY,  gpm

       COAL TYPE No. 1
            BRINE CONCENTRATOR OR MULTISTAGE FLASH EVAPORATOR
            PRETREATMENT PLUS ION EXCHANGE
            PRETREATMENT PLUS REVERSE OSMOSIS
            LIME-SODA SOFTENING
            TYPE NO. 2
            BRINE CONCENTRATOR OR MULTISTAGE FLASH EVAPORATOR
            PRETREATMENT PLUS ION EXCHANGE
            PRETREATMENT PLUS REVERSE OSMOSIS
       I/////I LIME-SODA SOFTENING
       Figure 5-5.
                   Estimated water treatment costs per ton of
                   coal burned for power output of 1000 MW
                                   102

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5.3.1         Lime-Soda Softening

              Capital investment charges vary from $0.47M to
$0.9M, and total average treatment costs over 30 years,  including
annualized capital charges and operating costs, vary from 0.51 cents

per gallon to  0.25 cents per gallon over the same range.   These

costs convert to the following:

        a.    From 0.053 to 0.092 mills per kWh produced.  The
              power was assumed  to  be produced at an average
              annual rate of 4560 million kWh.
        b.    From 0.0047 to 0.0081 mills per megajoule (0.51 to
              0. 88 centers  per million Btu) heat input from Type  1
              coal and from 0.0067 to 0.0116 mills per megajoule
              (0. 73 to 1.26 cents per million Btu) heat input for
              Type 2 coal.

        c.    From 0. 14 to 0.24 dollars per metric ton (0. 13 to
              0.22 dollars  per short ton) of coal burned for Type  1
              coal and 0. 13 to 0. 22 dollars per metric ton (0. 12 to
              0.20 dollars  per short ton) of coal burned to Type 2
              coal.

5.3.2         Lime-Soda Pretreatment Plus Reverse Osmosis

              The capital investment varies from 3/4 to  2 million

dollars.  Athough currently used membranes have a service life of

about 3 years  (depending upon the specific operating conditions and

quality of the feed water), industry sources are predicting a membrane
life of 5 to 6 years for membranes  now being evaluated; therefore,
membrane life was  assumed to be 5 years.  Labor  expenses were

assumed to  be $200,000  per year.

              The average  water treatment costs for the  lime-soda

softening pretreatment plus reverse osmosis over a 30-year period.

range from 0.90 to  0. 51  cents per  galloon.  These costs convert to:

        a.    From 0. 11 to 0.22 mills per kWh produced.  Power
              was assumed to be produced at an average annual
              rate  of 4560 million kWh.
                               103

-------
         b.     From 0.011 to 0.019 mills per megajoule (1.2 to 2.0
               cents per million Btu) heat input for Type 1 coal and
               from 0.014 to 0.027 mills per meagjoule (1.5 to 2.9
               cents per million Btu) heat input for Type 2 coal.
               (See Section 5. 3 for a definition of Type 1 and 2 coals.)

         c.     From 0. 31 to 0. 57 dollars per metric ton (0. 28 to
               0. 52 dollars per short ton) of coal burned for Type  1
               coal and 0.28 to 0.53 dollars per metric ton (0.25 to
               0.48 dollars per short ton) of coal burned for Type  2
               coal.

5.3.3          Lime-Soda Softening Plus  Ion Exchange

               The initial investment ranges from $1. 1 to 2. 5 million.

The resin life was estimated to be 5 years.  The estimated average

water treatment costs over a period of 30 years for the flow rate

range assumed above are as follows:

         a.     From 1. 1 to 0.62 cents per gallon of water treated.

         b.     From 0. 14 to 0.27  mills per kWh produced.  Power
              was assumed to be  produced at a constant average
               annual rate of 4560 million kWh.
         c.     From 0.011 to 0.023 mills per megajoule (1.2 to 2. 5
               cents per million Btu) heat input for Type 1 coal and
              from 0.019 to 0.034 mills per megajoule (2.0 to 3. 6
               cents per million Btu) for  Type  2 coal.  (See  Sec-
               tion 5.2.2.2 for a definition of Type 1 and 2 coals.)

         d.     From 0. 39 to 0. 67  dollars per metric ton (0. 35 to
              0.61 dollars per short ton) of coal burned for Type  1
               coal and 0. 35 to 0.  63 dollars per metric ton (0. 32 to
              0. 57 dollars per short ton) of coal burned for Type  2
               coal.

               These costs are about 20 to 30 percent higher than the

pretreatment process plus reverse osmosis operation that will provide

water of comparable quality.

              In reviewing the quality of the water produced and the

investment and treatment costs, it appears as  if the lower cost pre-

treatment and reverse osmosis  operation is a more cost-effective
                                104

-------
approach than pretreatment and an ion exchange operation to provide
water of sufficient quality for reuse or discharge.
5.3.4         Multistage Flash Evaporator
              The estimated investment for a multistage flash evap-
oration facility ranges from about $1.4 to  3.7 million (Figure 5-1).
These  values are 60 to 90 percent more than for comparable quality
water obtained from the pretreatment process plus a reverse osmosis
operation,  and the average water treatment costs are estimated to
be 1-1/4 to 1-2/3 times higher (Figures 5-2  through 5-5).
              Consequently, it does not appear to be cost effective
to use  a multistage flash evaporator to treat scrubber water when the
lime-soda  softening and  reverse osmosis process will provide the
quality of water needed at a lower cost.
5.3.5         Brine Concentrator
              Brine concentrators have been operational only a rela-
tively  short time compared to other available water treatment pro-
cesses. The  estimated initial  investment  and water treatment costs
are compared to the other processes in Figures 5-1 to 5-5.  The
economic analysis was made on the  same basis as previously described,
except that the labor was reduced to only a part-time operator on the
recommendation of the manufacturer, thus,  the labor was  estimated
at $50,000 per year.  It is expected that in the  future the brine con-
centrator costs can be reduced.  However, at the present time  this
process is technically compatible with the requirement to produce a
product with reduced concentrations of ingredients to meet the water
quality criteria, but it does not appear to  be as cost effective to em-
ploy this process for low cost, off-the-shelf water treatment for
scrubber liquor when other processes such as lime-soda softening
and reverse osmosis could accomplish the same function at a lower
cost.
                                 105

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                         REFERENCES
1.    Jones, J. W.,  et al.  Disposal of By Products from Non-
     Regenerable Flue Gas Desulfurization Systems.  (Presented
     at American Society of Civil Engineers Annual and National
     Environmental Engineering Convention.  Kansas  City, Missouri.
     October  21-25,  1973.)

2.    Rossoff, J., et al.  Disposal of By-Products from Non-
     Regenerable Flue Gas Desulfurization Systems - a Status
     Report.  (Presented at the EPA Control Systems Laboratory
     Symposium on Flue Gas Desulfurization.  Atlanta, Georgia.
     November 4-7,  1974.)

3.    Rossoff, J., and R. C. Rossi.  Disposal  of By-Products from
     Non-Regenerable Flue Gas Desulfurization Systems: Initial
     Report.  Environmental Protection Agency.  Publication
     Number  EPA 650/2-74-037-a.   May  1974.

4.    Federal  Water Pollution Control Act Amendments of 1972 -
     92nd Congress-Second Session.  United States Code
     Congressional and Administrative News,  Number 10.  West
     Publishing Company.  1972.

5.    Public Health Service Drinking Water Standards  1962.  U.S.
     Public Health Service.  Publication Number 956.  1962.

6.    Water Quality Criteria.  Report of the National Technical
     Advisory Committee  to the Secretary of the Interior.
     April 1968.

7.    McKee,  J.  D.,  and H. W. Wolf. Water Quality  Criteria.
     Publication Number 3-A.  State Water Resources Control
     Board, California.  April 1971.

8.    Proposed Criteria for Water Quality. Environmental
     Protection Agency.  October 1973.
                                107

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 9.   Steam Electric Power Plant Generating Point-Source Category,
      Effluent Guidelines and Standards.  Federal Register.  39,
      Number 196:  October 8, 1974.

10.   Personal Communication with TVA and Bechtel Corporation
      personnel associated with the EPA/TVA Shawnee Steam Plant
      Flue Gas Desulfurization Scrubbing Test Project.  TVA
      personnel:  P. Stone,  K. Metcalfe, and J.  Barkely; Bechtel
      personnel:  L. Sybert and S. Almaula.  Subject: Operations
      of EPA/TVA Shawnee Steam Power Plant.

11.   Personal communication.  P.  L.  Baldwin and N. J. Ozenberger,
      Arizona Public Service Company,  Cholla Station, Joseph City,
      Arizona. Subject: Operations of Cholla Station.

12.   Personal communication.  S. L. Pernick and R. D.  O'Hara,
      Duquesne Light Company, Phillips Station, South Heights,
      Pennsylvania. Subject:  Operations of Phillips Station.

13.   Perry, J. H. , Editor.   Chemical Engineering Handbook.
      New York,  McGraw-Hill Book Company.

14.   Brine Concentrator Specification RCC  225T.  Resources
      Conservation  Company.  Bulletin.  1974.

15.   Personal communication.  O. Kirchner, Resources Conservation
      Company, Renton, Washington.  Subject:  Brine concentrator
      designs and applications.

16.   Eckenfelder,  W. W.,  and L.  K. Cecil, Editors.  Progress in
      Water Technology Applications  of New Concepts of Physical -
      Chemical Waste Water Treatment.  Nashville,  Tennessee,
      International Association on Water Pollution Research and
      American Institute of Chemical Engineers.  September 1972.

17.   Cecil, L. K.,  Editor.  Complete Water Reuse.  American
      Institute of Chemical Engineers, National Conference on
      Water Reuse.  April 1973.

18.   Personal communication.  T. E. Bird, Western Sales Manager,
      The Bird Company,  South Walpole, Massachusetts.  Subject:
      Centrifugation and filtration equipment.

19.   Personal communication.  E. H. Dewey, Field Engineer,
      Hoffman Air and Filtration Division, Clarkson Industries,
      Syracuse, New York.  Subject:  Filtration clarification and
      vacuum distillation equipment.
                                108

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20.  Personal communication.  C. Novotny,  Technical Director,
     Industrial Filter and Pump Manufacturing Company,  Eicero,
     Illinois.  Subject:  Removal of suspended solids.

21.  Cruver, J.  E., and I. Nusbaum.  Application of Reverse
     Osmosis to Wastewater  Treatment.  Journal of Water Pollution
     Control Federation.  46: 2, 1974.

22.  Fan, L. T., et al.  Analysis of a Reverse Osmosis Water
     Purification System and its Optimization Based on the Plug
     Flow Model for the Bulk Flow in a Membrane Unit.  Institute
     for Systems Design and  Optimization, Kansas State University,
     Manhattan,  Kansas.  1969.

23.  Personal communication.  W. McCorvalle,  Technical
     Representative,  Monsanto Company, St. Louis, Missouri.
     Subject:  Hollow fibers for use in membrane separation processes.

24.  Personal communication.  C. Miller, Applications Engineer,
     Polymetrics Division of Technical Equities  Corporation,  Santa
     Clara, California.  Subject:  Costs and  operations of reverse
     osmosis water treatment process.

25.  Lepper,  F.  R.   Reverse Osmosis: Larger  Plants and Wider
     Use.  Power Engineering.  May 1973.

26.  Personal communication,  L. Winer, Regional Manager,
     Barnstead Company Division of Sybron  Corporation, Los
     Angeles, California.  Subject:  Reverse osmosis and ion
     exchange processes.

27.  Bresler, S. A., and E. F. Miller.  Economics of Ion Exchange
     Techniques for Municipal  Water Quality Improvement.  Journal
     of American Water Works Association.   64; 11,  1972.

28.  Trace Metals in Water Supplies:  Occurrence,  Significance and
     Control. Proceedings of the 16th Water Quality Conference.
     American Water Works Association, Illinois Environmental
     Protection  Agency, and University of Illinois.  February 1974.

29.  Cadman, T. W., and R. W.  Dellinger.   Techniques for Removing
     Metals from Process Wastewater. Chemical Engineering.
     April 15, 1974.

30.  Giusti,  O.  M. ,  et al.  Activated  Carbon Absorption of
     Petrochemicals.  Journal Water  Pollution Control Federation.
     46:  5,  1974.
                                 109

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31.   Wyman, G. D.  Remove Organics from Feedwater Make Up.
      Power.  July 1972.

32.   Personal communication.   B.  B. Berger, Director of Water
      Resources Research Center, University of Massachusetts.
      Subject: Wastewater treatment processes.

33.   Personal communication.   D.  G. Argo, Assistant District
      Engineer,  Orange County Water District, County of Orange,
      Santa Ana,  California. Subject:  Reclamation and reuse of
      county wastewater.

34.   Wesner, G.  M.  Water Factory 21 and Waste Water Reclamation
      and Sea Water Barrier Facilities. Orange County Water District,
      Santa Ana,  California. February 1973.

35.   Wesner, G.  M. ,  and D. G. Argo. Report on Pilot Waste Water
      Reclamation Study. Orange County Water District, Santa Ana,
      California.  July  1973.

36.   Personal communication.   W. Zabban,  Chief Engineer,  The
      Chester Engineers, Coraopolis, Pennsylvania.  Subject:
      Wastewater treatment processes.

37.   Betz Handbook of Industrial Water Conditioning.  Betz
      Laboratories, Trevose, Pennsylvania.   1973.

38.   James, G.  V.  Water Treatment.  International Scientific
      Series.  Edinburgh, Scotland, T and A.  Constable, Ltd.

39.   Personal communication.   A.  Poole,  Director of Water and
      Waste Utilities, Springbrook Water Reclamation Center,
      Naperville, Illinois.   Subject:  Reclamation and reuse of
      city wastewaters.

40.   Personnal communication.  J.  S. Kneale, The Permutit
      Company,  Paramus, New Jersey. Subject:  Water treatment
      processes.

41.   Personal communication.   R.  Carrillo,  Sales Representative,
      Zimmite Corporation, Thousand Oaks,  California.  Subject:
      Water treatment chemicals.

42.   Wing,  R. E.  Heavy Metal Removal from Waatewater with Starch
      Xanthate.  Northern Regional  Research Laboratory,  U.S. •
      Department of Agriculture, Peoria,  Illinois.  March 1974.
                                110

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43.   Personal communication.  D. W.  Miller, Assistant Director,
      U.S. Department of Agriculture, Agricultural Research Service,
      Northern Regional Research Laboratory, Peoria, Illinois.
      Subject:  Heavy metal removal from wastewaters.

44.   Laboratory Demonstration of the Atomics International Process
      for Removal of Heavy Metals from Water.  Publication
      Number 47.  California State Water Resources Control Board
      Report AI-73-13.

45.   Benner, P. E.  U.S. Patents,  448,  026.  Removal of Ions from
      an Ionized Liquid.  June 3,  1969.

46.   Christodoulou,  A. P.,  et al.  Parametric Economic and
      Engineering Evaluation Study of the Electrodialysis Process for
      Water Desalination.  U.S. Department of Interior.  1969.

47.   Bennett,  G.  F., Editor.  Water -  1972.  American Institute of
      Chemical Engineers Symposium Series Number  129.  69; 1973.

48.   Bennett,  G.  F., Editor.  Water -  1973.  American Institute of
      Chemical Engineers Symposium Series Number  136.  70; 1974.

49.   Androsky, A.  Uses of the Sun in the Service of  Man.  The
      Aerospace Corporation, El Segundo, California.  Publication
      Number ATR-74(9970)-1.  October 1973.

50.   Blecker, H. G., et al.  How to Estimate and Escalate Costs of
      Wastewater  Equipment.  Chemical Engineering, Deskbook Issue.
      October 21,  1974.

51.   Personal communication.  J. L. Willa, Vice-President of Sales,
      Lilie-Hoffman Cooling Towers, Inc., St. Louis, Missouri.
      Subject:  Cooling tower operations, costs, blowdown, and losses.

52.   Boies, D. B.,  et al.  Technical and Economic Evaluations of
      Cooling Systems Blowdown Control Techniques.  Environmental
      Protection Agency.  Publication Number EPA 660/2-73 -026.
      November 1973.

53.   Porter, K. S. , and A. G. Boon.   Cost of Treatment of Waste
      Water.  Symposium on Trent Research Programs. Water
      Pollution Research Laboratory of the Department  of the
      Environment,  University of Nottingham, England.  1971.
                                Ill

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54.   Farrow,  J.  C. ,  et al.  Estimating Construction Costs of Waste
      Water Treatment Systems.  Journal of American Association of
      Textile Chemists and Colorists.  2:  3, February 1970.

55.   Hinomoto, H.  Unit and Total Costs  - Functions for Water
      Treatment Based on Koenig's Data.  Water Resources Research.
      7:  5,  1971.

56.   Ackerman, W. C.  Cost of Water Treatment in Illinois. Technical
      Letter Number 11.  Illinois State Water Survey.  1968.

57.   DiGregorio, D.  Cost of Wastewater Treatment Processes.
      Dorr-Oliver Inc.

58.   Prehn, W. L. , et al.  Desalting Cost Calculating Procedures.
      U.S. Department of Interior Research and Development.
      Publication Number 555.  May  1970.

59.   Eckenfelder, W. W., and D.  L. Ford.  Economics of Wastewater
      Treatment.  Chemical  Engineering.  August 25, 1969.

60.   Smith, R. Cost of Conventional and Advanced Treatment of
      Wastewater.  Journal of Water  Pollution Control Federation.
      40:  9, 1968.

61.   Personal communication.   R. Cookingham, Sales Representative,
      Gregory Pump Company, Alhambra, California.  Subject:  Costs
      for  slurry pumps.

62.   Eckenfelder, W. W., and J.  L. Barnard.  Treatment - Cost
      Relationship for Industrial Wastes.   Chemical Engineering
      Progress.  67_: 9,  1971.

63.   Handbook for Analytical Quality Control in Water and Wastewater
      Laboratories.  Analytical Quality Control Laboratory, National
      Environmental Research Center,  Cincinnati,  Ohio.  1972.

64.   Methods for  Chemical Analysis of Water and Wastes.  Analytical
      Quality Control Laboratory, National Environmental Research
      Center,  Cincinnati, Ohio.  1971.
                                112

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                           APPENDIX A
       DESCRIPTION OF CHEMICAL ANALYSIS TECHNIQUES

A.I           INTRODUCTION
              This appendix describes the analytical techniques (Refs.
63 and 64) used to determine the concentration of constituents  in the
scrubber liquors.  The constituents are divided into  (a) major chem-
ical species (calcium, sodium, sulfate,  and chloride),  (b)  trace metal
species, and (c) additional chemical species.  Other water quality
tests are also described.
              Consideration was given to the constituent's range of
concentration and to the corresponding costs of the analyses to obtain
                                           *r
data having high precision or high accuracy.   Although the basis for
selecting the proper analytical technique was minimizing any inter-
ference from other species, the presence of chemical  species inter-
fering with a particular analysis was fully acknowledged.  Only when
the interference was  considered significant were corrections applied.
A. 2          MAJOR CHEMICAL SPECIES
A. 2. 1        Calcium Determination
               The method selected from among several has an accu-
racy of 4 percent and was one in which calcium oxalate was precipitated
  Precision is defined as the relationship between a measured value and
the statistical mean of measured values, and accuracy is the relation-
ship between the true value and the measured value.
                                  113

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 and filtered from the solution,  the filter cake was redissolved in HC1,
 and the solution was titrated against KMnO, to a characteristic purple
 end point.  Correction was then made for excess permanganate at the
 characteristic end point.
               Alternative techniques using a  specific ion electrode and
 atomic absorption spectrophotometry were eliminated because they had
 lower accuracies resulting from interferences, primarily from the
 sulfate ions.
 A. 2. 2         Sodium  Determination
               Atomic  absorption spectrophotometry was selected in
 preference to a method that determines sodium gravimetrically by
 separating the calcium salts from the sodium salts in the scrubber
 liquors by fractional precipitation.  The selected technique uses a
 Perkin-Elmer 303 instrument with a graphite furnace at  3302A wave-
 length. For every test the liquor concentration required multiple dilu-
 tions to achieve a level suitable for optimum analytical determination.
 Any errors in  results tend to be high because of the effects of interfer-
 ence and the high concentration of sodium in the scrubber liquors; how-
 ever,  the errors are less than  10 percent.
 A. 2. 3         Sulfate Determination
               Standard nephelometry techniques are used for this task.
A barium sulfate precipitate was formed by the reaction of the sulfate
ion with a barium chloranilate reagent.  The resulting turbidity was
determined by a spectrophotometer and compared to a curve from stan-
dard sulfate solutions.   Although multiple dilutions are necessary to
bring the concentration to a range of optimum reliability,  the resulting
error is less than 10 percent.
                                  114

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A.2.4        Chloride Determination
              A solid-state electrode was used to determine the
electrode potential of chloride ions in scrubber liquors.  The results
were compared against a standard curve.  This method has a precision
of about  1 percent and an accuracy greater than 5 percent.
A. 3           TRACE METAL SPECIES
              Since most trace metal species are highly sensitive to
atomic absorption spectrophotometry, this technique was used.  A
Perkin-Elmer 303 instrument, with deuterium background corrector,
and a graphite tube heater, for increased sensitivity, were used to
determine soluble concentrations for the following elements:  alumi-
num, antimony, boron, beryllium, cadmium, chromium, copper,  co-
balt,  iron, magnesium, manganese,  molybdenum,  nickel, lead, silicon,
silver,  tin, vanadium,  and zinc.  Precision and accuracy are dependent
upon the specific element,  its relative concentration, and the extent of
interference. The precision and accuracy of the measurements of con-
centrations of all  elements that exceed water quality reuse criteria
ranged between 5  and 20 percent.
              Mercury was also determined using this technique; how-
ever, the mercury is  reduced to the elemental state with stannous chlo-
ride and the absorption produced from the resulting mercury vapor is
measured.   This method has  a  precision of about 20 percent and an
accuracy probably greater than 50 percent.
               Arsenic was determined by the  Gutzeit method that re-
acts  arsine with mercurous bromide to produce Hg-As; the unknown is
compared colorimetrically against standards.  For this application this
technique has a precision of about 25 percent and an accuracy probably
greater than 50 percent.
               A fluorimetric technique that has a sensitivity down to
micrograms per liter was used to determine selenium.  It has a preci-
 sion of about 10 percent and is  accurate to 100 percent.
                                  115

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 A. 4           ADDITIONAL CHEMICAL SPECIES
               If these species existed in sufficiently high concentration,
 they would affect the water quality of the liquors; however,  most of
 them were present in trace quantity and their importance in defining
 water quality was considered insignificant.  Therefore,  precise or
 complete analyses were not considered of particular value to this pro-
 gram.  The concentration of many of them is controlled  by  interaction
 with one or more of the major species. Their expected  concentration
 was determined using an Aerospace Corporation developed  computer
 program (part of the work for a related EPA contract) that  calculates
 the maximum concentration of each minor species in chemical equi-
 librium with the major species in the  system.  The experimental deter-
 minations were always in agreement with the expected concentration
 value a.
 A.4.1         Carbonate Determination
               Total carbonate was determined gravimetrically by the
absorption of CO., evolved from an acidified sample.  This technique
does not have high sensitivity and could not detect concentrations  in
scrubber liquors at values less than  10 mg/t carbonate.  (The expected
value determined by the Aerospace computer program was typically
less than 1 mg/i for all samples analyzed.)
A.4. 2         Sulfite Determination
               Total sulfite was determined using a specific ion elec-
trode and no significant interferences were observed.  The oxidation of
the sulfite ion to sulfate in the scrubber liquor was found to be a very
rapid reaction.  Liquor protected from the atmosphere will typically
reveal concentrations of several hundred milligrams per liter of the
sulfite ion; however, a  brief atmospheric exposure will cause oxidation
                                                               *
and reduce these concentrations by one or more orders of magnitude.
                                  116

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The reported sulfite measurements were for samples analyzed
immediately upon arrival in the laboratory.  No specific action was
taken to inhibit oxidation other than to ensure that the samples were
transported from the power plant scrubber to the analytical laboratory
in sealed containers.  The exposure to air during sampling, filtering,
and measuring,  however, resulted in the sulfite values reported.  It is
presumed that these concentrations would probably more closely repre-
sent the oxidation state of liquor in the event of their potential discharge.
A.4. 3        Phosphate Determination
              The  phosphate analysis was determined by spectrophoto-
metry methods, using ammonium molybdate to form the molybdenum
blue complex.  Total range of phosphate  content varied  from 0. 5 mg/S.
in an  acid liquor (pH = 4.3) to 0.01 mg/i in a base liquor (pH =  10.4).
A.4.4        Nitrogen Determination
              Total nitrogen was determined by the Kjeldahl method
which converts organic nitrogen components to ammonia.  The ammo-
nia is then distilled and the amount determined by titration.  This
method has a precision of about 10 percent,  and accuracy at the levels
of the concentrations determined is about 25 percent.
A.4. 5        Fluoride Determination
              The fluoride ion was determined by the specific ion
electrode using a Beckman Model 76 digital pH meter.   There are no
significant interferences in the scrubber liquors.  This method has a
precision of about  5 percent; an accuracy of 20 percent is attainable at
the low levels measured.
                                 117

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 A. 5           OTHER WATER QUALITY TESTS
 A. 5. 1         Chemical Oxygen Demand
               Chemical oxygen demand was determined by reacting
 the organics and sulfites  present with potassium dichromate and mea-
 suring the reduced chromium by spectrophotometry.  While a precision
 of 25 percent is attainable, accuracy depends on the sample history
 (i.e. , degree of exposure to atmospheric oxygen) and is about  100 per-
 cent for routine analysis.
 A. 5. 2         Total Alkalinity
               Total alkalinity is determined by titrating a 25 mt sam-
 ple with standard acid to a pH of 4. 0.   The Beckman Model 76  digital
 pH meter is used as the indicating instrument.   Total alkalinity is ex-
 pressed as milligrams per liter calcium carbonate, but is actually a
 determination of the buffering capacity of the liquor due to a number of
 weak acid species (i.e., carbonate, sulfite, borate, arsenite,  selenite,
 and silicate).   Precision is about  5 percent and accuracy is estimated
 to be 25 percent.
 A. 5. 3         Total Dissolved Solids Determination
               The total dissolved solids are determined gravimetri-
 cally by evaporating a 10 to 25 ml sample overnight in a tared weighing
bottle under vacuum at 120ฐF.   Since two of the  major constituents
 (calcium and sodium sulfates) form stable hydrated salts and are very
hygroscopic in the anhydrous state, prolonged drying and minimal ex-
posure of the dried residue are mandatory.  The precision is about 2
percent, and the accuracy is about 5 percent.
A. 5.4        Total Conductance  Determination
              This measurement, which was made with a General
Radio Impedance Bridge Type 1650A, gives an estimate of the total
                                 118

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ionic strength of the liquor.  Precision is about 1 percent, and accuracy
is estimated to be about 2 percent.
A.5.5         pH  Determination
              This parameter is measured with a Beckman Model 76
digital pH meter to a precision of 0.2 percent and an accuracy of 1
percent.
A.5. 6         Turbidity Determination
              Turbidity measurements were made by nephelometry in
which light absorption is compared to standards that were prepared
using a formazin mixture that is a mixture of hydrazine sulfate and
hexamethylene tetramine in a water solution.  Most scrubber liquor
samples were obtained as  slurries and were  virtually opaque.  Chem-
ical analyses were performed on filtered samples, and turbidity values
were also obtained on these filtered samples. Only a few samples were
obtained as filtrate; their results are reported as received rather than
after filtering.
                                 119

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                           APPENDIX B
                   COSTING BACKGROUND DATA

B. 1           INTRODUCTION
              This appendix describes the methodologies used in
preparing the cost estimates for the various water treatment processes
analyzed in this  study.  The rationale used for both capital and oper-
ating costs is presented.
B.2           CAPITAL AND OPERATING  COSTS
              The cost data obtained from the various sources listed
in the reference section were converted,  in all cases, to equivalent
1974 dollars.  This conversion was made by use of an appropriate eco-
nomic indicator  such as the Plant Cost Index published monthly in
Chemical Engineering.  The estimated capital and operating costs for
each water treatment process are included with the description of each
process and are based on treating 200 to  1000 gpm.   Total annualized
costs were compiled as the total of annualized capital costs and oper-
ating costs.
B. 2.1         Capital Cost Estimates
              The  capital costs for the various water treatment pro-
cesses were based  on an equipment operational life of 30 years.  The
annualized capital charges were estimated on this basis  and include
elements  such as insurance, cost of capital, depreciation,  replace-
                                                               •
ments, and taxes.  Certain specific equipment items, such as reverse
                                 121

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 osmosis membranes,  identified as having a service life less than 30
 years were depreciated on an accelerated schedule, e.g. ,  five years.
 The itemized approach for computing annualized capital charges is
 shown in Table B-l.  It should be noted that the cost of land was not
 included in the capital cost estimates.
              The estimated capital costs  for various water treatment
 processes can be illustrated by the approach used on lime-soda ash
 softening.  From data obtained from the references, installed costs
 were generated for the clarifier-reactant tank, the chemical storage
 hopper and feed system, the filter,  two surge  tanks, five pumps (plus
 five spares),  piping for the complete facility,  and building  and site
 improvements.  The pumps and piping  were assumed  to be fabricated
 with stainless steel because  of the corrosive nature of the water being
 handled.  These costs were derived as a function of flow rate.  An
 additional  10 percent was added for  interest expense during construc-
 tion.  The average annualized capital charges  were computed on the
 total of these  amounts at the rate  of 18 percent,  as described in Table
 B-l.  This same procedure was used in arriving at the capital cost
 estimates for the other water treatment processes.
 B. 2. 2        Operating Cost Estimates
              The operating cost estimates were computed on the
basis of 4560 hours per year (190 days) as an average over 30 years.
Again, using the lime-soda treatment as an example,  the chemical
costs, utility power, materials, operating labor, and maintenance
labor were computed as a function of flow rate.  An overhead rate of
20 percent was applied  to the total of these  costs.  As stated above,
annualized capital and operating costs were combined to obtain total
annual costs.
                                 122

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    Table B-l.  AVERAGE ANNUALIZED CAPITAL CHARGES
               (30-YEAR LIFE - 1974 DOLLARS)

              Straight line depreciation  is assumed
              Cost elements
  Percentage of
capital investment
Depreciation based on 30-year life

Replacements  items:  20% of depreciation

Insurance
                                               Subtotal
           3.33

           0.67

           0.50

           4.50
Cost of capital:
Taxes
        50% debtฎ 11%
        11% (0.5)

        50% equity @15%
        15% (0.5)
        Assume Federal tax to be the
        same as equity

        Other taxes at 80% of Federal
        tax
           5.50


           7.50
           7.50

           6.00

Subtotal   26.50
On a 30 year basis, the average annual
capital charge on initial investment is
                 = 17.75%
Total
17..7 5
                               123

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 B. 3           WATER TREATMENT COST CURVES
               The cost curves presented in Section 5.2 of this report
 were based on the operation of a scrubber at a 1000 MW station.  The
 cost parameters are plotted as a function of flow rate for  each of the
 five processes considered to be readily adaptable to treating scrubber
 bleed water.
 B. 3. 1         Capital Investment
               The data plotted in the curves shown in Figure  5-1 re-
 present the costs for materials and labor to install the water treatment
 processing equipment,  including  contractors' fees, engineering design,
 construction supervision, and interest expenses during construction at
 a  rate of 8 percent annually.  These curves  do not include land costs,
 start-up costs,  or brine disposal.  The cost estimates were prepared
 by contacting manufacturers, the treatment  industry,  and  government
 experts, as well as  conducting a  thorough literature search.
 B.3.2        Treatment Costs per Gallon
              The estimated water treatment costs per gallon (Figure
 5-2) were prepared  for each process by combining the annual capital
 and operating costs  as a function of the total annual flow rate.   The
 annualized capital charges were calculated as described in Section
 B. 2. 1.  The annual operating costs were estimated as described in
 Section B. 2. 2.
 B.3.3         Treatment Costs per Kilowatt Hour
              The process  treatment costs per kilowatt hour (Figure
 5-3) were computed from the total annual costs consisting  of annualized
capital charges as described in Section B. 2. 1, plus annual operating
costs,  for 4560 operating hours per year.  The average annual energy
                                  9
output was  assumed to be 4. 56 x  10  kWh.
                                 124

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B.3.4         Treatment Costs per Million BTU
              Heat Input
              Water treatment costs as a function of Btu input (Figure
5-4) were computed from the total annual costs for each treatment
process and the weight and Btu content of the two types of coal con-
sidered.   The coal quantities computed were based on a 1000 MW out-
put and 4560 average operating hours per year.
B.3.5         Water Treatment Costs per Ton of Coal
              The total annual costs for each water treatment process
were computed as a function of weight of coal burned.  Consideration
was given to the characteristics of type 1  and  2 coal for a 1000 MW
station.  The same  average annual operating period of 4560 hours was
used for  this calculation as for the other operating curves.
                                 125

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                                 TECHNICAL REPORT DATA
                          (Please read Instructions on the reverse before completing)
 1. REPORT NO.
   EPA-600/2-76-024
                            2.
                                                       3. RECIPIENT'S ACCESSION NO.
 4. TITLE ANDSUBTITLE
 Reuse of Power Plant Desu Ifurization Waste Water
                                   5. REPORT DATE
                                    February 1976
                                                       6. PERFORMING ORGANIZATION CODE
 7 AUTHOR(S)L.J.Bornstein, R.B. Fling, F.D.Hess,
 R. C. Rossi, and J. Rossoff
                                                      8. PERFORMING ORGANIZATION REPORT NO.
 9. PERFORMING ORflANIZATION NAME AND ADDRESS
 The Aerospace Corporation
 2350 East El Segundo Boulevard
 El Segundo, California 90245
                                   10. PROGRAM ELEMENT NO.
                                   1BB392: ROAP R21AZU-025
                                   11. CONTRACT/GRANT NO.
                                   Grant R-802853-01-0
 12. SPONSORING AGENCY NAME AND ADDRESS
 EPA, Office of Research and Development
 Industrial Environmental Research Laboratory
 Research Triangle Park, NC 27711
                                   13. TYPE OF REPORT ANC
                                   Final; 1/74-4/75
                                                                     NO PERIOD COVERED
                                   14. SPONSORING AGENCY CODE
 15 SUPPLEMENTARYNOTESFOI. technical details contact Fred Roberts, EPA, Environmental
 Research Laboratory, 200 SW 35th St. , Corvallis, Oregon 97330
 16. ABSTRACT The repOrf giV6s results of an assessment of the potential reuse of liquor
 from nonregenerable flue gas desulfurization systems by applying available water
 treatment processes.  Although scrubbers normally operate in a closed-loop mode,
 this study investigated liquor reuse if a scrubber purge became necessary as a
 result of off-design or other operating conditions.  Chemical characterizations were
 performed on liquors from four different scrubbers; these were assessed for use as
 power plant service water or for direct discharge.  Treatment is required for either
 use; but, in most cases (for  economic reasons), treatment for  discharge is not
 recommended.  Chemical precipitation (e.g. , lime-soda softening, filtration, and
 pH control) is adequate for most service water usage  cases.  Cases involving high
 chloride content in the purge liquor would require an additional treatment such as
 reverse osmosis, as would all cases for direct discharge.  The applicabilities  of
 available treatment systems  are given, in addition to scrubber flow diagrams,  water
 balance, and treatment costs for a range of liquor flow rates.
                             KEY WORDS AND DOCUMENT ANALYSIS
                DESCRIPTORS
 Air Pollution
 Waste Water
 Liquids
 Regeneration
    (Engineering)
 Reclamation
Water Treatment
Electric Power  Plants
Flue Gases
Desulfurization
Scrubbers
Chemical Analysis
                                          b.IDENTIFIERS/OPEN ENDED TERMS
Air Pollution Control
Stationary Sources
Reuse
                                               c. COSATI Field/Group
13B
       10B
       21B
       07A
 3. DISTRIBUTION STATEMENT
                                          19. SECURITY CLASS (This Report)
                                          Unclassified
                                                                   21. NO. OF PAGES
                                                   136
 Unlimited
                       20. SECURITY CLASS (Thispage)
                       Unclassified
                                                                   22. PRICE
EPA Form 2220-1 (9-73)
                  126

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