United States
Environmental Protection
Agency
                                        821-R-08-011
         Steam Electric Power Generating
                    Point Source Category:
         2007/2008 Detailed Study Report
                U.S. Environmental Protection Agency
                            Engineering and Analysis Division
                                       Office of Water
                             1200 Pennsylvania Avenue, NW
                                 Washington, D.C. 20460
                                        August 2008

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2007/2008 Detailed Study Report                                                       Contents


                                     CONTENTS

                                                                                 Page


1.      INTRODUCTION AND BACKGROUND OF THE STUDY	1-1

2.      DATA COLLECTION ACTIVITIES	2-1
       2.1    Facility Inspections	2-1
       2.2    Wastewater Sampling	2-6
       2.3    Data Request	2-8
       2.4    Interactions with UWAG	2-11
             2.4.1   Database of Power Plant Information	2-12
             2.4.2   Wastewater Sampling	2-12
             2.4.3   Data Request	2-12
             2.4.4   NPDESForm2C	2-12
       2.5    Interactions with EPRI	2-13
       2.6    Department of Energy (DOE)	2-14
             2.6.1   FormEIA-860	2-14
             2.6.2   FormEIA-767	2-14

3.      OVERVIEW OF THE COAL-FIRED STEAM ELECTRIC INDUSTRY	3-1
       3.1    Flue Gas Desulfurization Systems	3-1
             3.1.1   Process Description and Wastewater Generation	3-2
             3.1.2   Coal-Fired FGD System Statistics	3-7
             3.1.3   FGD Wastewater Characteristics	3-17
             3.1.4   FGD Wastewater Treatment	3-30
       3.2    Ash Handling Operations	3-46
             3.2.1   Process Description and Wastewater Generation	3-46
             3.2.2   Ash Sluice Water Characteristics	3-47
             3.2.3   Ash Sluice Treatment Systems	3-59
       3.3    Coal Piles	3-61
             3.3.1   Coal Pile Runoff Generation	3-61
             3.3.2   Coal Pile Runoff Characteristics	3-61
             3.3.3   Coal Pile Runoff Treatment Systems	3-62

4.      REFERENCES	4-1

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2007/2008 Detailed Study Report                                                  List of Tables


                                 LIST OF TABLES

                                                                                Page

2-1    Summary of 2007/2008 Detailed Study Site Visits	2-4

2-2    Summary of 2007/2008 Detailed Study Sampling Program	2-6

2-3    Analytes Included in 2007/2008 Detailed Study Sampling Program	2-7

2-4    Profile of Coal-Fired Power Plants Operated by Data Request Respondents	2-9

3-1    Scrubbed Coal-Fired Steam Electric Power Generation as of June 2008	3-9

3-2    Scrubbed Capacity of EPA's Data Collection Sources	3-11

3-3    Characteristics of Coal-Fired Power Plants with Wet Scrubbers	3-12

3-4    Projected Future Use of FGD Systems at Coal-Fired Power Plants	3-15

3-5    FGD Scrubber Purge Flow Rates	3-18

3-6    Influent to FGD Wastewater Treatment System Concentrations	3-21

3-7    Effluent from FGD Wastewater Treatment Systems Concentration	3-26

3-8    FGD Wastewater Treatment Systems Identified During EPA's Detailed Study	3-31

3-9    Fly Ash Sluice Flow Rates	3-48

3-10   Bottom Ash Sluice Flow Rates from EPA Data Request Responses	3-49

3-11   Ash Pond Influent Concentrations	3-50

3-12   Ash Pond Effluent Concentrations	3-55

3-13   Fly Ash Handling Practices at Plants Included in EPA's Combined Data Set	3-60

3-14   Fly Ash Sluice Wastewater Treatment Systems at Plants Included in EPA's
       Combined Data Set	3-60

3-15   Coal Pile Runoff Generation from EPA Data Request Responses	3-61
                                          11

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2007/2008 Detailed Study Report                                                  List of Figures


                                 LIST OF FIGURES

                                                                                 Page

2-1    Geographic Distribution of Coal-fired Power Plants Included in EPA Data Collection
       Activities for 2007/2008 Detailed Study	2-1

2-2    Geographic Distribution of Coal-fired Power Plants Included in EPA's Site Visit and
       Sampling Program for the 2007/2008 Detailed Study	2-3

2-3    Geographic Distribution of Coal-fired Power Plants for which Data Request
       Respondents Provided Technical Information	2-10

3-1    Process Flow Diagram for a Limestone Forced Oxidation FGD Scrubber System	3-5

3-2    Process Flow Diagram for a Lime or Limestone Non-Forced Oxidation FGD
       Scrubber	3-8

3-3    Wet Scrubbed Generating Capacity, 1977-2025	3-14

3-4    Wet Scrubbed Capacity as a Percentage of the Total Coal-Fired Generating Capacity,
       1977-2025	3-14

3-5    Coal-Fired Power Plants Operating Wet FGD Scrubber Systems, as of June 2008	3-16

3-6    Coal-Fired Power Plants Projected to be Operating Wet FGD Systems in 2020	3-17

3-7    FGD Scrubber Purge Flow Rate Distributions from EPA Data Request Responses,
       Site Visits, and Sampling	3-19

3-8    FGD Scrubber Purge Normalized Flow Rate Distributions from EPA Data Request
       Responses, Site Visits, and Sampling	3-19

3-9    Process Flow Diagram for a Hydroxide and Sulfide Chemical Precipitation System... 3-37
                                          in

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2007/2008 Detailed Study Report
List of Acronyms
                                LIST OF ACRONYMS

BODs        Biochemical oxygen demand (5-day)
CAIR        Clean Air Interstate Rule
CAMR       Clean Air Mercury Rule
CBI         Confidential Business Information
CFR         Code of Federal Regulations
CWA        Clean Water Act
CWTS       Constructed wetland treatment system
DBA        Dibasic acid (a mixture of glutaric, succinic, and adipic acid)
DCN        Document control number
DOE        Department of Energy
DPY        Days per year
ELGs        Effluent limitations guidelines and standards
EIA         Energy Information Administration
EPA         Environmental Protection Agency
EPRI        Electric Power Research Institute
ESP         Electrostatic precipitator
FGD        Flue gas desulfurization
GPD        Gallons per day
GPM        Gallons per minute
GPY        Gallons per year
HEM        Hexane extractable material
IGCC        Integrated Gasification Combined Cycle
IPM         Integrated Planning Model
MW         Megawatt
NEEDS      National Electric Energy  Data System
NESCAUM  Northeast States for Coordinated Air Use Management
NETL        National Energy Technology Laboratory
NOx         Nitrogen oxides
NPDES      National Pollutant Discharge Elimination System
O&M        Operation and maintenance
PCS         Permit Compliance System
QC          Quality control
SBR         Sequencing batch reactor
SCR         Selective catalytic reduction
SGT-HEM   Silica gel treated-hexane  extractable material
SNCR        Selective non-catalytic reduction
SO2         Sulfur dioxide
TDS         Total dissolved solids
TKN        Total Kjeldahl nitrogen
TMT        Trimercapto-s-triazine
TRI         Toxics Release Inventory
TSS         Total suspended solids
UWAG      Utility Water Act Group
ZLD         Zero liquid discharge
                                          IV

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2007/2008 Detailed Study Report                     Chapter 1 - Introduction and Background of the Study
 1.     INTRODUCTION AND BACKGROUND OF THE STUDY

       The Steam Electric Power Generating effluent limitations guidelines and standards
 (ELGs) (40 CFR 423) apply to a subset of the electric power industry, namely those facilities
 "primarily engaged in the generation of electricity for distribution and sale which results
 primarily from a process utilizing fossil-type fuel (coal, oil, or gas) or nuclear fuel in conjunction
 with a thermal cycle employing the steam water system as the thermodynamic medium."  (40
 CFR 423.10) EPA's most recent revisions to the ELGs for this category were promulgated in
 1982 (see November 19, 1982; 47 FR 52290).  Section 304(m) of the Clean Water Act (CWA)
 requires EPA to develop and publish a biennial plan that establishes a schedule for the annual
 review and revision of national ELGs required by Section 304(b). EPA last published an
 Effluent Guidelines Program Plan in 2006 [71 FR 76644; December 21, 2006].

       For the 2008 Effluent Guidelines Program Plan, EPA conducted a detailed study of the
 steam  electric power generating industry to determine if the ELGs should be revised. This
 document describes the activities EPA undertook during the detailed study (referred to
 hereinafter as the "2007/2008 detailed study").

       EPA has focused efforts for the 2007/2008 detailed study on certain discharges from
 coal-fired steam electric power plants (referred to hereinafter as  "coal-fired power plants").
 Specifically, the study has focused on: (1) characterizing the mass and concentrations of
 pollutants in wastewater discharges from coal-fired power plants; and (2) identifying the
 pollutants that comprise a significant portion of the category's toxic-weighted pound equivalent
 discharge estimate and the corresponding industrial processes responsible for the release of these
 pollutants. EPA's previous  annual reviews have identified that the toxic-weighted loadings for
 this category are predominantly driven by the metals present in wastewater discharges, and that
 the waste streams contributing the majority of these metals are associated with ash handling and
 wet flue gas desulfurization (FGD)  systems. Other potential sources of metals include coal pile
 runoff, metal/chemical cleaning wastes, coal washing, and certain low volume wastes.

       The 2007/2008 detailed study was a continuation of a detailed study initiated to support
 the 2006 Effluent Guidelines Program Plan (i.e., the "2005/2006 detailed study"). In the
 2005/2006 detailed study, EPA initially investigated whether pollutant discharges reported to the
 Permit Compliance System (PCS) and Toxics Release Inventory (TRI) for 2002 were accurate in
 reflecting that the Steam Electric Power Generating Point Source Category (40 CFR Part 423)
 discharges relatively high amounts of toxic-weighted pollutants, in comparison to other industry
 sectors. EPA also performed an in-depth analysis of the reported pollutant discharges and
 reviewed technology innovation and process changes. Additionally, EPA evaluated certain
 electric power and steam generating activities that are similar to the processes regulated for the
 Steam Electric Power Generating Point Source Category, but that are not currently subject to
 ELGs. For more information on the 2005/2006 detailed study, see Interim Detailed Study Report
for the Steam Electric Power Generating Point Source Category (EPA-821-R-06-015;
 November 2006) [U.S. EPA, 2006ab].

       During the 2005/2006 detailed study, EPA identified data gaps and issues that may affect
 the Agency's estimate of the potential hazards caused by discharges from steam electric facilities.
 To fill these gaps, EPA is currently collecting information on the wastewater characteristics and
 treatment technologies used at facilities in the Steam Electric Point Source Category. To date,

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2007/2008 Detailed Study Report                     Chapter 1 - Introduction and Background of the Study
EPA has collected data for the 2007/2008 detailed study through facility inspections, wastewater
sampling, a data request that was sent to a limited number of companies, and various secondary
data sources (see Chapter 2 for more detail on these data sources).

       EPA's Office of Water is coordinating its efforts for the study with ongoing research and
activities being undertaken by other EPA offices, including the Office of Research and
Development, the Office of Solid Waste, and the Office of Air and Radiation (Office of Air
Quality Planning and Standards and the Office of Atmospheric Programs). EPA is also
coordinating certain activities with the Utility Water Act Group (UWAG), an industry trade
association, and has held technical information discussions with the Electric Power Research
Institute (EPRI) and treatment equipment vendors.

       This report, Steam Electric Power Generating Point Source Category: 2007/2008
Detailed Study Report (EPA-821-R-08-011; DCN05516), describes the status of EPA's detailed
study of the steam electric industry as of June 2008. It documents the data and information that
EPA used to support decisions with respect to the study and the 2008 Effluent Guidelines
Program Plan.

       EPA is continuing to assess available information on facilities that are not currently
regulated under Part 423 but that use a steam cycle to generate electricity.  EPA is also
continuing to evaluate pollution prevention and water reuse opportunities in the industry;
additional data that have recently been submitted by industry for review; additional questions on
electric power generators using non-fossil and non-nuclear fuel; and other emerging issues such
as use of Integrated Gasification Combined Cycle (IGCC) technology.

       Based on the information compiled to date for the steam electric industry, EPA has
determined that further review of the analytical data recently collected and the collection of
additional wastewater treatment and cost data is warranted.

       This report is organized into the following chapters:

       •      Chapter 2 discusses the data sources used in the 2007/2008 detailed study;

       •      Chapter 3 presents a profile of coal-fired power plants, with a focus on those
              operations using wet FGD systems; and

       •      Chapter 4 presents the references cited in this report.
                                           1-2

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2007/2008 Detailed Study Report                                 Chapter 2 - Data Collection Activities
2.     DATA COLLECTION ACTIVITIES

       As described in Chapter 1, EPA is focusing efforts for the 2007/2008 detailed study on
certain discharges from coal-fired power plants, including FGD system wastes and ash handling
wastes.  EPA is collecting data through facility inspections, wastewater sampling, a limited
survey of selected facilities, and various secondary data sources. Figure 2-1 shows the locations
of coal-fired power plants at which EPA has conducted site visits, collected samples of
wastewater, or obtained technical information via the data request.



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  Figure 2-1.  Geographic Distribution of Coal-fired Power Plants Included in EPA Data
                    Collection Activities for 2007/2008 Detailed Study

2.1     Facility Inspections

       EPA is  currently conducting a site visit program to gather information on the types of
wastewaters generated by coal-fired power plants, as well as the methods of managing these
wastewaters to allow for recycle, reuse, or discharge.  For the 2007/2008 detailed study, EPA has
focused data gathering activities primarily on FGD wastewater treatment and management of ash
sluice water.

       In early 2007, EPA compiled a list of 96 U.S. coal-fired power plants believed to operate
wet FGD systems, based on information received from EPA's Office of Air and Radiation (Hall,
2007a). EPA subsequently received and reviewed data from the Utility Water Act Group

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2007/2008 Detailed Study Report                                   Chapter 2 - Data Collection Activities


(UWAG), an industry trade association, on 76 plants (75 of the plants operate wet FGD
scrubbers), which includes two additional plants not previously identified by EPA [ERG, 2008f].
The data provided by UWAG included information on air pollution controls in place, process
configurations, and other characteristics of the plants (see Section 3.2 for more information).
The compiled facility data for the 75 plants operating wet FGD scrubbers are believed to
represent approximately 65  percent of the total population of coal-fired power plants currently
operating or planning to operate wet FGD  systems. *  EPA used the UWAG data in conjunction
with information from other sources, including publicly available plant-specific information and
contacts with state and regional permitting authorities, to identify potential candidate plants for
site visits.  EPA considered the following characteristics to select plants for site visits (not listed
in any priority order):

       •      Coal-fired boilers;

       •      Wet FGD system, including:
              —    Type of scrubber,
              —    Sorbent used,
              —    Year operation began,
              —    Chemical additives used,
              —    Forced oxidation process,
              —    Water cycling, and
              —    Solids removal process;

       •      Type of coal;

       •      Selective Catalytic Reduction (SCR) and/or Selective Non-Catalytic Reduction
              (SNCR) NOx controls;

       •      Ash handling systems;

       •      FGD wastewater treatment  system;

       •      Ash treatment system; and

       •      Advanced mercury air controls.

       Using these characteristics, EPA identified plants to contact and obtain more detailed
information about the plants' operations. From the information obtained during these contacts,
EPA selected 16 plants for site visits.  Plant conditions, such as type of FGD system and whether
target waste streams are  segregated or commingled with other wastes, influenced the plant
selection process. Figure 2-2 shows the geographic distribution of the plants that were visited.
1 As discussed in Section 3.1.2, EPA has identified 116 plants currently operating (or planning to operate) one or
more wet FGD systems from all of EPA's data collection activities. See the memorandum in the docket entitled
"Development of Version One of the Power Plant FGD System Data Set", dated 07/29/2008 (DCN 06128) for
details on the development of this list. The total number of plants operating wet FGD systems is dynamic; additional
plants have started operating FGD systems since UWAG provided information, or are currently in the process of
installing FGD systems. Therefore, the data provided by UWAG are believed to represent about 65 percent of the
total population of coal-fired plants currently operating wet FGD systems.	
                                             2-2

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2007/2008 Detailed Study Report                                   Chapter 2 - Data Collection Activities
                                       o
                                        a
                                                         ฐ  *


    Legend

     D  Plants that were visited by EPA and are not currently scheduled to be sampled
        Plants that have been or are scheduled to be sampled during EPA's detailed study
        (EPA conducted pre-sampling srte visits at each of these plants)
  Figure 2-2. Geographic Distribution of Coal-fired Power Plants Included in EPA's Site
               Visit and Sampling Program for the 2007/2008 Detailed Study

       During the site visits, EPA collected information on plant operations and types of
wastewater management techniques.  See Table 2-1 for information on the characteristics of
plants visited prior to June 2008.  EPA also used these visits to assess whether the site was
appropriate for sampling. The objectives of these site visits were to:

       •      Gather general information about the plant's operations;
       •      Gather process-specific information;
       •      Gather information on pollution prevention and wastewater treatment/operations;
       •      Gather plant-specific information to develop sampling plans; and
       •      Select and evaluate potential sampling points.

       From these visits, EPA selected six facilities as candidates for wastewater sampling
episodes prior to December 2008. Because most of the site visits conducted thus far have
focused on identifying plants for wastewater sampling, most of the site visits have been to plants
with more advanced FGD wastewater treatment systems. EPA is continuing to identify potential
site visit candidates to assess FGD systems using different scrubber designs or sorbents, such as
magnesium-lime, and facilities operating or planning  to install different types of treatment and
water reuse options, including facilities achieving zero liquid discharge from their wet FGD
system operations.

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2007/2008 Detailed Study Report
Chapter 2 - Data Collection Activities
                                  Table 2-1. Summary of 2007/2008 Detailed Study Site Visits
Plant Name
(Reference)
Yates
(ERG, 2007d)
Wansley
(ERG, 2007e)
Widows Creek
(ERG, 2007g; ERG,
2007J)
Conemaugh
(ERG, 2007k)
Homer City
(ERG, 2007h; ERG,
2007i)
Pleasant Prairie
(ERG, 2007c)
Bailly
(Hall, 2007b)
Seminole
(Jordan, 2007)
Big Bend
(ERG, 2007a; ERG,
2007f)
Cayuga
(Jordan, 2008b)
Mitchell
(ERG, 2007m)
Coal Type
Eastern Bituminous
Eastern Bituminous
Eastern Bituminous
Eastern Bituminous
Eastern Bituminous
Subbituminous (Powder
River Basin)
Bituminous (75%), Eastern
Bituminous (25%)
Eastern Bituminous, also
bums petroleum coke as a
small percentage (up to
30%)
Eastern Bituminous, also
bums petroleum coke as a
small percentage (typically
1-2%; 5% maximum)
Eastern Bituminous
Eastern Bituminous
FGD System
Chiyoda jet-bubbling reactor,
limestone forced oxidation, no
additives (1 unit)
Currently being installed
Spray tower, limestone forced
oxidation a, no additives (2 units)
Spray tower, limestone forced
oxidation, dibasic acid additive
(2 units)
Spray tower, limestone forced
oxidation, formic acid additive
(1 unit)
Spray tower, limestone forced
oxidation, no additives (2 units)
Spray tower, limestone forced
oxidation, no additives (2 units)
Spray tower, limestone forced
oxidation, dibasic acid additive
(2 units)
Two scrubbers for 4 units (2
units per scrubber): (1) spray
tower, limestone forced
oxidation, and (2) double loop
spray tower, limestone forced
oxidation, dibasic acid additive
Spray tower, limestone forced
oxidation, formic acid additive
(2 units)
Spray tower, limestone forced
oxidation, no additives (2 units)
Year FGD
Began
Operation
1992
NA
1977 and
1981
1994 and
1995
2001
2006 and
2007
1992
1984
1985 (double
loop) and
2000 (spray
tower)
1995
NA
SCR/SNCR
NOx Control
No SCR or
SNCR
SCRs on 2 units
SCRs on both
units with FGD
No SCR or
SNCR
SCRs on 3 units
SCRs on both
units with FGD
SCR on one of
the units with
FGD
No SCR or
SNCR
SCR on one unit.
Will install
SCRs on the
other units over
the next three
years.
SCR on 1 unit
SCRs on both
units with FGD
Type of FGD Wastewater Treatment
System
Settling pond
Currently installing a settling pond
Settling pond
Chemical precipitation (lime addition to
pH 8.6, ferric chloride, sodium sulfide,
polymer), followed by aerobic
sequencing batch reactors
Chemical precipitation (lime addition to
pH 8.1, ferric chloride, polymer),
followed by aerobic biological reactor
Chemical precipitation (lime addition to
pH 8.9, organo sulfide, ferric chloride,
polymer)
Polymer addition only; no pH adjustment
Chemical precipitation (lime addition to
pH 8, ferrous chloride, polymer)
Chemical precipitation (lime addition to
pH 9.0, ferric chloride, polymer)
Chemical precipitation (lime addition to
pH 10.7, ferric chloride, polymer)
Chemical precipitation (lime addition to
pH 8.5, ferric chloride, polymer)
Fly Ash
Handling
(wet/dry)
Wet
Wet
Wet
Dry
Dry
Dry
Dry
Dry
Dry
Dry
Wet

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2007/2008 Detailed Study Report
Chapter 2 - Data Collection Activities
                                        Table 2-1.  Summary of 2007/2008 Detailed Study Site Visits
Plant Name
(Reference)
Cardinal
(ERG, 2007n)
Bruce Mansfield
(U.S. EPA, 2008b)
Roxboro
(Jordan, 2008a)
Belews Creek
(ERG, 2008g)
Marshall
(ERG, 2008h)
Coal Type
Subbituminous
Bituminous
Eastern Bituminous
Eastern Bituminous
Eastern Bituminous,
additionally bums a small
percentage of South
American coal (2%)
FGD System
Currently being installed.
Venturi scrubber, magnesium-
enhanced lime, inhibited
oxidation (2 units). Horizontal
spray scrubber, magnesium-
enhanced lime, inhibited
oxidation (1 unit). Additional
forced oxidation as separate
process for all 3 units.
Tray tower, limestone forced
oxidation, no additive (2 units
operating, 2 more units planned
for 2008)
Spray tower, limestone forced
oxidation (1 unit operating, 1
more unit planned for 2008)
Spray tower, limestone forced
oxidation. (3 scrubbers for 4
units)
Year FGD
Began
Operation
NA
1976, 1977,
and 1980
2007 (and
planned for
2008)
2008
2006 and
2007
SCR/SNCR
NOx Control
SCRs on 3 units
SCRs on 3 units
SCRs on 4 units
SCRs on 2 units
SNCRson4
units
Type of FGD Wastewater Treatment
System
Currently being installed
Surface impoundment (settling)
Settling pond followed by a
anaerobic/anoxic biological treatment
system for removal of metals and
nutrients
Chemical precipitation followed by
anaerobic/anoxic biological treatment for
removal of metals and nutrients followed
by a constructed wetland treatment
system
Clarifier followed by a constructed
wetland treatment system
Fly Ash
Handling
(wet/dry)
Wet
Wet
Dry (but wet
capability)
Dry (but wet
capability)
Dry (but wet
capability)
a - The FGD system is a once-through system in which the gypsum slurry in the scrubber reaction tank is not recycled back through the scrubber, but rather, is continuously
discharged.
NA - Not available.
Note: The table reflects the data collected at the time of each individual site visit and does not reflect changes that have occurred since the site visits were conducted.

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2007/2008 Detailed Study Report
Chapter 2 - Data Collection Activities
2.2    Wastewater Sampling

       EPA is currently conducting a sampling program to characterize raw wastewaters
generated by coal-fired power plants, as well as evaluate treatment technologies and best
management practices used to reduce pollutant discharges. EPA developed a "generic" sampling
plan [ERG, 2007b; ERG, 20071] to provide general sampling procedures and methods EPA and
its contractors will follow when conducting sampling activities. This document, in combination
with plant-specific sampling plans, serves as a guide to the field sampling crew and provides
procedural information for plant personnel.

       EPA is in the process of collecting and analyzing samples to characterize wastewater
streams generated at six coal-fired power plants. EPA conducted wastewater sampling activities
at five of the plants between July and October 2007. Specifically, EPA is characterizing
wastewater streams associated with wet FGD systems and ash handling operations, and
evaluating the capability of various types of treatment systems to  remove metals and other
pollutants of concern prior to discharge.  See Table 2-2 for information on the plants selected as
part of the sampling  program and Figure 2-2 for the geographic distribution of coal-fired power
plants that were sampled or are planned to be sampled prior to December 2008.

           Table 2-2. Summary of 2007/2008 Detailed Study Sampling Program
Site
Big Bend
Homer City
Widows
Creek
Mitchell
Cardinal
TBD
Episode
No.
6547
6548
6549
6550
6551
TBD
Date of Sample
Episode
July 2007
August 2007
September 2007
October 2007
October 2007
Scheduled for
Fall 2008
Samples Planned for Collection
FGD
Influent
•/
•/
^
•/

^
In-Process

•/

•/

^
Effluent
•/
•/
^
•/

^
Ash Pond
Influent


•/
(fly + bottom)

•/
(fly ash)

Effluent

•/
(bottom ash)
•/
(fly + bottom)
•/
(fly ash + other)
•/
(fly ash)

       The steam electric sampling and analysis program thus far has consisted of one- to two-
day sampling episodes at selected plants. EPA is conducting the sampling activities primarily to
characterize the FGD and ash handling wastewaters and the performance of the systems used to
treat these wastes. For the five sampling episodes that EPA has already completed, EPA
prepared sampling episode reports, which discuss the specific sample points, the sample
collection  methods used, the field quality control (QC) samples collected, and the analytical
results from the wastewater samples.  The reports for these five episodes are in the docket for the
2008 Effluent Guidelines Program Plan [ERG, 2008J; ERG, 2008k; ERG, 20081; ERG, 2008m;
ERG, 2008n].
       Table 2-3 lists the analytes for which EPA has collected sampling data. The analytes
listed reflect the current understanding of coal-fired power plant wastewaters, including

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2007/2008 Detailed Study Report
Chapter 2 - Data Collection Activities
contributions from coal, scrubber sorbents, treatment chemicals, and other sources. In some
cases, the analytical method used (e.g., EPA Method 200.7) provides results for a range of
parameters and includes certain analytes that perhaps would not have been selected individually.

       Table 2-3. Analytes Included in 2007/2008 Detailed Study Sampling Program
Parameter
Method Number
Classical*
Biochemical Oxygen Demand (5-day) (BOD5)
Total Suspended Solids (TSS)
Total Dissolved Solids (TDS)
Sulfate
Chloride
Ammonia as Nitrogen
Nitrate/Nitrite as Nitrogen a
Total Kjeldahl Nitrogen (TKN)
Total phosphorus
Hexane Extractable Material (HEM)
Silica Gel Treated Hexane Extractable Material (SGT-HEM)
SM5210B
SM 2540 D
SM 2540 C
ASTMD516-90
SM 4500-C1-C
SM 4500— NH3 F (18th ed.)
SM 4500-NO3 H
SM 4500— N, C
EPA 365.3 (Rev 1978)
EPA 1664A
EPA 1664A
Metals
Total metals (27 metals: aluminum, antimony, arsenic, barium, beryllium, boron,
cadmium, calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese,
mercury, molybdenum, nickel, selenium, silver, sodium, thallium, tin, titanium,
vanadium, yttrium, and zinc)
Dissolved metals (27 metals)
Low-level total metals (11 metals: antimony, arsenic cadmium, chromium, copper,
lead, nickel, selenium, silver, thallium, zinc)
Low-level dissolved metals (11 metals)
Low-level total mercury
Low-level dissolved mercury
Hexavalent chromium
Low-level hexavalent chromium
EPA 200.7, 245.1,245.5
EPA 200.7, 245.1
EPA 1638
EPA 1638
EPA 163 IE
EPA 163 IE
ASTMD 1687-92
EPA 1636
a - EPA method 353.2 was used for the Nitrate/Nitrite as Nitrogen analysis for Sampling Episode 6548. Standard
Method 4500-NO3 H was used for Sampling Episodes 6549, 6550, and 6551. Nitrate/Nitrite as Nitrogen was not
analyzed for Sampling Episode 6547.

       EPA's sampling program is also collecting data on the design, operation, and
performance of treatment systems at steam electric plants, specifically regarding system design
and day-to-day operation. The sampling activities are focusing on influent, effluent, and in-
process streams for FGD and ash handling wastewater treatment systems. During each sampling
episode, EPA collects engineering information regarding the design and operation of the plant
being sampled (e.g., coal usage, plant capacity, wastewater flow rates, sludge generation rates,
and retention times in wastewater treatment process stages).  Engineering data collection sheets
were completed for each plant. This information is used to evaluate whether the specific design
or operational criteria of the steam electric operations affect the wastewater characteristics.
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2007/2008 Detailed Study Report                                 Chapter 2 - Data Collection Activities


       EPA will use data from the sampling program to support the following study objectives:

       •      Determine the pollutants present in wastewater streams generated by or associated
              with air pollution controls (e.g., wet FGD systems, SCR/SNCRNOx controls, wet
              ash handling systems);

       •      Characterize the performance of steam electric wastewater treatment systems; and

       •      Characterize the pollutants ultimately discharged to surface water from steam
              electric plants.

2.3    Data Request

       EPA collected information about coal-fired power plants by means of the Data Request
for the Steam Electric Power Generating Industry ("data request"), issued under authority of
Section 308 of the Clean Water Act [U.S.  EPA, 2007].  The data request complements EPA's
wastewater sampling effort by obtaining information about wastewater generation rates and
management practices for the FGD and ash sluice waste streams, other waste streams not
sampled by EPA's sampling program (e.g., coal pile runoff), and other power plant information
as described below.

       EPA selected nine power companies to receive the  data request based on  specific
characteristics of plants they operate.  Each of the companies selected operate coal-fired plants
that have wet FGD systems and/or wet fly ash handling systems.  Table 2-4 presents a profile of
the coal-fired power plants operated by the nine selected companies (referred to hereinafter as
"data request respondents"). As shown in Table 2-4, the data request respondents operate a total
of 67 coal-fired power plants and provided technical information for 30 of these coal-fired power
plants as instructed by Part B of the data request. These 30 coal-fired power plants (referred to
hereinafter as "data request plants") either operate wet FGD systems and/or are planning to begin
constructing wet FGD systems by December 31, 2010.  The plants that are most likely to operate
FGD systems are those that burn eastern bituminous coal, which has relatively high sulfur
content, so the vast majority of the data request plants are located in the eastern United States.
Figure 2-3 presents the geographic distribution of the data  request plants. Chapter 3 summarizes
the information collected through the data request, including the types of FGD wastewater
treatment systems  currently operating (as  of 2006) and planned at the data request plants.

       EPA distributed the data request to the nine selected power companies in May 2007 and
received data request responses in August and October 20072.  The data requests were divided
into two parts: Part A, General Power Company Information; and Part B, Power Plant Technical
Information.  EPA requested that each power company complete Part A of the data request and
complete Part B of the data request for each coal-fired power plant they operate that meets the
following criteria:  was in operation in calendar year 2006;  and operates at least one wet FGD
system and/or is currently constructing/installing (or plans to begin constructing prior to
December 31, 2010) at least one wet FGD system.
 EPA received data request responses from each of the nine data request respondents in August 2007. One of the
data request respondents provided a Part B response for one data request plant in October 2007.	
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2007/2008 Detailed Study Report
Chapter 2 - Data Collection Activities
   Table 2-4. Profile of Coal-Fired Power Plants Operated by Data Request Respondents





Company
Number
1
2
3
4
5
6
7
8
9
Total

Coal-Fired Power Plants Operated by Data
Request Respondents


Total
No. of
Plants
10
6
16
8
10
o
5
8
4
2
67
Number
Currently
Operating
Wet FGD
Systems b
3
1
2
1
1
3
1
2
2
16
Number Not Currently
Operating Wet FGD
Systems, But Planning to
Begin Constructing by
12/31/2010 b
2
1
1
3
4
0
2
0
0
13d
Plants for which Data Request
Respondents Provided Technical
Information a


Total
No. of
Plants
5
2
3
4
6
3
3
2
2
30 d
Number with
Segregated FGD
Wastewater
Treatment System
(Operating) b
0
1
0
1
1
0
1
0
0
4


Number with
Wet Fly Ash
Systems c
0
1
1
2
6
o
3
2
0
2
17
Source: [U.S. EPA, 2008a]
a - Plants within the scope of Part B of the data request.
b - Based on information provided in the data request responses, as of August 2007.
c - Prior to completing the data request, companies provided EPA with preliminary information about their coal-
fired power plants. At that time, the number of plants with wet fly ash systems totaled 20. Based on information
provided in response to the data request, the total number of plants with wet fly ash systems is actually 17.
d - EPA received data request technical information for 30 coal-fired power plants. One company responded to the
data request with plans to install wet FGD systems at one plant by December 31, 2010; however, during follow-up
communications with EPA, the  company informed EPA that they have since decided not to install FGD systems as
part of the company's long-term air pollution control strategies.

       Part A requested the following: company contact information; corporate structure
information; and profile information for the coal-fired power plants that the companies currently
operate and that were in operation during 2006. Part B contained the following seven sections:

       •       Section 1: General Plant Information;
       •       Section 2: Steam Electric Power Production;
       •       Section 3: Fuels Used;
       •       Section 4: Process Wastewater Generation  from Coal-fired Steam Electric Units;
       •       Section 5: Wastewater Discharge and Treatment Operations;
       •       Section 6: Wastewater Treatment Costs; and
       •       Section 7: Monitoring Data.

       Section 1 (General  Plant Information) requested plant address and contact information.
Sections 2 and 3  (Steam Electric Power Production; Fuels Used) requested steam electric power
production information and fuels used for each steam electric unit that the plant operated in
2006.
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2007/2008 Detailed Study Report                                  Chapter 2 - Data Collection Activities


    Legend
     O  Currently operating one or m
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2007/2008 Detailed Study Report                                  Chapter 2 - Data Collection Activities
       Section 7 (Monitoring Data) requested monitoring data for coal-fired steam electric
wastewater streams that the plant collected for any reason during 2006 that meets certain sample
location and analyte criteria.

       In developing the data request, EPA worked with industry trade associations and other
EPA program offices to develop questions that addressed the needs of the 2007/2008 detailed
study while minimizing respondent burden. After distributing the  data request to the nine data
request respondents, EPA provided assistance and clarification regarding the data request
questions directly via a help line and indirectly via UWAG.

       EPA conducted a technical review of the data request responses to ensure the quality and
consistency of the data.  Following the technical review of each data request response, EPA
communicated with the  data request respondents to resolve questions and/or discrepancies found.
Once resolved, EPA key-entered the revised data request responses into a database and
performed a quality assurance check of the key-entered data. [ERG, 2008i]

       A portion of the  information provided by data request respondents was claimed as
confidential business information (CBI).  In these cases, EPA has provided sanitized versions of
the original data request responses, documentation of follow-up communications with data
request respondents, and the database of data request information in the  docket for the 2008
Effluent Guidelines Program Plan.

2.4    Interactions with UWAG

       UWAG is an association of over 200 individual electric utilities and four national trade
associations of electric utilities: the Edison Electric Institute, the National Rural Electric
Cooperative Association, the American Public Power Association, and the Nuclear Energy
Institute.  The individual utility companies operate power plants and other facilities that generate,
transmit, and distribute electricity to residential, commercial, industrial,  and institutional
customers. The Edison  Electric Institute is the association of U.S.  shareholder-owned electric
companies, international affiliates, and industry associates.  The National Rural Electric
Cooperative Association is the association of nonprofit electric cooperatives supplying central
station service through generation, transmission, and distribution of electricity to rural areas of
the United States. The American Public Power Association is the national trade association that
represents publicly owned (municipal and state) electric utilities in 49 states.  The Nuclear
Energy Institute establishes industry policy on legislative, regulatory, operational, and technical
issues affecting the nuclear energy industry on behalf of its member companies, which include
the companies that own  and operate commercial nuclear power plants in the United States, as
well as nuclear plant designers and other organizations involved in the nuclear energy industry.
UWAG's purpose is to participate on behalf of its members in EPA's rulemakings under the
CWA.

       UWAG commented on EPA's selection of the steam electric power generation industry
for a detailed study as part of the 2006 Effluent Guidelines Program Plan and submitted
comments to EPA regarding the detailed study as part of the preliminary 2008 Effluent
Guidelines Program Plan. UWAG also provided data during a review of PCS and TRI data to
assess national discharge loadings associated with this  industry, as summarized in the Interim
Detailed Study Report for the Steam Electric Power  Generating Point Source Category

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2007/2008 Detailed Study Report                                  Chapter 2 - Data Collection Activities
(EPA/821-R-06-015, November 2006) [U.S. EPA, 2006b]. As EPA continued with the
2007/2008 detailed study and began formulating approaches to data collection, EPA held a series
of discussions with UWAG to streamline and facilitate the data collection process. Specifically,
EPA communicated with UWAG to collect information on power plant characteristics to support
site visit selection, discuss wastewater sampling approaches and recommendations, review the
data request for clarity, and coordinate data collection for existing permit data.

2.4.1   Database of Power Plant Information

       In preparing for selecting site visit candidates, EPA assembled available power plant
information from the Department of Energy (DOE) and EPA's Office of Air and Radiation.
Specifically, EPA was interested in coal-fired power plants that operate wet FGD systems and
have wet ash handling operations.  As discussed in Section 2.1, EPA provided UWAG with a list
of 96 potential candidates, on which UWAG provided information. Section 3.1 summarizes the
data provided by UWAG.

2.4.2   Wastewater Sampling

       As discussed in Section 2.2, EPA is conducting a sampling program to characterize
wastewaters generated by coal-fired power plants, and to evaluate treatment technologies and
best management practices available to reduce pollutant discharges. EPA held several meetings
with UWAG to discuss various approaches to the sampling program,  including identifying
representative sample points, providing comment on the generic sampling and analysis plan, and
providing recommendations on laboratory analyses and potential interferences (particularly with
handling influent samples with high concentrations of solids).  UWAG participated in the facility
pre-sampling site visits and provided review and comment on site-specific sampling plans.  At
the  invitation of the plants being sampled, UWAG also collected split samples during EPA's
sampling episodes. EPA held a meeting with UWAG to discuss the FGD effluent sampling
results for four of the plants that have been sampled. During this meeting, EPA and UWAG
compared analytical results and discussed the challenges associated with analyzing the FGD
wastewaters. [ERG, 2008c]

2.4.3   Data Request

       As discussed in Section 2.3, EPA developed a data request to  collect information on coal-
fired power plants.  EPA provided UWAG an opportunity to review the data request and to
recommend changes to improve the clarity of the questions involved. For example,  UWAG
provided input on the industry's definitions of scrubber terminology to ensure that the
respondents would understand the questions that EPA included in the request.  After EPA
distributed the data request to the data request respondents, UWAG requested clarification
regarding certain data request questions on behalf of its members. Copies of UWAG's
comments and questions on the data request are included in the docket [UWAG, 2007].

2.4.4   NPDESForm2C

       UWAG and EPA coordinated efforts to create a database of selected National Pollutant
Discharge Elimination System (NPDES) Form 2C data from UWAG's member companies. The
NPDES Form 2C (or an  equivalent form used by  a state permitting authority) is an application

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2007/2008 Detailed Study Report                                 Chapter 2 - Data Collection Activities
for a permit to discharge wastewater that must be completed by existing industrial facilities
(including manufacturing, commercial, mining, and silvicultural operations). This form includes
facility information, data on facility outfalls, process flow diagrams, treatment information, and
intake and effluent characteristics.

       The NPDES Form 2C database is focused on the outfalls of coal-fired power plants that
receive FGD, ash handling, or coal pile runoff waste streams.  Other outfalls - such as separate
outfalls for sanitary wastes, cooling water, landfill runoff, and other waste streams - were not
included in the database. The database does not include Form 2C information for plants that
have neither a wet FGD system nor wet fly ash handling. For example, if a plant has no wet
FGD system and it is known that the only wet ash handling at the plant is for bottom ash
sluicing, its information was not included in the database.

       UWAG originally anticipated that these data would be available in December 2007;
however, this effort was delayed and EPA received Form 2C data for 86 plants in late June 2008.
[UWAG, 2008]

2.5    Interactions with EPRI

       EPRI is a research-oriented trade association for the steam electric industry. EPRI
conducts research funded by the steam electric industry and has extensively studied wastewater
discharges from FGD systems, and provided EPA with the following reports that summarize the
data collected during several of these studies:

       •      Flue Gas Desulfurization (FGD) Wastewater Characterization: Screening Study
             [EPRI, 2006a];

       •      EPRI Technical Manual: Guidance for Assessing Wastewater Impacts of FGD
             Scrubbers [EPRI, 2006b];

       •      The Fate of Mercury Absorbed in Flue  Gas Desulfurization (FGD) Systems
             [EPRI, 2005];

       •      Update on Enhanced Mercury Capture by Wet FGD: Technical Update [EPRI,
             2007b]; and

             PISCES Water Characterization Field Study, Sites A-G [EPRI, 1997-2001].

The EPRI reports have provided EPA with background information regarding the characteristics
of FGD wastewaters and the sampling techniques used to collect the samples.

       In addition, EPRI participated in meetings with EPA and provided comments on EPA's
planned data collection activities, including the data request and the sampling program.  EPRI
specifically commented on the sample collection techniques and considerations for laboratory
analysis of FGD and ash handling wastewaters. EPRI also provided comments on EPA's
Generic Sampling and Analysis Plan for Coal-fired Steam Electric Power Plants. A copy of
EPRI's comments on the sampling plan is included in  the docket [EPRI, 2007c].

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2007/2008 Detailed Study Report                                   Chapter 2 - Data Collection Activities
2.6    Department of Energy (DOE)

       DOE promotes scientific and technological innovation in support of its mission to
advance the national, economic, and energy security of the United States.  DOE's goals toward
achieving this mission include applying advanced science and nuclear technology to the U.S.'s
defense, promoting a diverse supply and delivery of reliable, affordable, and environmentally
sound energy, advancing scientific knowledge, and providing for the permanent disposal of the
U.S.'s high-level radioactive waste.  In the 2007/2008 detailed study, EPA used information on
electric generating facilities from DOE's Energy Information Administration (EIA) data
collection forms.

       EIA is a statistical agency of the DOE that collects information on existing U.S. electric
generating facilities and associated equipment to evaluate the current status and potential trends
in the industry.  EPA used information from two of EIA's data collection forms: Form EIA-860,
Annual Electric Generator Report, and Form EIA-767, Steam Electric Plant Operation and
Design Report.  These forms are discussed below.

2.6.1   Form EIA-860

       Form EIA-860 collects information annually for all electric generating  facilities that have
or will have a  nameplate rating3 of one megawatt (MW) or more, and are operating or plan to be
operating within five years of the filing of the Annual Electric Generator Report.  The data
collected in Form EIA-860 are associated only with the design and operation of the generators at
facilities [U.S. DOE, 2005a].

2.6.2   Form EIA-767

       Form EIA-767 collects information annually from all electric generating facilities with a
total existing or planned, organic-fueled or renewable steam electric generating unit that has a
nameplate rating of 10 MW or larger. The data collected in Form EIA-767 is associated with the
operation and  design of the entire facility.  EPA used Form EIA-767 primarily for information on
the facilities operating (or planning to operate) FGD systems [U.S. DOE, 2005b].
3 DOE defines the generator nameplate capacity as the maximum rated output of a generator under specific
conditions designated by the manufacturer. Generator nameplate capacity is usually indicated in units of kilovolt-
amperes (kVA) and in kilowatts (kW) on a nameplate physically attached to the generator. More generally,
generator capacity is the maximum output, commonly expressed in megawatts (MW), that generating equipment can
supply to system load, adjusted for ambient conditions.	
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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
3.     OVERVIEW OF THE COAL-FIRED STEAM ELECTRIC INDUSTRY

       As discussed in Chapter 2, EPA's 2007/2008 detailed study of the steam electric power
generating industry focused on wastewater discharges from coal-fired power plants. Specifically
of interest are wet FGD and ash handling wastes. As such, this chapter presents an overview of
coal-fired power plants within the steam electric industry, with particular emphasis on those
operating (or planning to operate) wet FGD systems. For a detailed profile of the steam electric
industry in relation to the electric generating industry as a whole, see Chapter 3.0 of the Interim
Detailed Study Report for the Steam Electric Power Generating Point Source Category (EPA-
821-R-06-015; November 2006) [U.S. EPA, 2006b]4.

       The wastewater information presented in this chapter is focused on FGD and ash sluice
wastewater, which EPA believes to be two of the primary sources of metals discharged from
coal-fired power plants. This chapter also presents available information about coal pile runoff,
which can contribute a significant amount of metals to plant discharges.

       As part of the collection activities for the data request, EPA collected information
regarding wastewater generation flow rates for cooling water (once-through and cooling tower
blowdown), pyritic mill reject sluice, air preheater washwater, and other miscellaneous low-
volume wastewaters [U.S. EPA, 2008a]. The data for these waste streams are not presented in
this report.  For a description of other steam electric unit operations  and sources of wastewater
generation, see Section 3.2 of the Interim Detailed Study Report for the Steam Electric Power
Generating Point Source Category (EPA-821-R-06-015; November 2006) [U.S. EPA, 2006b].

3.1     Flue Gas  Desulfurization Systems

       Power plants use FGD systems to control sulfur dioxide (862) emissions from the flue
gas generated in the plants' boiler.  Wet FGD scrubbers are the most common type of FGD
system; however, dry FGD systems also exist [U.S. EPA, 2003]. The 2007/2008 detailed study
is focused on wastewaters from wet FGD systems only. There are several variations of wet FGD
systems,  but this section focuses on the limestone forced oxidation system and the lime or
limestone non-forced  oxidation system, as EPA believes these are the most common systems in
the industry.

       EPA has compiled information on the current or planned use of wet FGD systems at 91
plants (198 generating units), using information collected from the site visit and sampling
program, the  data request, and the UWAG-provided information.  The wet FGD systems at 95 of
the  198 generating units (48 percent) are currently or will be forced  oxidation systems, and the
wet scrubbers at 67 of the generating units  (34 percent) are natural or inhibited oxidation
systems.  The remaining 36 generating units (18 percent) are currently or will be scrubbed by
wet FGD systems installed after 2006.  Although EPA did not collect information on the
4 The detailed profile of the steam electric industry presented in Section 3.0 of the Interim Detailed Study Report for
the Steam Electric Power Generating Point Source Category [U.S.EPA, 2006a] is based on 2002 data. Although it
is not as current as the data provided in this section, it does provide a picture of the coal-fired steam electric industry
in relation to the entire steam electric industry, as well as a picture of the steam electric industry in relation to the
entire electric generating industry. EPA has not updated the data for the entire steam electric industry or electric
generating industry as the focus of the 2007/2008 Steam Electric Detailed Study is on coal-fired power plants.	
                                           3-1

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
oxidation process for scrubbers planned for these generating units, based on industry trends EPA
expects they will be forced oxidation systems.

       Limestone is by far the predominant sorbent used in wet FGD systems (74 percent of
generating units), followed by lime (14 percent of generating units) and magnesium-enhanced
lime (7 percent of generating units). Magnesium oxide, fly ash, and soda ash sorbents
collectively are used in wet scrubbers at 5 percent of generating units.

3.1.1   Process Description  and Wastewater Generation

       This section describes the steam electric generating processes for wet limestone forced
oxidation FGD systems and  wet lime or limestone non-forced oxidation FGD systems based on
data collected by EPA throughout the 2007/2008 detailed study.

       3.1.1.1   Limestone Forced Oxidation FGD Scrubbers

       To date, the EPA site visit and sampling program primarily focused on limestone forced
oxidation systems because these types of FGD systems are the most predominant systems
operating segregated wastewater treatment systems prior to discharging FGD wastewater. In
addition, based on discussions with industry representatives, EPA expects that the majority of
future wet FGD systems will be limestone forced oxidation. Of the  14 power plants that EPA
visited between December 2006 and May 2008 that were operating an FGD system at the time of
the visit, 13 were operating limestone forced oxidation FGD systems. The two plants that EPA
visited that were not operating FGD systems are both in the process  of installing limestone
forced oxidation FGD  systems.

       The limestone forced oxidation FGD system works by contacting the flue gas stream with
a liquid slurry stream containing a limestone (CaCO3) sorbent, which effects mass transfer.
Equation 3-1 shows the reaction that occurs between limestone and sulfur dioxide,  producing
hydrated calcium sulfite (CaSO3) [EPRI, 2006a].

               CaCO3 (s) + SO2 (g) + 1/2 H2O -> CaSO3 x 1/2 H2O (s) + CO2 (g)           (3-1)
       The calcium sulfite is then oxidized to calcium sulfate (gypsum) by injecting air into the
calcium sulfite slurry. Equation 3-2 shows the reaction producing gypsum (CaSO4* 2H2O) from
calcium sulfite [EPRI, 2006a].

              CaSO3 x 1/2 H2O (s) + '/2 O2 (g) + 3/2 H2O 0)  ->  CaSO4 x 2H2O (s)          (3-2)
       During the site visits to power plants operating limestone forced oxidation FGD systems,
EPA determined that the operation of these FGD systems varies somewhat by plant; however,
most of the systems follow the same general operating procedure. Figure 3-1 presents a typical
process flow diagram for a limestone forced oxidation FGD system, based on EPA's
observations during the site visit and sampling program.

       Most of the plants EPA visited operate a spray or tray tower FGD scrubber, in which the
flue gas and the limestone slurry are configured with countercurrent flow.  The flue gas enters
near the bottom of the FGD scrubber and the limestone slurry and scrubber slurry recycle are

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
pressurized and sprayed downward from several different spray levels near the top of the FGD
scrubber.  The spray droplets of the limestone slurry contact the flue gas and absorb the sulfur
dioxide, which reacts with the limestone (see Equation 3-1). To increase the sulfur dioxide
removal efficiency, some plants use additives (e.g., dibasic acid (DBA) or formic acid) in the
FGD system. These additives buffer the scrubber slurry, which controls the sulfur dioxide vapor
pressure in the scrubbers, thereby maximizing the sulfur dioxide absorption rate [Babcock &
Wilcox, 2005]. See Section 3.1.2.1 for more information on the types of additives used by coal-
fired power plants. The scrubbed flue gas then exits out the top of the FGD scrubber through a
mist eliminator and then to the stack.

       The spray droplets, some containing the calcium sulfite product and others with
unreacted limestone, fall to the bottom of the FGD scrubber into a reaction tank.  The plant
injects air into the reaction tank and vigorously mixes the slurry to oxidize the calcium sulfite to
gypsum (see Equation 3-2).  The plant uses the scrubber recycle pumps to pressurize and pump
the slurry from the reaction tank to the various spray levels within the FGD scrubber.  The plant
continuously recirculates the slurry in the FGD scrubber. When the percent solids or the
chlorides concentration in the slurry reach a certain high set point, the plant uses the scrubber
blowdown pumps to remove some of the slurry from the FGD scrubber. The plant uses this
blowdown stream to reduce the levels of solids and chlorides in the scrubber slurry until a low
set point is reached within the FGD scrubber. The plant then shuts off the blowdown pumps
until the solids and chlorides build up again to the point of triggering a blowdown. Therefore,
the scrubber blowdown is typically an intermittent transfer from the scrubber.  Some plants,
however, operate an FGD scrubber with a continuous blowdown,  which can either be a once-
through FGD system with no recycle, or an FGD system that recycles some of the slurry but is
constantly blowing down slurry to keep  the solids and chlorides level at a constant set point.

       The parameter used to control the FGD system (i.e., percent solids or chlorides
concentration) and the level at which it is controlled varies by plant. Plants control the chlorides
level in the FGD system based on the metallurgy of the  FGD scrubber materials of construction.
Plants maintain a chlorides concentration well below that which the FGD scrubber materials of
construction can withstand, normally around 12,000 - 20,000 ppm; however, some systems
operate with chloride concentrations as low as 4,000 to 6,000 ppm and other plants may operate
near 30,000 ppm. Plants that produce gypsum for beneficial reuse must also monitor/control the
FGD system based on the percent solids because the plant must limit the amount of fines (small
inert particles) in the gypsum by-product [EPRI, 2006a].

       The scrubber blowdown, which is a gypsum slurry, is transferred to a dewatering process.
Often, this process uses one or two sets of hydrocyclones, referred to in the industry as
hydroclones.5  The hydroclones separate the gypsum solids from the water using centrifugal
force. The gypsum solids are forced outward to the walls of the hydroclones and fall downward,
while the water exits the top of the hydroclones. The underflow from the first set of
hydroclones, referred to as the primary hydroclones, contains the gypsum solids and is
transferred to vacuum filter belts.  The primary hydroclone overflow, which is mostly water and
fines, is transferred to the primary  hydroclone overflow head tank.
5 Another approach for solids removal practiced by some plants entails the use of settling ponds instead of
hydroclones or other mechanical devices.	
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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry


       The primary hydroclone underflow sent to the vacuum filter belts is rinsed with service
water to reduce the chlorides concentration if the plant intends to market the gypsum for
beneficial reuse, such as for wallboard production. The vacuum filter belts then remove the
water from the gypsum, drying the gypsum to its desired moisture content. At the end of the
vacuum filter belts, the gypsum falls off the belts and is conveyed to a storage area until it is
transported off site. Plants that do not sell the gypsum may dispose of it in an on-site landfill.
Filtrate from the vacuum filter belt is recovered in a reclaim tank and either returned to the FGD
scrubber or used in the limestone slurry preparation process.

       The primary hydroclone overflow is often transferred from the primary hydroclone head
tank to a second set of hydroclones, as shown in Figure 3-1. The second set of hydroclones is
typically operated at plants treating the scrubber purge in an FGD wastewater treatment system
other than a settling pond.  These secondary hydroclones remove most of the remaining fines
from the wastewater, which reduces the overall solids load to the FGD wastewater treatment
system. The secondary hydroclones operate the same as the primary hydroclones, except that
they remove far fewer solids than the primary hydroclones and the solids removed are fines;
therefore, the secondary hydroclone underflow is sent to the reclaim tank and returned to the
scrubber.  The secondary hydroclone overflow is sent to the purge tank.

       From the purge tank, the  scrubber purge6 is typically transferred to some type of FGD
wastewater treatment system, which could be a settling pond or a more advanced system (see
Section 3.1.4).  It may also be commingled with other wastewater streams  (e.g., once-through
cooling water) and discharged. Because most treatment systems in use do  not significantly
change the chlorides concentration, the stream is not recycled back to the FGD scrubber unless
the plant operates the solids removal process in a manner that purges the excess chlorides along
with the solids. If the plant does not have specifications for the chlorides or fines content in the
gypsum by-product, then it is possible for the plant to recycle the secondary hydroclone overflow
without a purge stream because the chlorides can be removed from the FGD system by retaining
the chlorides with the solids that are  sent to a landfill. Most of the plants that sell the gypsum for
beneficial reuse do have chloride and fines specifications, but plants that dispose of the gypsum
in a landfill may not need a scrubber purge stream [Sargent & Lundy, 2007].
6 For the purpose of this document, the scrubber blowdown refers to the slurry stream exiting the FGD scrubber
which is not immediately recycled (typically transferred to a solids separation process).  The scrubber purge refers to
the waste stream from the FGD scrubber system (typically from a solids separation process) that is transferred to a
wastewater treatment system or discharged. Both the scrubber blowdown and scrubber purge waste streams are
depicted in Figure 3-1.  In some instances, the scrubber blowdown and scrubber purge may be the same waste
stream if the plant does not operate a solids separation process prior to wastewater treatment or discharge.	
                                            3-4

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2007/2008 Detailed Study Report
                                                     Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
   Limestone
  Slurry Feed
                                 Flue Gas From
                                 FGD Scrubber
            Scrubber
          Slurry Recyle
            Scrubber
          Recycle Pumps
                             Reaction Tank
                    Air Injection
 Flue Gas To
FGD Scrubber
        Scrubber
     Slowdown Pumps
                                      Reclaim To FGD
                                         Scrubber
                     Primary Hydroclone
                         Overflow
                                                      Reclaim Pump
                                                                     Primary
                                                                   ' Hydroclone
                             Secondary
                         Hvdroclone Overflow
                                                                       Primary Hydroclone   Secondary Hydroclone
                                                                       Overflow Head Tank       Feed PumP

                                                                          Secondary Hydroclone Underflow
                                           Vacuum Belt Filter
                                         -H_ฃ
Vacuum Belt Filter
     Filtrate
                                                                 Secondary
                                                                 Hydroclone
                                                                      Purge Tank
                                                                                                          Gypsum Cake
                                                                                                            To Storage
                                                                                                                                Scrubber Purge to
                                                                                                                                FGD Wastewater
                                                                                                                                   Treatment
                                                                     Reclaim Tank
                    Figure 3-1. Process Flow Diagram for a Limestone Forced Oxidation FGD Scrubber System

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       3.1.1.2    Lime or Limestone Non-Forced Oxidation FGD Scrubbers

       As described in Section 3.1.1.1, the EPA site visit and sampling program primarily
focused on limestone forced oxidation FGD systems; however, lime or limestone non-forced
oxidation FGD systems are also prevalent in the steam electric industry. Many of these plants do
not operate wastewater treatment systems, other than settling ponds, to treat the scrubber purge.
In addition, some plants are able to recycle their FGD wastewater back to the FGD system and,
therefore, do not produce a scrubber purge waste stream.

       The lime or limestone non-forced oxidation FGD systems work by contacting the flue gas
stream with a liquid slurry stream containing a lime (Ca(OH)2) or limestone (CaCOs) sorbent,
which effects mass transfer. Equation 3-1 shows the reaction between limestone and sulfur
dioxide and Equation 3-3 shows the reaction that occurs between lime and sulfur dioxide,
producing hydrated calcium sulfite (CaSOs).

                   Ca(OH)2 (s) + SO2 (g) -> CaSO3 x y2 H2O (s) + V2 H2O 0)               (3-3)

       Figure 3-2 presents a typical process flow diagram for a lime or limestone non-forced
oxidation FGD system. Most of these FGD systems are spray or tray tower FGD scrubbers, in
which the flue gas and the lime or limestone slurry are configured with countercurrent flow. The
flue gas enters near the bottom of the FGD scrubber, and the slurry and scrubber slurry recycle
are pressurized and sprayed downward from several different spray levels near the top of the
FGD scrubber.  The spray droplets of the slurry contact the flue gas and absorb the sulfur
dioxide, which reacts with the lime or limestone (see Equations 3-3 or 3-1,  respectively).  To
increase the sulfur dioxide removal efficiency, some plants use additives (e.g., dibasic acid
(DBA) or formic acid) in the FGD system. These additives buffer the scrubber slurry, which
controls the sulfur dioxide vapor pressure in the scrubbers, thereby maximizing the sulfur
dioxide absorption rate [Babcock & Wilcox, 2005]. See Section 3.1.2.1 for more information on
the types of additives used by coal-fired  power plants. The scrubbed flue gas then exits the top
of the FGD scrubber, through a mist eliminator,  and then to the stack.

       The spray droplets,  some containing the calcium sulfite product and others with
unreacted lime or limestone, fall to the bottom of the FGD scrubber. This scrubber slurry is
collected at the bottom of the FGD scrubber and the plant uses the scrubber recycle pumps to
pressurize and pump the slurry from the  bottom of the scrubber to the various spray levels within
the FGD scrubber.  The plant continuously recirculates the slurry in the FGD scrubber. When
the percent solids or the chlorides concentration in the slurry reach a certain high set point, the
plant uses the scrubber blowdown pumps to remove some of the slurry from the FGD scrubber
system. The plant uses this blowdown stream to reduce the levels of solids and chlorides  in the
scrubber slurry until a low set point is reached within the FGD scrubber.  The plant then shuts off
the blowdown pumps until the solids  and chlorides build up again to the point of triggering a
blowdown. Therefore, the scrubber blowdown is typically an intermittent transfer from the
scrubber.  Some plants, however, operate an FGD scrubber with a continuous blowdown,  which
can either be a once-through FGD system with no recycle, or an FGD system that recycles some
of the slurry, but is constantly blowing down slurry to keep the solids and chlorides level at a
constant set-point.  The parameter used to control the FGD system (i.e., percent solids or
chlorides concentration) and the level at  which it is controlled varies by plant.

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       The scrubber blowdown, which is a calcium sulfite slurry, is transferred to a dewatering
process (e.g., thickener, centrifuge, settling pond, vacuum drum or belt filter).  The solids from
this initial dewatering step are intermittently pumped to a final dewatering process consisting of
either a vacuum filter or centrifuges, although plants operating a vacuum drum filter as the first
dewatering step are not likely to operate an additional vacuum filter for final dewatering.
Likewise, settling pond systems typically will not operate a final mechanical dewatering process.
The solid cake from the final dewatering process is sent to a landfill, either on or off site. The
overflow from the thickener or vacuum drum filter is sent to a reclaim tank, from which some
wastewater may be recycled back to the FGD scrubber and some may be discharged or
transferred to additional treatment. The filtrate from the dewatering process is also collected in a
reclaim tank and discharged or recycled back to the FGD scrubber.  For a plant operating a
settling pond to dewater the scrubber blowdown, the solids from the settling pond are either
retained in the pond or dredged and landfilled. The overflow from the settling pond is either
discharged from the plant, or recycled to the scrubber if chlorides have been sufficiently
removed from the waste stream.

       Plants operating non-forced oxidation FGD systems typically operate settling ponds for
the treatment of the scrubber purge waste stream. Because the non-forced oxidation systems
typically do not generate a sellable solid product, the  solids are typically disposed of in a landfill.
Like the limestone forced oxidation systems not beneficially reusing the gypsum, it may be
possible for the plant to recycle the FGD wastewater without a purge stream because the
chlorides can be removed from the FGD system by retaining the chlorides with the solids that are
sent to the landfill [Sargent & Lundy, 2007]. Therefore, the plants operating non-forced
oxidation FGD systems may not need a scrubber purge stream.

3.1.2  Coal-Fired FGD System Statistics

       This section presents statistics on the number  and characteristics of coal-fired power
plants that have FGD systems or are planning to install them. Also included in this section are
estimates of the coal-fired steam electric industry's historic, current, and projected total
generating capacity and scrubbed capacity.

       3.1.2.1    Current Coal-Fired FGD System Profile

       This section presents a picture of the current coal-fired steam electric industry regarding
number of coal-fired power plants with FGD systems, the associated scrubbed capacity, and
plant characteristics.  The data  sources used for this profile include UWAG-provided data [ERG,
2008f], EPA's site visit and sampling data, EPA's data request information [U.S. EPA, 2008a],
and the 2005 Form EIA-767  [U.S. DOE, 2005b]. See Chapter 2 for background regarding
EPA's data collection activities.

       Table 3-1 presents statistics on the current (as of June 2008) coal-fired steam electric
power generation associated with FGD systems as compared to the broader coal-fired and fossil-
fueled steam electric power generation.  As shown in Table 3-1, approximately 32 percent of the
coal-fired steam electric power generating capacity is currently associated with wet FGD
systems.  EPA expects that percentage to increase significantly in the future, as discussed in
Section 3.1.2.2.
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                                        Flue Gas From
                                           Scrubber
           Lime/
         Limestone
        Slurry Feed
oo
                   Scrubber
                 Slurry Recyle
                  Scrubber
                Recycle Pumps
                                                         Stack
FGD Scrubber
               Flue Gas To
              FGD Scrubber
                                  I
                                 T3
                                 _g
                                 CO
                                  &
                                 _Q
                                  O
                                 C/3
    4-

 Thickener
CD
O
                      Scrubber
                   Slowdown Pumps
                                                                                                                  Dewatering:
                                                                                                                 Vacuum Filter or
                                                                                                                  Centrifuges
                                                                                     Thickener
                                                                                     Underflow
                                                                                                    Thickener
                                                                                                   Sludge Pump
                                                                                                                                    Solid Cake To
                                                                                                                                      Disposal
                                                                                            Dewatering Filtrate
                                        Reclaim To Scrubber
                                                             Reclaim Pump
                                                                            Reclaim Tank
                      Figure 3-2. Process Flow Diagram for a Lime or Limestone Non-Forced Oxidation FGD Scrubber

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
     Table 3-1. Scrubbed Coal-Fired Steam Electric Power Generation as of June 2008






Number of Plants6
Number of
Generating Units e> f
Capacity (MW)e'g


Fossil-Fueled
Steam Electric
Power
Generation a' b
957
2,430

488,000

Coal-Fired
Steam
Electric
Power
Generation a
497
1,280

329,000

Coal-Fired Steam
Electric Power
Generation with
Any FGD System
(Wet or Dry) c
146
290

120,000 h
Coal-Fired
Steam Electric
Power
Generation with
a Wet FGD
System c'd
107
222

104,000 h
Coal-Fired
Steam Electric
Power
Generation with
a Dry FGD
System c'd
43
68

16,200 h
a - Source: 2005 EIA-767 [U.S. DOE, 2005b]. Includes units identified in the EIA as planned or under construction
that were expected to be operating by the end of 2007.
b - Fossil-fueled generation includes coal, oil, and natural gas. It does not include nuclear generation.
c - Source: 2005 EIA-767 [U.S. DOE, 2005b] (including units associated with FGD scrubbers that were planned or
under construction for 2007), UWAG-provided data [ERG, 2008f], data request information [U.S. EPA, 2008a], and
site visit and sampling information.
d - The wet and dry scrubbed information is a subset of the information for "Any FGD System." Note that several
plants operate both wet  and dry FGD systems. Thus, there is overlap between the number of plants with wet FGD
systems and the number of plants with dry FGD systems.
e - The numbers presented have been rounded to three significant figures.
f - The number of units represents the number of generating units scrubbed and does not represent the number of
FGD systems; however, the two numbers are similar, but several plants use a single FGD scrubber for more than one
generating unit.
g - The capacities for the EIA-767 data represent the reported nameplate capacity. The capacities for the UWAG-
provided data, data request information, and site visit and sampling information are based on information provided
to EPA and may represent various capacities (e.g., nameplate capacity, net summer capacity, gross winter capacity).
h - Includes only the capacity for the scrubbed units.

       EPA used the following three data sources to compile plant characteristic information for
a subset  of all coal-fired power plants that operate FGD  systems: UWAG-provided data, EPA's
site visit and sampling data, and EPA's data request information.  The collective data from these
three data sources is referred to hereinafter as the "combined data set."  The vast majority of the
steam electric capacity included in these data sources is wet scrubbed, as that was the focus of
EPA's data collection effort.

       Table 3-2 presents the percentage  of scrubbed capacity that the combined data set
represents relative to EPA's estimate of the current and planned total scrubbed capacity.  The
planned units included in Table 3-2 are only for plants for which EPA collected information
from the UWAG-provided data, data request, or the site visit and sampling program, and does
not include many other plants and generating units that will install new FGD scrubbers over the
next 10 to 15 years.

       Table 3-3 summarizes plant characteristics for the wet scrubbed units included in the
combined data set.  EPA presents these data as a general picture of the current wet scrubbed,
coal-fired steam electric industry; however, it should be noted that the combined data set also
includes a relatively small number of FGD systems that are planned to begin operation over the
next several years.  As is the case for Table 3-2, the planned units included in Table 3-3 are only
for  plants for which EPA collected information  during the study.  Table 3-3 substantially under-
                                              3-9

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry


represents the population of new FGD scrubbers that will be installed over the next 10 to 15
years.  The UWAG-provided data mainly include information through the year 2006, with a few
FGD systems coming on line through 2008. The majority of the site visit and sampling
information represents conditions in place as of the date of this report, albeit with the inclusion
of a few additional generating units for which the plants are planning to install wet FGD
scrubbers.  Most of the data request information was reported for the year 2006, but the data
request also obtained information on FGD systems that were scheduled to startup or begin
construction by the end of December 2010.7

       The majority of the plants in the combined data set with FGD systems (63 percent) use
eastern bituminous coal  as the primary fuel source, which is to be expected considering eastern
bituminous coal typically contains a higher sulfur content than other coal types.  Other coals
reported include subbituminous (19 percent of plants), lignite (10 percent of plants), and other
bituminous coals (9 percent of plants).

       Over 70 percent  of the plants in the combined data set report using (or are planning to
use) limestone as the FGD sorbent.  Just under half of the plants use forced oxidation systems to
produce gypsum, while the  other half produces a calcium sulfite byproduct.  Nearly half of the
plants report using additives in their FGD systems. Of the additives used, DBA is the most
common (18  percent of total plants), followed by emulsified sulfur (10 percent of total plants).
Less commonly used additives are formic acid, adipic acid, magnesium hydroxide, and sodium
formate.

       More than half of the wet scrubbed units in the combined data set operate either an SCR
or SNCR system for NOx control (42 percent SCR; 9 percent SNCR). Twenty-nine percent of
the scrubbed  units  operate another form of NOx  control, such as low NOx burners and over-fired
air systems. Less than 15 percent of the units operate no NOx controls of any form. For details
regarding the operation of NOx control systems at power plants, see Section 3.2  of the Interim
Detailed Study Report for the Steam Electric Power Generating Point Source Category (EPA-
821-R-06-015; November 2006) [U.S. EPA, 2006b].

       No plants in the combined  data set were identified as currently operating mercury air
controls.  Several plants from the data request population reported plans to install mercury air
controls,  such as activated carbon injection systems, between 2008 and 2010.
7 The data request specified that information should be provided for FGD systems planned out through December
31, 2010; however, some plants provided information associated with FGD systems planned through 2014.	
                                          3-10

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2007/2008 Detailed Study Report
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                                   Table 3-2.  Scrubbed Capacity of EPA's Data Collection Sources

Data from All Sources
(Including EIA) a
Combined Data Set b
Number or Capacity (MW)
Percent of Data from All
Sources
Wet FGD Systems
Number of Plants with Wet FGD Systems
Number of Generating Units Wet Scrubbed
Wet Scrubbed Capacity (MW) c
116
254
123,000
91
198
103,000
78%
78%
84%
Dry FGD Systems
Number of Plants with Dry FGD Systems
Number of Generating Units Dry Scrubbed
Dry Scrubbed Capacity (MW) c
44
69
17,000
4
6
3,180
9%
9%
19%
All FGD Systems (Wet and/or Dry)
Number of Plants with a Wet and/or Dry FGD System
Number of Generating Units Scrubbed
Scrubbed Capacity (MW) c
155
324
140,000
92
204
106,000
59%
63%
75%
Note: The units associated with planned scrubbers that are included in the table are only for plants for which EPA has received additional information as part of
the study; they do not represent an industry-wide compilation for all projected new FGD scrubbers.
a - Source: 2005 EIA-767 (including units associated with FGD scrubbers planned or under construction for 2007) [U.S. DOE, 2005b], UWAG-provided data
(including units associated with planned FGD scrubbers) [ERG, 2008f], data request information (including units associated with planned FGD scrubbers) [U.S.
EPA, 2008a], and site visit and sampling information (including units associated with planned FGD scrubbers for plants that were operating FGD systems at the
time of the visit).
b - Source: UWAG-provided data (including units associated with planned FGD scrubbers) [ERG, 2008f], data request information (including units associated
with planned FGD scrubbers) [U.S. EPA, 2008a], and site visit and sampling information (including units associated with planned FGD scrubbers for plants that
were operating FGD systems at the time of the visit).
c - The capacities presented have been rounded to three significant figures.  Due to rounding, the total capacity may not equal the sum of the individual
capacities.  The capacities for the EIA-767 data represent the reported nameplate capacity. The capacities for the UWAG-provided data, data request
information, and site visit and sampling information are based on information provided to EPA and may represent various capacities (e.g., nameplate capacity,
net summer capacity, gross winter capacity).

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2007/2008 Detailed Study Report
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        Table 3-3.  Characteristics of Coal-Fired Power Plants with Wet Scrubbers

Total
Combined Data Set a
Number of Plants with
Wet FGD Scrubbers
91
Number of Wet Scrubbed
Generating Units
198
Wet Scrubbed Capacity1"
(MW)
103,000
Primary Coal Type c
Bituminous
Eastern Bituminous
Western Bituminous
Other Bituminous (Unknown)
Subbituminous
Powder River Basin
Other Subbituminous (unknown)
Lignite
65
57
5
3
17
8
9
9
151
129
15
7
34
13
21
13
76,600
63,300
8,130
5,120
18,000
8,080
9,930
8,170
Forced Oxidation
Yes
No
No Information (Planned Units)
44
38
13
95
67
36
50,400
32,400
19,900
Sorbent
Limestone
Lime
Magnesium Lime
Magnesium Oxide
Fly Ash
Soda Ash
66
13
8
2
3
1
147
27
14
3
5
2
78,000
11,000
9,680
803
2,720
530
Additives
Adipic Acid
DBA
Formic Acid
Emulsified Sulfur
Sodium Formate
Magnesium Hydroxide
No Additives
No Information (Planned Units)
1
16
3
9
2
2
50
13
2
34
4
20
3
3
95
36
930
18,800
1,530
10,400
2,430
2,600
46,100
19,900
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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
         Table 3-3. Characteristics of Coal-Fired Power Plants with Wet Scrubbers

Combined Data Set a
Number of Plants with
Wet FGD Scrubbers
Number of Wet Scrubbed
Generating Units
Wet Scrubbed Capacity1"
(MW)
NOx Controls
SCRd
SNCR
None/Other (no SCR/SNCR)
42
9
51
84
18
96
51,300
7,100
44,400
Note: The table includes data for some plants/units that plan to install wet FGD systems in the future. The units associated with
the planned wet FGD scrubbers were identified in each of the individual data sources and do not represent an industry-wide
compilation of all projected new wet FGD scrubbers.
a -Source: UWAG-provided data (including units associated with planned wet FGD scrubbers) [ERG, 2008f], data request
information (including units associated with planned wet FGD scrubbers) [U.S. EPA, 2008a], and site visit and sampling
information (including units associated with planned wet FGD scrubbers for plants that were operating FGD systems at the time
of the visit).
b - The capacities presented have been rounded to three significant figures. Due to rounding, the total capacity may not equal the
sum of the individual capacities. The capacities for the EIA-767 data represent the reported nameplate capacity. The capacities
for the UWAG-provided data, data request information, and site visit and sampling information are based on information
provided to EPA and may represent various capacities (e.g., nameplate capacity, net summer capacity, gross winter capacity).
c - Some plants/units use a blend of more than one coal in the generating units.  This table presents information for only the
primary type of coal burned in the generating unit.
d - Some of the SCRs included in the table are planned/under construction.

       3.1.2.2    Projected Use of FGD Systems at Coal-Fired Plants

       EPA evaluated the historical increase in use of FGDs since effluent guidelines were last
promulgated in 1982 and the expected trend  in the amount of coal-fired capacity that would be
scrubbed into the future.  For this evaluation, EPA used information from the Northeastern States
for Coordinated Air Use Management (NESCAUM) [NESCAUM, 2000], EIA Electric Power
Annual 2001 [U.S. DOE, 2003] EIA Electric Power Annual 2006 [U.S. DOE, 2007], EPA's
National Electric Energy Data System (NEEDS) 2006 database [U.S.  EPA, 2006c], and the
Integrated Planning Model (IPM) [U.S. EPA, 2006a] developed by EPA's Office of Air and
Radiation.

       Figure 3-3 shows how the wet scrubbed  generating capacity has increased over the nearly
three decades since the effluent guidelines were last promulgated, and also how the scrubbed
capacity is projected to increase between now and 2025. Figure 3-4 also presents information on
historical and projected scrubber use, showing the wet scrubbed capacity as a percentage  of the
total coal-fired generating capacity for the period 1977 to 2025. The historical capacities
presented in Figures 3-3 and 3-4 are from Environmental Regulation and Technology
Innovation: Controlling Mercury Emissions from Coal-Fired Boilers  [NESCAUM, 2000],
Electric Power Annual 2001  [U.S. DOE, 2003], and Electric Power Annual 2006 [U.S. DOE,
2007].  The capacities used in NESCAUM, 2000 were taken from EIA-Form 767 and could
represent nameplate, summer, or winter capacities. The coal-fired generating capacities reported
in the Electric Power Annual reports represent the net summer capacity; however, the U.S. DOE,
2003 and U.S. DOE, 2007 capacities for the  FGD system represent the nameplate capacity.  The
projected capacities presented are from estimates based on the IPM model [U.S. EPA, 2006a].
The IPM model uses a variety of capacities in its estimates, but preferentially uses  summer and
winter capacity before nameplate capacity.
                                             3-13

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       As shown in Figure 3-3, the wet scrubbed generating capacity has increased significantly
since the 1982 promulgation of the current ELGs and is expected to continue to do so into the
future.8 EPA estimates that in 1977 approximately five percent of coal-fired power plant
capacity was scrubbed using wet FGD systems, and by June 2008 that percentage had increased
to approximately 32 percent (see Table 3-1).  EPA models have predicted that by 2010, more
than half of the total coal-fired power plant capacity will be wet scrubbed.  The modeling also
projected that over 60 percent of coal-fired capacity will be wet scrubbed by 2020, and nearly 70
percent by 2025. The upward trend in wet-scrubbed capacity is expected to continue beyond
2025.  EPA predicts that the industry's dry scrubbed capacity will increase only slightly into the
future.  Table 3-4 provides additional detail on estimates of future use of FGD systems, both wet
and dry, as projected by the NEEDS  database and IPM information [ERG, 2008d].

       Based on communications with industry, EPA expects that the majority of newly
installed wet FGD systems will be limestone  forced oxidation systems that produce a
commercial-grade gypsum by-product.  All planned wet FGD systems reported in responses to
the data request will use limestone as the sorbent.  Additionally, EPA expects that the majority of
wet scrubbed steam electric units will also include SCR systems.
300 n
250
200
150
100
50
0
19
Generating Capacity (Gigawatts (GW))
Wet FGD '
*
t
t
f
^^/
/^
75 1985 1995 2005 2015 2025
Year
100n
90
80
70-
60
50-
40-
30
20
10-
0_
Percent of Total Coal-Fired Capacity (%)


^
+
/
*
*
+
t
/
^^J
r~~S
s

^ i i i i
1975 1985 1995 2005 2015 2025
Year
    Figure 3-3. Wet Scrubbed Generating
             Capacity, 1977-2025

Source: [ERG, 2008e]
       Figure 3-4.  Wet Scrubbed Capacity as a
          Percentage of the Total Coal-Fired
            Generating Capacity, 1977-2025
8 EPA projected future generating capacity with FGD systems using IPM Base Case 2006 (v.3.0), which reflects the
Clean Air Mercury Rule (CAMR) mercury reduction requirements and the Clean Air Interstate Rule (CAIR) NOx
and SO2 emission reduction requirements for power plants. On February 8, 2008, the D.C. Circuit Court of Appeals
vacated CAMR. (State of New Jersey v. EPA. 517 F.3d 574 (D.C. Cir. 2008)). The mandate effectuating the vacate
was issued on March 14, 2008.  On May 21, 2008, the D.C. Circuit denied EPA's request that the full court
reconsider the vacate. The parties have until September 17, 2008, to request that the  Supreme Court review the
D.C. Circuit's decision. In a separate action, on July 11, 2008, the D.C. Circuit issued a decision vacating CAIR.
(North Carolina v. EPA. 531 F.3d 896 (D.C. Cir. 2008)) The court's mandate in that case has not yet issued. Parties
may ask the D.C. Circuit to reconsider its decision in the matter by filing petitions for rehearing no later than
September 24, 2008. EPA will consider, in light of further developments in these cases, how the court decisions, as
well as laws and regulations issued independently by states, may affect future installations of FGD scrubber systems
as it continues reviewing the steam electric industry.	
                                             3-14

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       Table 3-4. Projected Future Use of FGD Systems at Coal-Fired Power Plants

Wet Scrubbed a
Dry Scrubbed a
Total Scrubbed a
Total Coal-Fired Generating
Capacity a
Percent Wet Scrubbed
Percent Scrubbed
2009
Capacity
(MW)
136,000
21,000
157,000
316,000
43%
50%
2010
Capacity
(MW)
162,000
21,500
184,000
318,000
51%
58%
2015
Capacity
(MW)
189,000
30,100
219,000
333,000
57%
66%
2020
Capacity
(MW)
231,000
36,700
268,000
371,000
62%
72%
2025
Capacity
(MW)
282,000
38,600
321,000
409,000
69%
78%
Source: [ERG, 2008d]
a - The capacities presented have been rounded to three significant figures. Due to rounding, the total capacity may
not equal the sum of the individual capacities. The 2009 capacities are from the NEEDS 2006 database which
preferentially uses summer and winter capacity before nameplate capacity. The 2010 - 2025 capacities presented in
this table are from estimates based on the IPM model [U.S. EPA, 2006a], which uses the NEEDS 2006 database
[U.S. EPA, 2006c] as a starting point. Because the nameplate capacities are not used in these projections, caution
should be used when comparing the capacities in this table to Table 3-1.

       Figure 3-5 presents the coal-fired plants currently (as  of June 2008) operating wet FGD
scrubber systems. Figure 3-6 present the coal-fired plants projected to be operating wet FGD
scrubber systems in 2020. The capacities represented in Figures 3-5 and 3-6 are for the plant-
level wet scrubbed capacity  and do not represent the total coal-fired or total generating capacity
at the plant. The coal-fired plants with FGD systems are heavily concentrated in the eastern
United States due to use of higher sulfur coal (e.g., eastern bituminous).  Figures 3-5 and 3-6,
also show that the number of plants operating wet FGD scrubbers is expected to increase
significantly,  as is the wet scrubbed capacity.
                                             3-15

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry


   Legend

   Plant Wet Scrubbed Capacity (Current)

    •  Less lhan 500 MW

    O  500-1.000 MW

    O  Greater than 1,000 MW

Source: [ERG, 2008a], [ERG, 2008f|
Note: The capacities in the figure represent the plant-level wet scrubbed capacity for the entire plant; they do not
represent the plant's total coal-fired or total generating capacity.  The capacities for the EIA-767 data represent the
reported nameplate capacity. The capacities for the UWAG-provided data, data request information, and site visit
and sampling information are based on information provided to EPA and may represent various capacities (e.g.,
nameplate capacity, net summer capacity, gross winter capacity).

     Figure 3-5. Coal-Fired Power Plants Operating Wet FGD Scrubber Systems, as of
                                              June 2008
                                                 3-16

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry

                     ••'
  Legend
  Plant Wet Scrubbed Capacity (2020)
    •   Less lhan 500 MW
    O   500-1.000 MW
    O  Greater than 1,000 MW

Source: [U.S. EPA, 2008b], [ERG, 2008f|
Note: The capacities in the figure represent the plant-level wet scrubbed capacity for the entire plant; they do not
represent the plant's total coal-fired or total generating capacity. The projected capacities presented are from
estimates based on the IPM model. The IPM model uses a variety of capacities in its estimates, but preferentially
uses summer and winter capacity before nameplate capacity.

 Figure 3-6.  Coal-Fired Power Plants Projected to be Operating Wet FGD Systems in 2020

3.1.3  FGD Wastewater Characteristics

       This section discusses the characteristics of FGD wastewaters based on information EPA
has collected thus far in the study.  Section 3.1.1 describes how the FGD wastewaters are
generated, while this section discusses what constituents may be present in the wastewater and
flow rate information. Pollutant  concentration data are presented for samples collected  during
the EPA wastewater sampling program, as are flow rate data from EPA's site visit and sampling
program and responses to EPA's data request.  See Chapter 2 for a description of EPA's data
collection activities.

       As described in Section 3.1.1 and Figure 3-1, the FGD scrubber blowdown (i.e., the
slurry stream exiting the FGD scrubber which is not immediately recycled) is typically
intermittently transferred from the FGD scrubber to the solids separation process.  As a  result,
the FGD scrubber purge (the waste stream from the FGD scrubber system that is transferred to a

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
wastewater treatment system or discharged) typically is also intermittent. The characteristics and
flow rate of the FGD scrubber purge wastewater depend upon the type of coal, the type of
scrubber, and the type of slurry dewatering process used at the plant, as well as the plant's
scrubber operating practices.

       Table 3-5 summarizes the FGD scrubber purge flow rates reported in the data request
responses and collected during EPA's site visit and sampling program.  The normalized flow
rates are based on the plants' scrubbed capacity, not the plants' total coal-fired or total generating
capacity. The 24 plants included in Table 3-5 operate a total of 51 wet FGD systems, which
scrub the flue gas from 57 coal-fired units. The average scrubbed capacity per plant is  1,280
MW and the median scrubbed capacity per plant is 1,270 MW. The scrubber purge flow rates
reported, including the normalized flow rates, vary significantly from plant to plant. Factors
contributing to this variance include the type of coal burned and its characteristics (e.g., chlorine
content), scrubber design,  and operating practices for the FGD system, such as chlorides
concentration/solids content set point and additive use.  Figures 3-7 and 3-8 presents the
distribution of the scrubber purge flow rates for the 24 plants included in Table 3-5. The average
gallons per day (GPD)/plant and GPD/Scrubbed MW scrubber purge flow rates are similar to the
FGD blowdown stream flow rates EPA observed when developing the effluent guidelines
promulgated in 1982 (671,000 GPD/plant and 811 GPD/MW) [U.S. EPA, 1982].

                        Table 3-5.  FGD Scrubber Purge Flow Rates

Number of Plants a
Average Flow
Rateb
Median Flow Rate b
Range of Flow
Rateb
Flow Rate per Plant
GPM/plant c
GPD/plant d
GPY/plant d
24
24
24
451
622,000
222,000,000
325
382,000
139,000,000
30.0-1,270
43,200 - 1,830,000
15,800,000 -
667,000,000
Normalized Flow Based on Scrubbed Capacity
GPM/Scrubbed MW c
GPD/Scrubbed MWd
GPY/ScrubbedMWd
24
24
24
0.494
681
238,000
0.210
297
108,000
0.0366-2.16
52.7-3,100
19,200-1,130,000
Source: Data request information [U.S. EPA, 2008a], and site visit and sampling information.
a - Sixteen plants reported operating wet FGD systems in the data request and 14 of the plants visited by EPA as
part of the site visit/sampling program operated wet FGD systems at the time of the visit. Two plants were included
in both data sets and are only included once in Table 3-5. Two plants from the data request are not included in this
summary because their wet FGD systems did not generate scrubber purge in 2006, one plant from the data request is
not included because it began operation of its wet FGD system in early 2007 and therefore, did not generate
scrubber purge in 2006, and one plant from the data request is not included because it only discharged scrubber
purge while testing emergency transfer pumps, which is required once per month.
b - The flow rates presented have been rounded to three significant figures.
c - The GPM flow rate represents the flow rate during the actual purge.
d - Because  some of the FGD scrubber purge flow rates are intermittent, GPD cannot be directly calculated from
GPM.  Similarly, some of the scrubber purge flows are not  generated 365 days per year, so GPY cannot be directly
calculated from GPD.
                                             3-18

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
Normalized Flow Rate (GPD/MW Scrubbed






Mill
	 iillllll















 Figure 3-7. FGD Scrubber Purge Flow Rate       Figure 3-8.  FGD Scrubber Purge
    Distributions from EPA Data Request      Normalized Flow Rate Distributions from
    Responses, Site Visits, and Sampling    EPA Data Request Responses, Site Visits, and
                                                              Sampling
Source: Data request information [U.S. EPA, 2008a], and site visit and sampling information.

       The pollutant concentrations in FGD scrubber purge vary from plant to plant depending
on the coal type, the sorbent used, the materials of construction in the FGD system, and the FGD
system operation. Generally, burning a higher sulfur coal will lead to a higher flow rate for the
scrubber blowdown and scrubber purge. Higher sulfur coals produce more sulfur dioxide in the
combustion process, which in turn increases the amount of sulfur dioxide removed in the
scrubber.  As a result, more solids are generated in the reaction in the scrubber, which increases
blowdown volumes.

       Likewise, a high chlorine coal can increase the volume and frequency of the scrubber
blowdown and scrubber purge. Many FGD systems are designed with materials resistant to
corrosion for specific chloride concentrations. A generating unit burning coal with higher
chlorine content will reach the  maximum allowable chloride concentration in the scrubber more
quickly, which will trigger the blowdown more frequently (and more importantly, the need to
purge FGD wastewater to prevent chloride  concentrations from exceeding allowable limits).

       The wastewater treatment system treating the FGD scrubber purge may also affect the
scrubber purge flow rate depending on whether it has any design constraints for particular
pollutants, such as chloride concentrations for a constructed wetland treatment system.
       Table 3-6 presents the pollutant concentrations representing the influent to the FGD
wastewater treatment systems for the four plants that EPA sampled with FGD wastewaters.9
fifth plant sampled by EPA is not included in Table 3-6 because it did not have an operating
FGD system at the time of sampling.
                                             The
       For the Big Bend sampling episode, EPA collected a grab sample of the influent to the
wastewater treatment system downstream of the equalization tank feeding the treatment system.
The equalization tank receives FGD scrubber purge from secondary hydroclones, off-
 Note that the influent-to-treatment sample obtained for a given plant does not necessarily represent the unaltered
scrubber purge, since the sample collected may include both scrubber purge and treatment system recirculation flow
streams.	
                                          3-19

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
specification effluent, backwash from sand filters, off-specification filter press filtrate, wash
water from polymer storage containers, and fume scrubber wastewater from the muriatic acid
tank.  During sampling, the plant transferred 154 gpm of off-specification filter press filtrate to
the equalization tank, which caused the plant to divert some of the FGD scrubber purge away
from the equalization tank; therefore, only 96 gpm of FGD scrubber purge was transferred to the
equalization tank during the sampling episode.  The total flow rate at the sampling point during
the sampling episode was 250 gpm, thus scrubber purge comprised only one-third of the total
influent-to-treatment flow sampled by EPA. The sampling episode report for Big Bend contains
more detailed information regarding the sample collection procedures [ERG, 2008m].

       For the Homer City sampling episode, EPA collected a grab sample of the influent to the
wastewater treatment system downstream of the equalization tank feeding the treatment system.
The equalization tank receives FGD scrubber purge from the secondary hydroclones and
backwash from sand filters. During sampling, the flow rate from the equalization tank to the
wastewater treatment system was 109 gpm. The sampling episode report for Homer City
contains more detailed information regarding the sample collection procedures [ERG, 2008J].

       Widows Creek operates once-though scrubbers (i.e., no recirculation of slurry within the
absorber), with the scrubber blowdown continuously sent to settling ponds.  For the Widows
Creek sampling episode, EPA collected a four-hour composite sample of the influent to the FGD
settling pond from a diked channel containing FGD scrubber blowdown from the two FGD
scrubbers. EPA collected the samples from the diked channel at a point downstream of the
influent to the channel to allow for some initial solids settling, but upstream of the inlet to the
FGD settling pond. At the time of the sampling, although one of the generating units operating a
FGD scrubber was shut down and therefore not sending flue gases through the scrubber, the
plant continued to transfer water  from the scrubber to the FGD settling pond. The flow rate
entering the FGD settling pond at the time of sampling was approximately 1,170 gpm, and plant
personnel estimated that approximately 390 gpm of the flow rate (one-third of the entire flow)
was from the FGD scrubber of the unit that was shut down. The sampling episode report for
Widows Creek contains more detailed information regarding the sample collection procedures
[ERG, 2008n].

       For the Mitchell sampling episode, EPA collected a grab sample of the FGD scrubber
purge transfer to the FGD wastewater treatment system.  The  sample collected contained only
FGD scrubber purge, which was transferred to the system at a flow rate of approximately  500
gpm.  The sampling episode report for Mitchell contains more detailed information regarding the
sample collection procedures [ERG, 2008k].

       Table 3-6 shows that FGD wastewater contains significant concentrations of chloride,
total dissolved  solids (TDS), nutrients, and metals, including bioaccumulative metals such as
arsenic, mercury, and selenium. Table 3-6  also shows that some of the pollutants are more likely
to be present in the particulate phase (e.g., aluminum, chromium, mercury), whereas other
pollutants are almost exclusively present in the dissolved phase (e.g., boron, magnesium,
manganese). The pollutant concentrations present in the FGD wastewater are large enough that
the waste stream typically requires some form of treatment prior to being discharged, at a
minimum to lower the total suspended solids (TSS) concentrations to meet the 30 mg/L (30-day
average) ELG limit for low-volume wastewaters (see Section 3.1.4 for more details).

                                         3^20

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     2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                               Table 3-6. Influent to FGD Wastewater Treatment System Concentrations
Analyte
Method
Unit
Big Bend -
Influent to FGD
Wastewater Treatment a
Homer City -
Influent to FGD
Wastewater Treatment a
Widows Creek -
FGD Scrubber
Slowdown a
Mitchell -
FGD Scrubber
Purge a
Routine Metals - Total
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
Zinc
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
31,200
62.5
75.5
1,590
12.9
626,000
224
6,690,000
757
172
120
23,500
69.1
4,830,000
21,900
ND (10.0)
618
2,090
4,150
2,530,000
ND (10.0)
420
724
245
1,540
289,000
86.4
1,590
11,900 R
28.8
224,000
150
3,220,000
1,400
369
811
824,000
340
2,760,000
225,000
243
375
2,560 R
4,000 R
1,430,000
Exclude
1,300 R
766
586
1,900
234,000
ND (86.9)
523
7,200
44.3
28,900
89.2
5,990,000
1,360
ND (217)
653
299,000
436
321,000
2,780
26.5
1,340
489
652
104,000
ND (43.4)
8,180
1,580
217
3,140
17,900
28.7
72.5
588
8.04
229,000
19.7
3,030,000
70.7
68.0
164
60,600
103
1,470,000
28,800
67.5
65.0
554
2,130
314,000
ND (10.0)
377
203
64.9
885
to

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     2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                               Table 3-6. Influent to FGD Wastewater Treatment System Concentrations
Analyte
Method
Unit
Big Bend -
Influent to FGD
Wastewater Treatment a
Homer City -
Influent to FGD
Wastewater Treatment a
Widows Creek -
FGD Scrubber
Slowdown a
Mitchell -
FGD Scrubber
Purge a
Routine Metals - Dissolved
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Hexavalent Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
Zinc
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
D 1687-92
200.7
200.7
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
ND (50.0)
33.9
18.6
1,820
ND (5.00)
618,000
179
4,470,000
ND (10.0)
24.0
ND (50.0)
27.2
ND (100)
ND (50.0)
4,110,000
9,610
ND (10.0)
581
851
3,610
1,970,000
14.3
12.5
108
ND (5.00)
16.8
ND (50.0)
ND (20.0)
ND (10.0)
149 R
10.5
254,000
26.2
1,990,000
ND (10.0)
ND (2.00)
201
14.5
ND (100)
ND (50.0)
3,100,000
173,000
ND (10.0)
30.6
1,350
656 R
1,440,000
61.2
ND (10.0)
ND (20.0)
6.28
ND (10.0)
86.6
ND (20.0)
13.9
257
ND (5.00)
24,100
ND (5.00)
849,000
18.7
ND (2.00)
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
176,000
583
ND (2.00)
876
ND (50.0)
366
76,700
14.3
ND (10.0)
ND (20.0)
ND (5.00)
ND (10.0)
ND (50.0)
ND (20.0)
ND (10.0)
488
6.02
232,000
ND (5.00)
2,350,000
ND (10.0)
5.00
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
1,370,000
27,900
ND (10.0)
22.2
355
46.9
324,000
ND (10.0)
ND (10.0)
ND (20.0)
ND (5.00)
87.8
to
to

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     2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                               Table 3-6. Influent to FGD Wastewater Treatment System Concentrations
Analyte
Method
Unit
Big Bend -
Influent to FGD
Wastewater Treatment a
Homer City -
Influent to FGD
Wastewater Treatment a
Widows Creek -
FGD Scrubber
Slowdown a
Mitchell -
FGD Scrubber
Purge a
Low-Level Metals - Total
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
24.9
165
238
651 L
103
69.9
16.4
2,570
3,470
39.8
1,870
31.1
1,220
52.8 R
1,270
747
351
533
2,840
3,530
37.3
2,130
51.8
617
86.0
1,380
826
545
24.7
634
651
93.8
2,720
9.23
59.9
5.28
176 L
139
68.1
138
650
1,990
6.33
730
Low-Level Metals - Dissolved
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
21.9
137
190
ND (160)
ND (40.0)
ND (10.0)
0.206
1,030
3,280
39.4
ND (100)
ND (0.400)
24.2 R
24.5
ND (16.0)
11.3
ND (1.00)
0.0809
1,450
584
23.2
34.7
8.90
18.0
3.16
ND (16.0)
ND (4.00)
ND (1.00)
0.0761
29.6
325
22.5
ND (10.0)
1.97
20.2
ND (1.00)
ND (80.0)
ND (20.0)
ND (0.500)
0.0111
433
443
4.47
160
Classicals
Ammonia As Nitrogen (NH3-N)
Nitrate/Nitrite (NO3-N + NO2-N)
4500-NH3F
353.2
MG/L
MG/L
31.5
NA
4.12
54.5
2.26
1.00
1.89
20.6
to

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      2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                                  Table 3-6. Influent to FGD Wastewater Treatment System Concentrations
Analyte
Total Kjeldahl Nitrogen (TKN)
Biochemical Oxygen Demand
(BOD)
Chloride
Hexane Extractable Material
(HEM)
Silica Gel Treated HEM (SGT-
HEM)
Sulfate
Total Dissolved Solids (TDS)
Total Phosphorus
Total Suspended Solids (TSS)
Method
4500-N,C
5210B
4500-CL-C
1664A
1664A
D5 16-90
2540 C
365.3
2540 D
Unit
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
Big Bend -
Influent to FGD
Wastewater Treatment a
51.6
1,370
24,200
ND (6.00)
NA
3,590
44,600
0.990
4,970
Homer City -
Influent to FGD
Wastewater Treatment a
14.2
ND (120)
11,800
ND (5.00)
NA
6,920
23,200
2.64
13,300
Widows Creek -
FGD Scrubber
Slowdown a
22.3
172
832
22.0
6.00 E
11,900
4,740
10.5
25,300 E
Mitchell -
FGD Scrubber
Purge a
13.3
21.0
7,200
11.0
ND (5.00)
1,640
18,100
3.57
7,320
to
      Source: [ERG, 2008J], [ERG, 2008k], [ERG, 2008m], [ERG, 2008n]
      a - The concentrations presented have been rounded to three significant figures.
      E - Sample analyzed outside holding time.
      L - Sample result between 5x and lOx blank result.
      R - MS/MSD % Recovery outside method acceptance criteria.
      Exclude - Results were excluded because the MS/MSD samples had a zero percent recovery.
      NA - Not analyzed.
      ND - Not detected (number in parenthesis is the report limit).  The sampling episode reports for each of the individual plants contains additional sampling
      information, including analytical results for analytes measured above the detection limit, but below the reporting limit (i.e., J-values).

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       Table 3-7 presents the pollutant concentrations representing the effluent from the FGD
wastewater treatment systems for the four plants that EPA sampled with FGD wastewater
treatment systems.  The fifth plant sampled by EPA is not included in Table 3-7 because it did
not have an operating FGD system at the time of sampling.

       The Big Bend FGD wastewater treatment system consists of an equalization tank
followed by a chemical precipitation system to reduce dissolved metals using lime for hydroxide
precipitation and ferric chloride for iron co-precipitation.  The plant then adds a flocculating
polymer to the wastewater and transfers it to a clarifier to remove the solids.  The overflow from
the clarifiers is filtered using sand gravity filters, transferred to a final holding tank, and then
discharged. EPA collected a grab sample of the effluent from the FGD wastewater treatment
system after the final holding tank. The average flow rate of the effluent from the FGD
wastewater treatment system during the sampling episode was 104 gpm. The sampling episode
report for Big Bend contains more detailed information regarding the sample collection
procedures [ERG, 2008m].

       The Homer City FGD wastewater treatment system consists of an equalization tank
followed by a chemical precipitation system to reduce dissolved metals using lime for hydroxide
precipitation, ferric chloride for iron co-precipitation, and a clarifier for solids removal. The
FGD wastewater is sent through a first stage of lime and ferric chloride precipitation followed by
a clarifier, and the wastewater is then treated in a second stage of lime and ferric chloride
precipitation followed by a clarifier. After the second clarifier, the wastewater is transferred to
an aerobic biological treatment system designed  for the removal of BOD.  After the biological
system, the wastewater is filtered, transferred to a final holding tank, and discharged. EPA
collected a grab sample of the effluent from the FGD wastewater treatment system directly from
the final holding tank.  The average flow rate of the effluent from the final holding tank during
the sampling episode was  approximately 107 gpm.  The sampling episode  report for Homer City
contains more detailed information regarding the sample collection procedures [ERG, 2008J].

       The Widows Creek FGD wastewater treatment system is a pond system that consisted of
three settling ponds at the  time of sampling; however, during the two site visits prior to the
sampling episode, the plant was operating four settling ponds. The FGD scrubber blowdown is
pumped to the inlet channels of the pond system  which direct the wastewater to the first FGD
settling pond. The  overflow from the first FGD settling pond is transferred to a second FGD
settling pond and then to a final FGD settling pond. The overflow from the final settling pond is
then discharged from the plant. EPA collected a grab sample of the effluent from the FGD
wastewater treatment system from the FGD wastewater discharge stream of the third settling
pond. EPA estimated that the effluent flow rate from the  treatment system was equal to the
influent to the treatment system, which was estimated to be 1,170 gpm.  The  sampling  episode
report for Widows Creek contains more detailed  information regarding the sample collection
procedures [ERG, 2008n].

       The Mitchell FGD wastewater treatment  system consists of a chemical precipitation
system to reduce dissolved metals using lime for hydroxide precipitation followed by a clarifier
for solids removal.  The overflow from the clarifier is transferred to an equalization tank, where
treated effluent is recycled by the plant when the system is not discharging. After the
equalization tank, the plant uses ferric chloride for  iron co-precipitation and then adds an anionic
polymer and transfers the wastewater to a second clarifier. The overflow from the second
                                         3^25

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     2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                             Table 3-7. Effluent from FGD Wastewater Treatment Systems Concentration
Analyte
Method
Unit
Big Bend -
Effluent from FGD
Wastewater
Treatment a' b
Homer City -
Effluent from FGD
Wastewater
Treatment a' b
Widows Creek -
Effluent from FGD
Pond System a'b
Mitchell -
Effluent from FGD
Wastewater
Treatment a'b
Routine Metals - Total
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
Zinc
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
ND (50.0)
22.1 R
ND (10.0)
1,490
ND (5.00)
369,000
24.9
4,420,000
ND (10.0)
ND (50.0)
<10.3
ND (100)
ND (50.0)
2,510,000
60.1
ND (10.0)
450 R
221
2,910 R
1,590,000
16.8
13.5
ND (20.0)
ND (5.00)
ND (10.0)
ND (50.0)
<20.8
ND (10.0)
71.3 R
7.68
191,000
ND (5.00)
2,000,000
ND (10.0)
ND (50.0)
12.5
<117
ND (50.0)
2,610,000
30,100
ND (10.0)
37.6
ND (50.0)
771
1,280,000
ND (10.0)
ND (10.0)
ND (20.0)
ND (5.00)
ND (10.0)
111
ND (20.0)
49.5
179
ND (5.00)
31,500
ND (5.00)
987,000
ND (10.0)
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
189,000
623
ND (2.00)
1,500
ND (50.0)
236
69,500
ND (10.0)
ND (10.0)
42.1
ND (5.00)
ND (10.0)
ND (50.0)
ND (20.0)
<10.3
433
ND (5.00)
208,000
ND (5.00)
2,380,000
ND (10.0)
ND (50.0)
16.2
318
ND (50.0)
1,280,000
4,440
ND (10.0)
22.9
ND (50.0)
83.6 R
305,000
ND (10.0)
<10.1
ND (20.0)
ND (5.00)
25.4
to

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     2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                             Table 3-7. Effluent from FGD Wastewater Treatment Systems Concentration
Analyte
Method
Unit
Big Bend -
Effluent from FGD
Wastewater
Treatment a' b
Homer City -
Effluent from FGD
Wastewater
Treatment a' b
Widows Creek -
Effluent from FGD
Pond System a'b
Mitchell -
Effluent from FGD
Wastewater
Treatment a'b
Routine Metals - Dissolved
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Hexavalent Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
D 1687-92
200.7
200.7
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
ND (50.0)
20.8 T
10.8 R,T
1,410
ND (5.00)
397,000
19.3
5,210,000
ND (10.0)
ND (2.00)
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
2,930,000
55.6
ND (10.0)
430 T
210
2,860 R
1,880,000
12.5
13.7
ND (20.0)
ND (5.00)
ND (50.0)
ND (20.0)
ND (10.0)
70.6 R,T
7.71
184,000
ND (5.00)
1,930,000
ND (10.0)
ND (2.00)
ND (50.0)
11.8
166 R
ND (50.0)
2,510,000
29,100
ND (10.0)
35.8
ND (50.0)
741 R
1,230,000
ND (10.0)
ND (10.0)
ND (20.0)
ND (5.00)
ND (50.0)
ND (20.0)
46.7
191
ND (5.00)
29,200
ND (5.00)
932,000
ND (10.0)
ND (2.00)
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
184,000
543 R
ND (2.00)
1,470
ND (50.0)
226
66,200
ND (10.0)
ND (10.0)
40.0
ND (5.00)
ND (50.0)
ND (20.0)
ND (10.0)
389
ND (5.00)
199,000
ND (5.00)
2,270,000
ND (10.0)
11.0
ND (50.0)
14.1
ND (100)
ND (50.0)
1,220,000
4,120
ND (10.0)
21.4
ND (50.0)
71.7
300,000
ND (10.0)
ND (10.0)
ND (20.0)
ND (5.00)
to

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     2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                             Table 3-7.  Effluent from FGD Wastewater Treatment Systems Concentration
Analyte
Zinc
Method
200.7
Unit
UG/L
Big Bend -
Effluent from FGD
Wastewater
Treatment a' b
ND (10.0)
Homer City -
Effluent from FGD
Wastewater
Treatment a' b
ND (10.0)
Widows Creek -
Effluent from FGD
Pond System a'b
ND (10.0)
Mitchell -
Effluent from FGD
Wastewater
Treatment a'b
ND (10.0)
Low-Level Metals - Total
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
14.2
68.0
25.8
ND (80.0)
ND (20.0)
ND (5.00)
0.156
381
2,500
31.1
ND (50.0)
ND (0.400)
23.0
ND (2.00)
ND (16.0)
9.67
ND (1.00)
0.117
92.1
613
16.0
15.2
11.8
47.6
3.73
ND (16.0)
ND (4.00)
ND (1.00)
0.0438
36.2
208
11.1
ND (10.0)
<1.37
<25.2
ND (3.00)
ND (120)
ND (30.0)
ND (1.50)
0.788
<155
431 T
3.96
<83.5
Low-Level Metals - Dissolved
Antimony
Arsenic
Cadmium
Chromium
Hexavalent Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1636
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
13.7
72.4
22.2
ND (80.0)
ND (5.00)
ND (20.0)
ND (5.00)
0.0688
396
2,560
31.5
ND (50.0)
ND (0.400)
22.5
ND (2.00)
ND (16.0)
ND (2.50)
9.39
ND (1.00)
0.0542
93.5
620
15.8
15.7
11.9
46.5
3.74
ND (16.0)
3.20
ND (4.00)
ND (1.00)
0.0107
33.3 L
293
11.0
ND (10.0)
1.64
20.9 T
ND (1.00)
ND (80.0)
ND (2.50)
ND (20.0)
ND (0.500)
0.159
102
407
3.99
ND (50.0)
to
oo

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      2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                                 Table 3-7. Effluent from FGD Wastewater Treatment Systems Concentration
Analyte
Method
Unit
Big Bend -
Effluent from FGD
Wastewater
Treatment a' b
Homer City -
Effluent from FGD
Wastewater
Treatment a' b
Widows Creek -
Effluent from FGD
Pond System a'b
Mitchell -
Effluent from FGD
Wastewater
Treatment a'b
Classical*
Ammonia As Nitrogen (NH3-N)
Nitrate/Nitrite (NO3-N + NO2-N)
Total Kjeldahl Nitrogen (TKN)
Biochemical Oxygen Demand
(BOD)
Chloride
Hexane Extractable Material
(HEM)
Silica Gel Treated HEM (SGT-
HEM)
Sulfate
Total Dissolved Solids (TDS)
Total Phosphorus
Total Suspended Solids (TSS)
4500-NH3F
353.2
4500-N,C
5210B
4500-CL-C
1664A
1664A
D5 16-90
2540 C
365.3
2540 D
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
24.1
NA
98.7
> 1,720
22,500
6.00
ND (6.00)
1,920
40,600
0.355
31.5
0.295
36.5 R
3.04
ND (120)
11,800
ND (5.00)
NA
2,790
22,600
0.520
<5.50
0.220
0.0945
2.51
<10.0
1,120
ND (5.00)
NA
2,060
5,830
0.0115 E
8.00 E
3.49
25.4
9.74
<7.50
6,700
5.00
ND (4.00)
1,770
17,700
0.0745
17.5
to
VO
      Source: [ERG, 2008J], [ERG, 2008k], [ERG, 2008m], [ERG, 2008n]
      a - The FGD effluent results represent the average of the FGD effluent and the duplicate of the FGD effluent analytical measurements.
      b - The concentrations presented have been rounded to three significant figures.
      < - Average result includes at least one non-detect value. (Calculation uses the report limit for non-detected results).
      > - Result above measurement range.
      E - Sample analyzed outside holding time.
      L - Sample result between 5x and lOx blank result.
      R - MS/MSD % Recovery outside method acceptance criteria.
      T - MS/MSD RPD outside method acceptance criteria.
      NA - Not analyzed.
      ND - Not detected (number in parenthesis is the report limit). The sampling episode reports for each of the individual plants contains additional sampling
      information, including analytical results for analytes measured above the detection limit, but below the reporting limit (i.e., J-values).

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
clarifier is transferred to a final holding tank and either transferred to the bottom ash pond and
eventually discharged or recycled back to the equalization tank. EPA collected a grab sample of
the effluent from the FGD wastewater treatment system from the discharge line of the final
holding tank. The average flow rate from the effluent of the FGD wastewater treatment system
during the sampling episode was 541 gpm.  The sampling episode report for Mitchell contains
more detailed information regarding the sample collection procedures [ERG, 2008k].

       Table 3-7 shows that treated FGD wastewater from these systems contains significant
concentrations of chlorides, TDS, and some metals, including selenium (a bioaccumulative
metal). Most metals still present in the treated FGD wastewater are predominantly in the
dissolved phase.

3.1.4  FGD Wastewater Treatment

       EPA's 2007/2008 detailed study has largely centered on FGD wastewater generated at
coal-fired power plants. Sections 3.1.1 and 3.1.3 describe the generation and characteristics of
FGD wastewater.  This section discusses the various treatment systems available to treat FGD
wastewater,  as well as treatment technologies that are currently under investigation. The
treatment systems and technologies that EPA has identified during this detailed study include the
following:

       •       Settling ponds;
       •       Chemical precipitation (using hydroxide and/or sulfide);
       •       Biological treatment;
       •       Constructed wetlands;
       •       Zero-liquid discharge; and
       •       Other technologies under investigation.

       Based on information EPA collected throughout the detailed study, most of the plants
discharging FGD wastewater use pond-based approaches; however, there are indications that the
use of more  advanced wastewater treatment systems is increasing.

       Table 3-8 presents information on the FGD wastewater treatment systems currently
operating at  plants included in EPA's data set.  Information is provided for 82 out of the 107
plants (77 percent) operating wet FGD scrubber systems as of June 2008, representing 166 out of
the 222 wet-scrubbed coal-fired generating units (75 percent).  Of these 82 plants, 30 plants (37
percent) do not discharge any FGD wastewater, and another plant achieves zero discharge of the
FGD wastewater from several of its wet scrubbers.  These plants are able to achieve "zero
discharge" by either recycling all FGD wastewater back to the  scrubber (27 plants), using
evaporation  ponds (3 plants), or mixing the FGD wastewater with dry fly ash (one plant).

       Fifty-two of the 82 plants currently operating wet FGD scrubbers discharge the FGD
wastewater.  Of these 52 plants, 31 plants (38 percent of the total; 60 percent of the  discharging
plants) treat  the wastewater using a settling pond, 15 plants (18 percent of the total;  29 percent of
the discharging plants) rely on more advanced treatment such as chemical precipitation or
biological treatment, two plants use constructed wetlands treatment systems as the primary
treatment mechanism, and four plants commingle the FGD wastewater with other waste streams
                                          3-30

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                  Table 3-8. FGD Wastewater Treatment Systems Identified During EPA's Detailed Study

Total
Settling Ponds
Combined FGD and Ash Ponds (FGD solids
removal prior) e> f
Combined FGD and Ash Ponds (No FGD
solids removal prior) e> g
FGD Ponds (FGD solids removal prior) f> h
FGD Ponds (No FGD solids removal prior) g'h
Chemical Precipitation ("Chem Precip")
Chem Precip (type unknown)
Hydroxide Chem Precip
Hydroxide and Sulfide Chem Precip
Combination Settling Pond and Chem Precip
Tank-Based Biological
Anoxic/Anaerobic Biological (designed for
metals & nitrogen removal)
Wet FGD Systems in the Combined Data
Set Currently Operating as of June 2008 a
Number of
Plants with
FGD
Wastewater
Treatment
Systems
82
31
19
2
4
6
11
—
8
1
2
1
1
Number of
Generating
Units Serviced
by FGD
Wastewater
Treatment
Systems
166
64
43
o
5
8
10
20
—
15
2
o
3
3
o
5
Wet
Scrubbed
Capacity c
(MW)
84,100
26,700
15,000
1,070
3,540
7,110
10,400
—
8,330
1,230
803
2,150
2,150
Wet FGD Systems in the Combined Data Set
Expected to Begin Operating After June 2008 b
Number of
Additional Plants
Expected to
Install FGD
Wastewater
Treatment
Systems c
9
2
0
—
1
1
5
1
2
2
—
1
1
Number of
Additional
Generating Units
Expected to be
Serviced by FGD
Wastewater
Treatment Systems c
32
12
1
—
5
6
13
1
7
5
—
2
2
Wet
Scrubbed
Capacity d
(MW)
18,700
8,810
750
—
4,040
4,020
7,580
562
4,200
2,820
—
1,150
1,150

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      2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                        Table 3-8. FGD Wastewater Treatment Systems Identified During EPA's Detailed Study

Combination Chem Precip and Tank-Based
Biological
Chem Precip and Anoxic/ Anaerobic
Biological (designed for metals & nitrogen
removal)
Chem Precip and Aerobic Biological
(designed for BOD5 removal)
Chem Precip, Anoxic/ Anaerobic Biological
(designed for metals & nitrogen removal), and
CWTS
Zero Discharge
Zero Discharge: Recycle All FGD Water
Zero Discharge: Evaporation Pond
Zero Discharge: Conditioning Dry Fly Ash
Wet FGD Systems in the Combined Data
Set Currently Operating as of June 2008 a
Number of
Plants with
FGD
Wastewater
Treatment
Systems
3

2
1
31
27
3
1
Number of
Generating
Units Serviced
by FGD
Wastewater
Treatment
Systems
5

3
2
60
55
4
1
Wet
Scrubbed
Capacity c
(MW)
4,800

2,400
2,400
34,600
32,100
1,880
600
Wet FGD Systems in the Combined Data Set
Expected to Begin Operating After June 2008 b
Number of
Additional Plants
Expected to
Install FGD
Wastewater
Treatment
Systems c
1
1
—

—
—
—
—
Number of
Additional
Generating Units
Expected to be
Serviced by FGD
Wastewater
Treatment Systems c
5
5
—

—
—
—
—
Wet
Scrubbed
Capacity d
(MW)
1,140
1,140
—

—
—
—
—
to

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                     Table 3-8.  FGD Wastewater Treatment Systems Identified During EPA's Detailed Study

Other Handling
CWTS
Commingled with other Wastewater
Wet FGD Systems in the Combined Data
Set Currently Operating as of June 2008 a
Number of
Plants with
FGD
Wastewater
Treatment
Systems
6
2
4
Number of
Generating
Units Serviced
by FGD
Wastewater
Treatment
Systems
14
6
8
Wet
Scrubbed
Capacity c
(MW)
5,410
2,480
2,920
Wet FGD Systems in the Combined Data Set
Expected to Begin Operating After June 2008 b
Number of
Additional Plants
Expected to
Install FGD
Wastewater
Treatment
Systems c
—
—
—
Number of
Additional
Generating Units
Expected to be
Serviced by FGD
Wastewater
Treatment Systems c
—
—
—
Wet
Scrubbed
Capacity d
(MW)
—
—
—
a - Source: UWAG-provided data [ERG, 2008f], data request information [U.S. EPA, 2008a], and site visit and sampling information. Includes treatment
systems servicing units identified in the "combined data set" with wet FGD systems operating as of June 2008, and systems in the "combined data set" that will
startup after June 2008.  Units from the "combined data set" that were identified solely from the EIA-767 data are not included in the table because the FGD
wastewater treatment system information for those units is unavailable.  The data set shown in this table represents 82 of the 107 plants (77 percent), 166 of the
222 generating units (75 percent),  and 81 percent of the wet scrubbed capacity for currently operating wet FGD systems (as of June 2008). The 9 plants that will
install new FGD wastewater treatment systems after June 2008 represent only a fraction of future wet FGD installations.
b - Source: Data request information [U.S. EPA, 2008a] and site visit and sampling information. Includes only treatment systems servicing units identified in the
"combined data set" with planned wet FGD systems expected to begin operating after June 2008. It does not represent all wet FGD systems that will begin
operating after June 2008.
c - 25 of the 32 additional generating units will be serviced by new FGD wastewater treatment systems that will be installed at 9 plants. The remaining 7 of the
32 additional generating units will be serviced by existing FGD  wastewater treatment systems; therefore, the plant is not included in the count of "Additional
Plants Expected to Install FGD Wastewater Treatment Systems."
d - The capacities presented have been rounded to three significant figures. Due to rounding, the total capacity may not equal the sum of the individual
capacities. The capacities for the UWAG-provided data, data request information, and site visit and sampling information are based on information provided to
EPA and may represent various capacities (e.g., nameplate capacity, net summer capacity, gross winter capacity). In addition, for some facilities included in the
data request, the capacities reported in the UWAG-provided data differed from the capacities reported in the data request.
e - The combined FGD and ash pond system refers to a settling pond that handles untreated FGD scrubber purge and ash wastewaters (either bottom ash or fly
ash sluice). Some plants transferred treated FGD wastewaters to the ash pond for dilution prior to discharge, but these systems are not reflected in this table.
f - "FGD Solids removal prior" means that gypsum or calcium sulfite sludge was removed prior to treatment.
g - "No FGD Solids removal prior" means that gypsum or calcium sulfite sludge was sent to the settling pond.
h - The FGD pond  system refers to settling ponds that handle untreated FGD scrubber purge, but do not handle ash wastewaters. The FGD pond may handle
other wastewaters along with the FGD scrubber purge, such as low-volume wastes, but the pond cannot receive ash wastewaters to be considered an FGD pond.

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
(other than ash sluice water). Note that many plants commingle the FGD waste stream with
other wastewater streams following the management practice shown in Table 3-8.

       Table 3-8 also presents information for the type of treatment systems that will be used
treat wastewater from new FGD scrubbers that will begin operating in the next few years, using
information reported by the companies responding to EPA's data request. Data are provided for
nine plants that do not currently operate FGD wastewater treatment systems, and thus will be
installing new treatment systems as scrubbers are installed.  Despite recent interest in the use of
more advanced wastewater treatment systems, the data indicate that the use of pond systems may
continue to be significant, particularly at the plants that have pre-existing ponds.

       EPA investigated whether there is a relationship between FGD system age and the type of
treatment system used.  Wastewater from FGD systems that came online in the 1970s, 1980s,
and early 1990s is typically treated in pond systems or recycled. In a couple of cases,
wastewater from FGD systems that came on line in the mid-1980s is treated with hydroxide
chemical precipitation systems. Most of the more advanced wastewater treatment systems are
associated with plants that installed FGD  scrubbers in the last decade. However, the move
toward advanced treatment systems is not universal and some plants have reported that they
intend to use existing or new settling ponds to treat the wastewater from new scrubbers.

       The following sections discuss individual FGD wastewater treatment systems and
technologies. For some of the technologies that are under investigation, such as those discussed
in Section 3.1.4.6, EPA has only limited information at this time.

       3.1.4.1    Settling Ponds

       Settling ponds are designed to remove particulates from wastewater by means of gravity.
To accomplish this, the  wastewater must reside in the pond long enough for removal of the
desired particle size.  The size and configuration of settling ponds vary by plant; some settling
ponds operate as a system of several ponds, while others consist of one large pond.  The ponds
are generally sized to provide a certain residence time to reduce the TSS  levels in the wastewater
and to allow for a certain life-span of the pond based on the rate of solids buildup within the
pond. Coal-fired power plants do not typically add treatment chemicals to settling ponds, other
than to adjust the pH of the wastewater before it exits the pond to bring it into compliance with
NPDES permit limits.

       Settling ponds can effectively reduce the amount of TSS in wastewater, as well as
specific pollutants that are in particulate form, provided that the settling pond has a sufficiently
long residence time; however, settling ponds are not designed to reduce the amount  of dissolved
metals.  Table 3-6, in Section 3.1.3, shows that the FGD wastewater entering a treatment system
contains significant concentrations of several pollutants in the dissolved phase of the wastewater,
including boron, manganese, and selenium. Therefore, these dissolved metals are likely
discharged if FGD wastewater is treated in settling ponds. Additionally, EPRI has reported that
adding FGD wastewater to ash ponds may reduce the  settling efficiency in the ash ponds, due to
gypsum particle dissolution, thus increasing the effluent TSS concentration [EPRI, 2006b].

       The pond systems used by power plants for treating FGD wastewater have the potential
to undergo seasonal  turnover effects, similar to other ponds and lakes that become thermally

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
stratified as a result of seasonal conditions.  During the summer, some temperate lakes may
become thermally stratified. When this occurs, the top layer of the lake is warmer and contains
higher levels of dissolved oxygen, whereas the bottom layer of the lake is colder and has
significantly lower levels of oxygen, often being anoxic.  Typically during fall, as the air
temperature decreases, the upper layer of the pond becomes cooler and more dense, then sinks
and causes the entire volume of the lake to circulate.  Solids that have settled at the bottom of the
pond could potentially become resuspended due to the mixing, leading to increased
concentrations of pollutants being discharged during the turnover period.  In addition, EPA
believes that anaerobic conditions at the bottom of the pond may promote the formation of
methylmercury, which could then be present in the  discharge.  Seasonal turnover effects are
largely dependent on the size and configuration of the pond or lake, and some ponds likely do
not experience turnover because they are too small  and shallow; however, some of the power
plant settling ponds are large and  deep (e.g., 340 acres, greater than 10 meters deep). EPA will
continue to investigate this phenomenon as it relates to pollutant discharges from coal-fired
power plants.

       As shown in Table 3-8, settling ponds are the most commonly used systems for managing
FGD wastewater within EPA's combined data set.  Sixty percent of the plants discharging FGD
wastewater use settling ponds  (31 of 52 plants),  and most of those plants transfer FGD scrubber
purge wastewater (or FGD scrubber blowdown) directly to a settling pond that also treats other
waste streams, specifically fly ash sluice and/or bottom ash sluice.  Ten of the 31 plants transfer
the FGD scrubber purge wastewater (or FGD scrubber blowdown) to a settling pond specifically
designated for the treatment of FGD wastewater. In these cases, the FGD wastewater pond
effluent is either discharged directly to surface waters or transferred to a commingled settling
pond for further settling and dilution.

       EPA has also identified two plants (one currently operating FGD system and one
planned) that transfer the FGD scrubber purge to a settling pond for initial solids removal and
then transfer the wastewater to a biological treatment system for further treatment.

       Most settling pond systems within EPA's combined data set are associated with wet FGD
systems that were installed prior to 2000.  More advanced treatment systems have received
increased attention in recent years; however, information compiled by EPA indicate that the use
of pond systems may continue to  be significant in the future, with some plants currently without
scrubbers announcing that they will rely on settling ponds to treat FGD wastewater.  Settling
ponds are also expected to be the  treatment system  of choice for wastewater from scrubbers that
will be installed at plants already  operating at least  one wet FGD system.

       3.1.4.2    Chemical Precipitation

       In a chemical precipitation wastewater treatment system, chemicals are added to the
wastewater to alter the physical state of dissolved and suspended solids to facilitate settling and
removal of the solids.  The specific chemical(s) used depends upon the type of pollutant
requiring removal. In the case of metals removal, lime (calcium hydroxide) is often added to
elevate the pH of the wastewater and facilitate the precipitation of metals into insoluble
hydroxides.  The calcium carbonate formed from the precipitation reaction acts as a coagulant
for the metal hydroxides.  A significant amount of lime is required for metals
precipitation/coagulation if it used alone, whereas less lime is required if used together with an

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
iron salt such as ferric chloride.  The ferric chloride acts as a coagulant, forming a dense floe that
enhances settling of the metals precipitate in downstream clarification stages. Additionally,
ferric chloride may coprecipitate some metals and organic matter.

       In chemical precipitation systems designed to treat FGD wastewater, sulfide chemicals
(e.g., trimercapto-s-triazine (TMT), Nalmetฎ, sodium sulfide) may be added to enhance the
precipitation and removal of heavy metals, such as mercury. While precipitation due to
hydroxide addition can remove some heavy metals, precipitation due to sulfide addition can
remove additional heavy metals because metal sulfides have lower solubilities than metal
hydroxides.  FGD wastewater chemical precipitation systems may include various configurations
of lime, ferric chloride, and sulfide addition stages, as well as clarification stages.

       The EPA site visit and sampling program has focused on chemical precipitation systems
currently in place to treat FGD wastewater. Of the 14 coal-fired power plants that EPA visited
that were operating FGD systems at the time of the visit, nine of the plants operate a chemical
precipitation system (either hydroxide or both hydroxide and sulfide) to treat the  FGD
wastewater.  Figure 3-9 presents a process flow diagram of a typical precipitation system
(hydroxide and sulfide addition) based on information EPA collected during site  visits.  Note that
a chemical precipitation system that does not include sulfide precipitation is similar to the system
shown in Figure 3-9, except that it would not include reaction tank 2, where the sulfide is added.

       In the chemical precipitation system shown in Figure 3-9, the FGD scrubber purge
wastewater from the plant's hydroclones  is transferred to an equalization tank, where the
intermittent flows from the hydroclones are equalized, allowing the plant to pump a constant
flow rate of FGD scrubber purge through the treatment system. The equalization tank also
receives wastewater from a filtrate sump, which includes water from the gravity filter backwash
and filter press filtrate.

       The FGD scrubber purge is transferred at a continuous flow from the equalization tank to
reaction tank 1, where the plant adds hydrated lime to raise the pH of the wastewater from
between 5.5 - 6.0 to between 8.0 - 10.5 to precipitate the soluble metals as insoluble hydroxides
and oxyhydroxides. The reaction tank also desaturates the remaining gypsum in  the wastewater,
which prevents gypsum scale formation in the downstream wastewater treatment equipment.

       From  reaction tank 1, the wastewater flows to reaction tank 2, where organosulfide (most
commonly TMT) is added. Plants either  operate the organosulfide precipitation step after the
hydroxide precipitation step, as shown in Figure 3-9, or before the hydroxide precipitation  step.
Additionally, some plants may operate a clarification step between the two precipitation steps.

       From  reaction tank 2, the wastewater flows to reaction tank 3, where ferric chloride is
added to the wastewater for coagulation.  The effluent from reaction tank 3 flows to the flash mix
tank, where polymer is added to the wastewater, prior to be being transferred to the clarifier.
Alternatively, the polymer can be added directly to the waste stream as it enters the clarifier.
The polymer is used to flocculate fine suspended particles in the wastewater.

       The clarifier settles the solids that were initially present in the FGD scrubber purge
stream as well as the additional solids (precipitate) that were formed during the chemical
precipitation steps. The overflow from the clarifier may be acidified with hydrochloric acid to
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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
  FGD Scrubber Purge
      Wastewater
                     Equalization
                        Tank
                                                    Lime
                                                                                   Organosulfide
o
Reactior
O
i Tank 1


•*
    Oko
   Reaction
    Tank 2
;
Sludge Holding
Tank

*•

I
'ilter Pre^
V ^

I


A
                                                                                                   I
                                                                                                   I      I
                                                                                                   I      I
                                                                                                  +    4-
                                               To Sludge Disposal
                                                                                                 Filtrate
                                                                                                 Sump
                                                                                                                 Ferric
                                                                                                               Chloride
 oka
Reaction
 TankS
                                                                                                                       Treated
                                                                                                                      Effluent to
                                                                                                                      Discharge
                                                                                                                     Treated
                                                                                                                     Effluent
                                                                                                                     Recycle
                 Figure 3-9. Process Flow Diagram for a Hydroxide and Sulfide Chemical Precipitation System

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
readjust the pH value to meet effluent limits. After acidification, the wastewater may flow
through a sand filter. The backwash from the sand filters is transferred to a filtrate sump and
recycled back to the equalization tank at the beginning of the treatment system.

       The treated FGD wastewater is collected in a wastewater holding tank and either
discharged directly to surface waters or, more commonly, commingled with other waste streams
prior to discharge.  As described in Section 3.1.1, plants do not normally recycle this treated
FGD wastewater within the FGD scrubber system because of the chlorides level.

       The sludge from the clarifier is transferred to the  sludge holding tanks using transfer
pumps. The sludge is then dewatered using a filter press. The cake generated from the filter
press is typically sent to an on-site landfill for disposal. The filter press filtrate is transferred to a
filtrate sump and recycled back to the equalization tank at the beginning of the treatment system.

       As shown in Table 3-8, 14 of the 52 currently discharging plants in EPA's combined data
set (27 percent) are operating a chemical precipitation system to treat FGD scrubber purge
wastewater.  Three of these 14 plants operate chemical precipitation systems that include a
sulfide precipitation step. The majority of the chemical precipitation systems were installed after
1995.

       3.1.4.3    Biological Treatment

       Biological wastewater treatment systems use microorganisms to consume biodegradable
soluble organic contaminants and bind much of the less soluble fractions into floe. Pollutants
may be reduced aerobically, anaerobically, and/or with the use of anoxic zones.  Based on the
information EPA has collected during the 2007/2008  detailed study, two main types of biological
treatment systems are currently used (or planned) to treat FGD wastewater: aerobic systems for
BODS removal; and anoxic/anaerobic systems for metals and nutrient removal.  These systems
can use fixed film or suspended growth bioreactors, and operate as conventional flow-through or
as sequencing batch reactors (SBR).  The subsections below discuss the wastewater treatment
processes for each of these biological treatment systems.  EPA has compiled information on two
aerobic systems and two anoxic/anaerobic systems operating as of June 2008, and five more
anoxic/anaerobic systems scheduled to begin operating over the next year. Indications are that
additional plants are considering installing biological treatment systems.

       Aerobic Biological Treatment

       An aerobic biological treatment system can effectively reduce BOD5  from wastewaters.
In a conventional flow-through design, the wastewater is continuously fed to the aerated
bioreactor.  The microorganisms in the reactor use the dissolved oxygen from the aeration to
digest the organic matter in the wastewater, thus reducing the BODs. The digestion of the
organic matter produces  sludge, and may be treated with a vacuum filter to better manage its
ultimate disposal. The treated wastewater from the system overflows out of the reactor.

       An SBR is a type of activated sludge treatment system that can reduce BODs and, when
operated to create anoxic zones under certain operating conditions, it can also achieve
nitrification and denitrification. Plants often operate at least two identical reactors that are
operated sequentially in batch mode. The treatment in each SBR consists of a four stage process:

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
fill, aeration and reaction, settling, and decant.  While one of the SBRs is settling and decanting,
the other SBR is filling, aerating, and reacting.

       When operated as an aerobic system, the SBR operates as follows.  The filling stage of
the SBR consists of transferring the FGD wastewater into the SBR that contains some activated
sludge from the previous reaction batch. During the aeration and reaction stage, the reactor is
aerated and the BODs is reduced as the microorganisms digest the organic matter in the
wastewater.  During the settling phase, the air is turned off, and the solids in the SBR are allowed
to settle to the bottom.  The wastewater is then  decanted off the top of the SBR and either
transferred to surface water for discharge or transferred for additional treatment. Additionally,
some of the  solids from the bottom of the SBR  are removed and transferred for processing, but
some of the  solids are retained in the SBR, leaving the microorganisms in the system.

       EPA has collected information from two coal-fired power plants  operating an aerobic
biological reactor as part of the FGD wastewater treatment system. In each case the biological
step follow chemical precipitation processes. One plant uses a conventional aerobic biological
system while the other operates as an aerobic SBR. Both of these plants use additives in their
FGD  scrubbers (DBA or formic acid), which increases the BOD5 concentration in the scrubber
purge wastewater.  These aerobic biological treatment systems were installed for the purpose of
reducing the BOD5 in the wastewater.

       Anoxic/Anaerobic Biological Treatment

       Some coal-fired power plants are moving towards the use of anoxic/anaerobic biological
systems to achieve better reductions of certain pollutants (e.g., selenium, mercury, nitrates) than
has been possible with other treatment processes employed at power plants.

       EPA has collected information on two plants currently operating  fixed-film
anoxic/anaerobic bioreactors and two additional plants that plan to operate similar fixed-film
bioreactors in the near future. These plants are  each operating (or planning  to operate) some
form  of pre-treatment upstream of the bioreactors, either chemical precipitation or settling ponds,
to reduce the wastewater TSS concentration entering the bioreactor.

       The fixed-film bioreactor consists of an activated carbon bed that is  inoculated with
microorganisms, which are tailored on a site-specific basis to reduce selenium and other metals.
Growth of the microorganisms within the activated carbon bed creates a  fixed-film that retains
the microorganisms and precipitated solids within the bioreactor. A molasses-based feed is
added to the wastewater prior to entering the bioreactor as a feed source  for the microorganisms.
[Pickett, 2006]

       The bioreactor is designed for plug flow, containing different zones  within the reactor
that have differing oxidation potential.  The top part of the bioreactor is more aerobic and allows
for nitrification and organic carbon oxidation. As the wastewater moves down through the
bioreactor, it enters an anoxic zone where denitrification occurs as well as reduction of both
selenate and selenite. [Pickett, 2006]

       As selenate and selenite are reduced within the bioreactor, elemental selenium forms
nanospheres that adhere to the cell walls of the  microorganisms. Because the microorganisms

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
are retained within the bioreactor by the activated carbon bed, the elemental selenium is
essentially fixed to activated carbon until it is removed from the system.  The bioreactor can also
reduce other metals within the system, including arsenic, cadmium, and mercury. [Pickett, 2006]

       Periodically, the bioreactor must be flushed to remove the solids and inorganic materials
that have accumulated within the bioreactor.  The flushing process involves fluidizing the
bioreactor by flowing water upward through the system, which dislodges the particles fixed
within the activated carbon.  The water and solids overflow from the top of the bioreactor and are
removed from the system.  This flush water must be treated prior to being discharged because of
the elevated levels of solids and selenium. [Pickett, 2006]

       Another system developed by a treatment system vendor is based on anoxic/anaerobic
biological treatment,  but relies on the use of suspended growth flow-through bioreactors instead
of fixed film bioreactors.  Nevertheless, both designs share the fundamental processes that lead
to denitrification and reduction of metals in anoxic and anaerobic environments. This suspended
growth bioreactor system is currently undergoing long-term pilot testing.

       The anoxic/anaerobic conditions described for the flow-through systems can also be
achieved using SBRs. The SBR operation would be similar to that described above for the
aerobic biological treatment system; however, to create anoxic conditions the aeration stage
would be followed by a period of air on, air off, which creates aerobic zones for nitrification and
anoxic zones  for denitrification, removing the nitrogen present in the wastewater.  EPA has
collected information on three coal-fired power plants that are planning to operate
anoxic/anaerobic biological SBRs, with startup  scheduled to occur by 2010. The SBR systems at
these plants are expected to be operated in combination with chemical precipitation systems,
with the overall systems designed to optimize reductions of metals and nitrogen compounds.

       3.1.4.4    Constructed Wetlands

       A constructed wetland treatment system is an engineered system that uses natural
biological processes involving wetland vegetation, soils, and microbial activity  to reduce the
concentrations of metals, nutrients,  and TSS in wastewater. A constructed wetland typically
consists of several cells that contain bacteria and vegetation (e.g., bulrush, cattails), which are
selected based on the specific pollutants targeted for removal.  The vegetation completely fills
each cell and  produces  organic matter (i.e., carbon) used by the bacteria.  The bacteria reduce
metals that are present in the aqueous phase of the wastewater, such as mercury and selenium, to
their elemental state.  The targeted metals are partitioned into the sediment and taken up by the
vegetation in  the wetland cells.   The wetland cells are contained above a nonpermeable liner.
[EPRI, 2006b; Rodgers, 2005]

       Constructed wetlands performance can be adversely affected by high temperature, COD,
nitrates, sulfates, boron, and chlorides in wastewater. Coal-fired power plants dilute FGD
wastewater with service water before it enters a constructed wetland to reduce the chlorides
concentration and temperature, which can damage the vegetation in the treatment cells.
Chlorides in a constructed wetlands treatment system typically must be maintained below 4,000
mg/L.  Most plants operate the FGD scrubber system to maintain chloride levels within in range
12,000-20,000 ppm.  As a result, plants operating constructed wetlands treatment systems will
need to dilute the FGD  wastewater prior to transferring it to the wetland.   EPA has observed that

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
plants operating the wetlands tend to operate the FGD system at the lower end of the chloride
range.  To accomplish this, the plants purge FGD wastewater from the system at a higher flow
rate than they otherwise would do if operating the FGD scrubber at a higher chloride level.

       Three coal-fired power plants currently operate a constructed wetland for treatment of
FGD wastewater. Two of these plants use the constructed wetlands as the main treatment system
for the targeted pollutants (i.e., mercury, selenium, nutrients, and TSS).  These plants operate a
solids removal system (i.e., clarifier) upstream of the CWTS. The third plant operates a
hydroxide and sulfide chemical precipitation system followed by a biological treatment system
upstream of the CWTS. In this case, the CWTS is used as a polishing step for metals removal.

       3.1.4.5    Zero Liquid Discharge

       Zero liquid discharge (ZLD) systems are systems that do not generate a waste stream that
is discharged from the plant.  Based on information EPA has collected during the 2007/2008
detailed study, five main types of ZLD systems are available to treat FGD wastewater:
evaporation with distillate recovery, complete recycle, evaporation ponds, conditioning dry fly
ash, and underground injection.  The subsections below discuss the wastewater treatment
processes for each of these ZLD systems.

       There is one coal-fired power plant in the U.S. that is currently installing an evaporator to
treat FGD scrubber purge resulting  in a zero liquid discharge [Water Online, 2007b].  In
addition, there are six coal-fired power plants in Italy that are operating or in the process of
installing evaporators to treat FGD  scrubber purge [Industrial Water World, 2006; Water Online,
2007a]. EPA has identified 27 coal-fired plants that are operating their FGD systems with
complete recycle of the scrubber purge.  Additionally, EPA has identified two plants that prevent
discharging FGD wastewater by using evaporation ponds, and another plant that uses the FGD
wastewater to condition the dry fly  ash generated.  Underground injection is currently being used
to dispose of FGD wastewater at one coal-fired power plant, with another plant  slated to  do so
starting next year.

       Evaporation with Distillate Recovery

       Evaporators in combination with a final drying process can eliminate the discharge of
certain wastewater streams at various types of industrial plants, including power plants, oil
refineries, and chemical plants. The evaporation ZLD system uses a falling-film evaporator (also
referred to as a brine  concentrator) to produce a concentrated wastewater stream and a reusable
distillate stream.  The concentrated  wastewater stream may be further processed in a crystallizer
or spray dryer, in which the remaining water is evaporated, eliminating the wastewater stream.
When used in conjunction with a crystallizer or spray dryer, this process eliminates the liquid
discharge stream by generating clean distillate and a solid by-product that can then be disposed
of in a landfill.

       At power plants, evaporators are most often used to treat waste streams such as cooling
tower blowdown and demineralizer waste, but coal-fired power plants have recently begun to
consider, install,  and  operate evaporator systems for the treatment of FGD wastewater as well.
In Italy, two coal-fired power plants have recently begun treating FGD wastewater with
evaporator systems, and several other plants are installing evaporator systems for the  treatment

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
of FGD wastewater.  In the United States, there are currently no evaporator systems treating
FGD wastewater, but there is at least one plant installing an evaporator system for the treatment
of FGD wastewater.

       In an evaporator system used to treat FGD wastewater, the first step is to adjust the pH of
the FGD scrubber purge to approximately 6.5. After the pH adjustment, the scrubber purge is
sent through a heat exchanger to bring the waste stream to its boiling point. The waste stream
continues to a deaerator where the noncondensable materials such as carbon dioxide and oxygen
are vented to the atmosphere. [Aquatech, 2006]

       From the deaerator, the waste stream enters the sump of the brine concentrator. Brine
from the sump is pumped to the top of the brine concentrator and enters the heat transfer tubes.
While falling down the heat transfer tubes, part of the solution is vaporized and then compressed
and introduced to the shell side of the brine concentrator. The temperature difference between
the vapor and the brine solution causes the vapor to transfer heat to the brine solution, thereby
condensing the compressed vapor as distilled water and vaporizing some of the brine solution.
The condensed vapor (distillate water) is recycled within the plant, typically as boiler make-up
water. [Aquatech, 2006]

       To prevent scaling within the brine concentrator as a result of the gypsum present in the
FGD scrubber purge, the brine concentrator is seeded with calcium sulfate. The calcium salts
preferentially precipitate onto the seed crystals instead of the tube surfaces of the brine
concentrator. [Shaw, 2008]

       The concentrated brine slurry from the brine concentrator tubes falls into the sump and is
recycled with the feed back to the top of the brine concentrator for additional processing, while a
small amount is continuously withdrawn from the sump and transferred for additional
processing. The brine concentrator can typically concentrate the FGD scrubber purge five to ten
times, which reduces the inlet FGD scrubber purge water volume by 80 or 90 percent. [Shaw,
2008]

       Three options are typically considered to be available for eliminating the brine
concentrate: (1) final evaporation in a brine crystallizer; (2) evaporation in a spray dryer; or (3)
using the brine to condition dry fly ash or other solids and disposal of the mixture in a landfill.

       There are a large number of plants currently using brine concentrators to treat a waste
stream other than FGD scrubber purge (e.g., cooling tower blowdown). For these non-FGD
systems, the concentrated brine withdrawn from the sump would typically be sent to a forced-
circulation crystallizer to evaporate the remaining water from the concentrate and generate a
solid product for disposal.  However, the calcium and magnesium salts present in the scrubber
purge can pose difficulties for the forced-circulation crystallizer. To prevent this, the FGD
scrubber purge can be pretreated using a lime-softening process (i.e., chemical precipitation)
upstream of the brine concentrator. With water softening, the magnesium and calcium ions
precipitate out of the purge water and are replaced  with sodium ions, producing an aqueous
solution of sodium chloride that can be more effectively treated with a forced-circulation
crystallizer. [Shaw, 2008]
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       Coal-fired power plants can avoid having to operate the chemical precipitation
pretreatment process by using a spray dryer to evaporate the residual waste stream from the brine
concentrator.  This approach will create a solid product that can be landfilled. Another
alternative to the brine crystallization process is to blend the concentrated brine waste stream
with dry fly ash or other solids, and dispose of the resulting mixture in a landfill.

       Complete Recycle

       As discussed in Section 3.1.1, plants that are not producing a reusable solid product from
the FGD system (e.g., wallboard-grade gypsum), may be capable of operating the system without
producing a scrubber purge waste stream.  Because the solids are being landfilled, the plant will
not have a chloride specification for the solids; therefore, the plant will not need to rinse the
solids to remove the chlorides before the solids are dewatered.  If the plant is able to balance the
chlorides generated in the FGD scrubber system with the chlorides retained in the solids that are
sent to the landfill, then the plant may be able to operate without a scrubber purge [Sargent &
Lundy, 2007].

       The other parameter that must be controlled to achieve complete recycle of the FGD
wastewater is a negative water balance for the system.  Without a negative water balance,  some
of the FGD wastewater would have to be discharged, or recycled elsewhere within the plant, to
prevent the build up of water in the system. Most of the water entering the FGD  system is from
the sorbent (e.g., lime or limestone) preparation which feeds the sorbent slurry to the FGD
scrubber. Additional water is used for washing the mist eliminators, water seal for the vacuum
filter seal pumps, and other various equipment washings [Babcock & Wilcox, 2005]. Most of
the water entering the system is evaporated as the flue gas is quenched in the FGD scrubber. In
addition, water exits the system in the solids disposal, and if necessary, in  a scrubber purge
stream [Babcock &Wilcox, 2005].  Therefore, if enough chlorides  are retained in the calcium
sulfite or gypsum solids that are sent to the landfill, then the plant can operate without a scrubber
purge.

       Evaporation Ponds

       Some power plants located in the southwestern United States use evaporation ponds to
achieve zero liquid discharge. Because of the warm, dry climate in this region, the plants  can
send the FGD wastewater to one or more ponds where the water is allowed to evaporate. At
these plants, the evaporation rate achieved by the pond is greater than or equal to the flow rate of
the FGD wastewater to the pond and no water is discharged from the evaporation pond.

       Conditioning Dry Fly Ash

       Many plants that operate dry fly ash handling systems need to condition the dry fly ash
with water to prevent the fly ash from blowing away while it is being trucked to the landfill or
other disposal. EPA has identified one plant that uses FGD wastewater to  condition its dry fly
ash.  In addition, there is another plant that will use an evaporation system in combination with
conditioning dry fly ash to achieve zero liquid discharge [Water Online, 2007b].  The plant will
use the evaporation system to reduce the volume of the FGD scrubber purge waste stream, and
the effluent from the brine concentrator will be mixed with dry fly ash and disposed of in a
landfill.

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       Underground Injection

       Underground injection is a technique used to dispose of wastes by injecting them into an
underground well. This technique is an alternative to discharging wastewater to surface waters.
High pressure pumps are used to inject the wastewater into the concrete-lined wells.  The bottom
of the well is located between impermeable rock surfaces, which prevent the waste from
reaching potable water aquifers.  One plant is currently using underground injection for the
disposal of FGD scrubber purge and a second plant is expected to begin injecting its scrubber
purge for disposal in 2009.  Underground injection has  its own permitting and regulations, which
are not covered under the NPDES program.

       3.1.4.6    Other Technologies under Investigation

       EPRI is currently conducting studies to evaluate and demonstrate technologies that have
the potential to remove trace metals, specifically mercury and selenium, from FGD wastewater.
Some of the technologies being studied are already being used to treat FGD wastewater. EPRI is
conducting pilot- and full-scale optimization field studies of these developed technologies,
including chemical precipitation (organosulfide and iron coprecipitation), constructed wetlands,
and an anoxic/anaerobic biological treatment system. Other technologies being studied have
been demonstrated on other industrial wastewaters, but have not been tested on FGD
wastewaters. [EPRI, 2008a]

       Iron Cementation

       EPRI has conducted laboratory feasibility studies of the metallic iron cementation
treatment technology as a method for removing all species of selenium from FGD wastewater.
The iron cementation process consists of contacting the FGD wastewater with an iron powder,
which reduces the selenium to its elemental form (cementation). The pH of the wastewater is
raised to form hydroxides and the slurry is filtered to remove the precipitates from the
wastewater. The iron powder used in the process is separated from the wastewater and recycled
back to the cementation step. From the initial studies, EPRI concluded that the metallic iron
cementation approach is promising for treating FGD wastewater for multiple species of
selenium, including  selenite, selenate, and other unknown selenium compounds.  EPRI is
planning to continue conducting laboratory- and pilot-scale feasibility studies of the technology
to evaluate selenium and mercury removal performance. [EPRI, 2008b]

       Reverse Osmosis

       Reverse osmosis systems are currently in use at power plants, usually for the treatment of
cooling tower blowdown wastewaters to achieve a zero liquid discharge. EPRI has identified a
high efficiency reverse osmosis (HERO™) process that allows the reverse osmosis system to
operate at a high pH, which allows the system to treat high silica wastewaters because silica is
more  soluble at higher pHs. The wastewater undergoes a water softening process to raise the pH
of the wastewater before the HERO™ system.

       Although the HERO™ system has been demonstrated for use with power plant cooling
tower blowdown wastewater, the system has potentially limited use for FGD wastewater due to

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
the osmotic pressure of the FGD wastewater resulting from the high chloride and TDS
concentrations.  If the osmotic pressure of the FGD wastewater exceeds the pressure capacity of
the membrane, then the reverse osmosis system cannot be used. [EPRI, 2007a]

       The use of the HERO™ system for the treatment of FGD wastewater may not be possible
at many power plants; however, some plants with lower TDS and chloride concentrations may be
able to operate these systems.  The HERO™ system is of particular interest for the treatment of
boron from FGD wastewaters because boron becomes ionized at an elevated pH and therefore,
could be removed using a reverse osmosis system. [EPRI, 2007a]

       Sorption Media

       Sorption media has been used by the drinking water industry to remove arsenic from the
drinking water.  These sorption processes are designed to adsorb pollutants onto the media's
surface area using physical and chemical reactions. The designs most commonly used in the
drinking water industry use metal-based adsorbents, typically granular ferric oxide, granular
ferric hydroxide, or titanium based oxides.  The sorption media is usually a single use application
which can typically be disposed of in a non-hazardous landfill after its use. In addition, the
single use design prevents the plant from needing any further treatment of the residuals.
According to EPRI, these sorption media have shown removals for the common forms of arsenic
and selenium from drinking water. [EPRI, 2007a]

       Ion Exchange

       Ion exchange systems are currently in use at power plants for the pretreatment of boiler
make up water.  Ion exchange systems are designed to remove specific constituents from
wastewater; therefore, specific metals can be targeted by the system.  The ion exchange process
does not generate any residual sludge; however, is does generate a regenerant stream which
contains the metals stripped from the wastewater.  EPA has compiled information on a plant that
is pilot testing two ion exchange resins this  year.  [EPRI, 2007a]

       Electro-Coagulation

       Electro-coagulation is a technology that uses an electrode to introduce an electric charge
to the wastewater, which neutralizes the electrically charged colloidal particles.  These systems
typically use aluminum or iron electrodes, which are dissolved into the waste stream during the
process. The dissolved metallic ions precipitate with the other pollutants present in the
wastewater and form insoluble metal hydroxides.  According to EPRI, additional polymer or
supplemental coagulants may need to be added to the wastewater depending on the specific
characteristics.  These systems are typically used to treat small waste streams, ranging from 10 to
25 gpm; however, systems up to 50 or 100 gpm may be reasonable.  [EPRI,  2007a]

       Other Technologies

       Other technologies under laboratory-scale study include polymeric chelates, taconite
tailings, and nano-scale iron reagents. In addition, EPRI is investigating various physical
treatment technologies, primarily for mercury removal, including filtration. [EPRI, 2008a]
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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
3.2    Ash Handling Operations

       Combusting coal in steam electric boilers generates solid, noncombustible constituents of
the coal, referred to as ash.  The heavier ash particles collect on the bottom of the boiler and are
referred to as bottom ash. The finer ash particles are light enough to be transferred out of the
boiler with the flue gas exhaust and are referred to as fly ash. The characteristics of the ash
depend on the type of fuel combusted, how it is prepared prior to combustion, and the operating
conditions of the boiler. This section discusses the operations for handling these ash particles
and the wastewater generated from the ash handling operations.

3.2.1   Process Description and Wastewater Generation

       This section describes the steam electric generating processes for fly ash and bottom ash
based on data collected by EPA throughout the 2007/2008 detailed study.

       3.2.1.1    Fly Ash Handling Operations

       To remove the fly ash particles from the flue gas at coal-fired power plants, most plants
operate electrostatic precipitators (ESPs). The ESPs use high voltage to generate an electric
charge on the particles contained in the flue  gas. The charged particles then collect on a metal
plate with an opposite electric charge.  As the particles begin to layer on the metal plates, the
plates are tapped/rapped to loosen the particles, which fall into collection hoppers.  Each unit has
multiple hoppers that collect ash  from different locations within the ESP.  The hoppers located
closer to the inlet of the ESP collect the larger fly ash particles that are removed more easily, and
the hoppers located closer to the outlet of the ESP  collect the finer fly ash particles that are more
difficult to remove.  In addition, the hoppers at the inlet collect more fly ash than the hoppers at
the outlet of the ESP.

       Once the fly ash is collected in the hoppers, the plant can either handle the fly ash in a dry
or wet fashion.  Plants that operate a dry fly  ash handling system pneumatically transfer the fly
ash from the hoppers to fly ash storage silos. From the silos, the fly ash is loaded into trucks and
either hauled to a landfill for disposal or hauled off site for beneficial reuse, such as cement
manufacturing.

       Plants that operate a wet fly ash handling system use a wastewater stream (e.g., service
water) to sluice the fly ash out of the hoppers. The water stream used to sluice the fly ash from
the hoppers does not flow through the hoppers, but instead flows through piping connected to the
hoppers. The flowing stream creates a vacuum that pulls the fly ash out of the hoppers. Plants
usually have a sluice stream for each individual ESP, which operates  continuously.  Because
each ESP has more than one hopper, the plant is continuously cycling through each of the
hoppers based on which hopper contains the most fly ash at a given time.  The inlet hoppers are
sluiced more frequently or for longer periods because they collect more fly ash than the outlet
hoppers. This fly ash sluice is most commonly sent to a wet impoundment, referred to as an ash
pond.
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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       3.2.1.2    Bottom Ash Handling Operations

       Most coal-fired boilers currently in operation in the United States operate dry-bottom
boilers as opposed to wet-bottom boilers [Babcock &Wilcox, 2005]. The primary difference
between these two types of boilers is that bottom ash is intentionally maintained in a molten,
fluid state in the lower portion of a wet-bottom boiler, whereas the bottom ash in a dry-bottom
boiler is solidified in the lower portion of the boiler [Babcock &Wilcox, 2005].  The remainder
of this discussion focuses on the bottom ash handling operations for a dry-bottom boiler.

       In a typical dry-bottom boiler, the lower portion of the boiler slopes inward from the front
and rear walls of the boiler, leaving a three- to four-foot opening that runs the width of the
bottom of the boiler. These sloped walls and opening allow the bottom ash to feed by gravity to
the bottom ash hoppers that are positioned below the boiler. The bottom ash hoppers are
connected directly to the boiler bottom to prevent any boiler gases from leaving the boiler. The
hoppers have sloped side walls as well, except the hoppers' left and right walls slope  downward,
which allows the hoppers to have a single exit point.  Depending on the size of the boiler, there
may be more than one bottom ash hopper running along the opening of the bottom of the boiler.
The bottom ash hoppers are filled with water to quench the hot bottom ash as it enters the
hopper. [Babcock & Wilcox, 2005]

       Once the bottom ash hoppers have filled with bottom ash, a gate at the bottom of the
hopper opens and the ash is directed to grinders to grind the bottom ash into smaller pieces
[Babcock & Wilcox, 2005]. After the bottom ash hoppers below the boiler have been emptied,
the gate at the bottom of the hoppers close and the hoppers again fill with water.  The bottom ash
hoppers are typically sized to accommodate  approximately 8 hours worth of bottom ash
generation [Babcock & Wilcox, 2005]; therefore, the bottom ash is sluiced about two to four
times a day. The frequency of bottom ash sluicing depends upon the hopper size and the
operation of the boiler. The duration of the bottom ash sluice depends upon the number and size
of hoppers and the bottom ash sluice flow rate.  From EPA's site visit experiences, the bottom
ash sluice duration was generally between 30 minutes to one hour for  each unit.

       After the bottom ash has been ground, the ash is sluiced with water and pumped either to
a pond or a dewatering hydrobin10.  Because the bottom ash particles are heavier than the fly ash
particles, they are more easily separated from the sluice water than the fly ash particles. In
addition, if the bottom ash sluice water is treated in an ash pond or in a hydrobin system, then the
overflow from these systems can be recycled elsewhere within the plant. During the  site visit
program, EPA visited two plants with segregated bottom ash handling systems and these plants
reused the bottom ash overflow to sluice more bottom ash. These plants only discharged the
bottom ash overflow if the water began accumulating in the system and needed to be  discharged
for volume  control.

3.2.2  Ash Sluice Water Characteristics

       This section  discusses the wastewater characteristics of fly ash and bottom ash
wastewaters based on information EPA has collected thus far in the study. Section 3.2.1
discusses how these wastewaters  are generated, while this section discusses what constituents
10 Some plants operate dry bottom ash handling systems. Ash handled in a dry fashion is typically transferred to
landfills.	
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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
may be present in the wastewater as well as the flow rates reported.  In addition, this section
presents concentration data (as available) for pollutants present in the waste stream samples that
were collected during the EPA wastewater sampling program, as well  as flow rate data from
responses to EPA's data request. See Chapter 2 for background regarding EPA's data collection
activities.

       As described in Section 3.2.1.1, the fly ash sluice waste stream is usually a continuous
stream from each of the coal-fired units. Fly ash sluice is one of the larger volume flows for
coal-fired power plants. Table 3-9 presents the fly ash sluice flow rates reported in the data
request responses. The flow rates that are normalized on a MW basis  are based on the plants'
total coal-fired capacity. The average coal-fired capacity per plant is 1,210 MW and the median
coal-fired capacity per plant is 1,140 MW.

       Sluice flow rates are not the same as pond overflow rates.  In addition to the  sluice flow,
ash ponds typically receive other waste streams.  Factors acting to reduce the pond overflow rate
include pond losses from infiltration and evaporation, and whether the water held in the ash pond
is recycled back to the plant for reuse. The average fly ash pond overflow flow rates collected
during the development of the 1982 effluent guidelines are 2,610,000 GPD/plant and 3,810
GPD/MW.  [U.S. EPA, 1982].

                           Table 3-9. Fly Ash Sluice Flow Rates

Number of
Plants
Average Flow Rate a
Median Flow Rate a
Range of Flow Rate a
Flow Rate per Plant
GPM/plantb
GPD/plant d
GPY/plantd
17
17
17
5,890
7,640,000
2,710,000,000
3,000
4,030,000
1,470,000,000
188 - 27,500
270,000 - 39,600,000
6,480,000 -
14,500,000,000
Normalized Flow Rate based on Total Coal-Fired Capacity
GPM/Coal-Fired MW b' c
GPD/Coal-FiredMWc'd
GPY/Coal-Fired MW c' d
17
17
17
4.59
5,830
2,090,000
4.08
5,140
1,870,000
0.291-9.38
419-11,900
2,050 - 4,350,000
Source: [U.S. EPA, 2008a]
a - The flow rates presented have been rounded to three significant figures.
b - The GPM flow rate represents the flow rate during the actual sluice.
c - For this analysis, EPA assumed that the total capacity for each coal-fired steam electric unit is associated with
coal use.  Non-coal-fired units are not included in the capacity calculations.
d - Because the fly ash sluice flow rate is not always continuous, the GPD cannot be directly calculated from the
GPM. Similarly, some of the fly ash sluice flows are not generated 365 days per year, so GPY cannot be directly
calculated from GPD.

       As  described in Section 3.2.1.2, bottom ash sluice is an intermittent stream from each of
the coal-fired units.  The bottom ash sluice flow rates are typically not as large as the fly ash
sluice flow rates, as typically more fly ash than bottom  ash is generated in coal-fired boilers, but
bottom ash sluice is still one of the larger volume flows for steam electric plants.
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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       Table 3-10 presents the bottom ash sluice flow rates reported in the data request
responses. The flow rates that are normalized on a MW basis are based on the plants' total coal-
fired capacity.  The average coal-fired capacity per plant is 1,570 MW and the median coal-fired
capacity per plant is 1,560 MW.

       As was noted above, sluice flow rates are not the same as pond overflow rates. The
average bottom ash pond overflow flow rates collected during the development of the 1982
effluent guidelines are 2,600,000 GPD/plant and 3,880 GPD/MW. [U.S. EPA, 1982].

       Table 3-10. Bottom Ash Sluice Flow Rates from EPA Data Request Responses

Number of
Plants a
Average Flow
Rateb
Median Flow
Rateb
Range of Flow
Rateb
Flow Rate per Plant
GPM/plant c
GPD/plant e
GPY/plant e
27
27
27
3,370
3,290,000
1,190,000,000
1,740
2,380,000
810,000,000
358 - 12,600
253,000 -
18,100,000
92,400,000 -
6,600,000,000
Normalized Flow Rate Based on Total Coal-Fired Capacity
GPM/Coal-FiredMWc'd
GPD/Coal-Fired MW 4 e
GPY/Coal-FiredMW46
27
27
27
2.21
1,940
701,000
1.18
1,600
585,000
0.479-9.38
222 - 7,070
81,100-2,580,000
Source: [U.S. EPA, 2008a]
a - 29 of the 30 data request plants reported generating bottom ash sluice; however, two plants are excluded from
this summary because they were unable to reasonably estimate the bottom ash sluice flow rates.
b - The flow rates presented have been rounded to three significant figures.
c - The GPM flow rate represents the flow rate during the actual sluice.
d - For this summary, EPA assumed that the total capacity for each coal-fired steam electric unit is associated with
coal use. Non-coal-fired units are not included in the capacity calculations.
e - Because the bottom ash sluice flow rate is not always continuous, the GPD cannot be directly calculated using
only the GPM. Similarly, some of the bottom ash sluice flows are not generated 365 days per year, so GPY cannot
be directly calculated from GPD.

       The pollutant concentrations in ash sluice wastewater vary from plant to plant depending
on the coal used, the type of boiler, and the particulate control system used by the  plant.  In
addition, the waste stream characteristics also vary in a cyclical fashion during the discharges.
For example, the fly ash sluice characteristics vary depending on which of the ash hoppers is
being sluiced and the bottom ash sluice characteristics at the beginning of the intermittent
sluicing period are likely to be different than the characteristics at the end of the sluice period.
Table 3-11 presents the pollutant concentrations representing the influent to the ash pond
systems.
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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                       Table 3-11. Ash Pond Influent Concentrations
Analyte
Method
Unit
Widows Creek - Diked
Channel Influent to
Combined Ash Pond a'b
Cardinal - Influent to
Fly Ash Pond a
Routine Metals - Total
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
Zinc
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
94,800
ND (38.0)
131
6,080
11.3
4,330
ND (9.50)
103,000
107
ND (95.0)
188
80,700
208
25,700
337
2.66
65.5
ND (95.0)
27.5
31,200
ND (19.0)
7,150
346
133
785
320,000
ND (81.2)
1,520
5,060
71.5
2,790
39.6
204,000
1,300
381
964
298,000
786
35,100
1,120
2.31
333
739
ND (20.3)
69,900
ND (40.6)
24,900
2,340
521
1,220
Routine Metals - Dissolved
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Hexavalent Chromium
Cobalt
Copper
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
D 1687-92
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
663
ND (20.0)
46.0
178
ND (5.00)
2,150
ND (5.00)
40,300
ND (10.0)
ND (2.00)
ND (50.0)
ND (10.0)
283
ND (20.0)
86.8
164
ND (5.00)
1,380
ND (5.00)
94,800
ND (10.0)
5.00
ND (50.0)
ND (10.0)
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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                       Table 3-11. Ash Pond Influent Concentrations
Analyte
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
Zinc
Method
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
Unit
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
Widows Creek - Diked
Channel Influent to
Combined Ash Pond a'b
ND (100)
ND (50.0)
7,110
ND (15.0)
ND (0.200)
50.1
ND (50.0)
26.8
13,400
ND (10.0)
ND (10.0)
66.8
ND (5.00)
ND (10.0)
Cardinal - Influent to
Fly Ash Pond a
ND (100)
ND (50.0)
15,200
40.3
ND (0.200)
243
ND (50.0)
16.6
64,400
ND (10.0)
ND (10.0)
70.7
ND (5.00)
ND (10.0)
Low-Level Metals - Total
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
13.1 L
88.9
ND (20.0)
ND (160)
114
104
1.02
ND (200)
ND (200)
ND (4.00)
198
33.1
519
9.51
569
719
260
1.16
291
ND (200)
43.6
720
Low-Level Metals - Dissolved
Antimony
Arsenic
Cadmium
Chromium
Hexavalent Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1636
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
8.54
49.5
ND (2.00)
ND (16.0)
NA
ND (4.00)
ND (1.00)
ND (0.000500)
ND (20.0)
ND (100)
ND (0.400)
ND (10.0)
17.4
80.7
ND (1.00)
ND (80.0)
NA
ND (20.0)
ND (0.500)
0.000550
ND (100)
21.2
3.10
ND (50.0)
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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                       Table 3-11. Ash Pond Influent Concentrations
Analyte
Method
Unit
Widows Creek - Diked
Channel Influent to
Combined Ash Pond a'b
Cardinal - Influent to
Fly Ash Pond a
Classical*
Ammonia As Nitrogen (NH3-
N)
Nitrate/Nitrite (NO3-N + NO2-
N)
Total Kjeldahl Nitrogen (TKN)
Biochemical Oxygen Demand
(BOD)
Chloride
Hexane Extractable Material
(HEM)
Silica Gel Treated HEM (SGT-
HEM)
Sulfate
Total Dissolved Solids (TDS)
Total Phosphorus
Total Suspended Solids (TSS)
4500-
NH3F
353.2
4500-N,C
5210B
4500-CL-C
1664A
1664A
D5 16-90
2540 C
365.3
2540 D
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
0.400
0.360
7.41
53.0
21.4
ND (5.00)
NA
58.1
224
16.6
9,190 E
0.170
2.65
1.01
ND (2.00)
56.8
7.00
6.00
1,110
662
4.03
23,400
Source: [ERG, 20081], [ERG, 2008n]
a - The concentrations presented have been rounded to three significant figures.
b - The sample collected from the diked channel influent to the combined ash pond represents only the wastewaters
associated with six of the eight generating units. The wastewaters for the other two units enter the combined ash
pond at a different point.
E - Sample analyzed outside holding time.
L - Sample result between 5x and lOx blank result.
NA - Not analyzed.
ND - Not detected (number in parenthesis is the report limit). The sampling episode reports for each of the
individual plants contains additional sampling information, including analytical results for analytes measured above
the detection limit, but below the reporting limit (i.e., J-values).

       For the Widows Creek sampling episode, EPA collected a 12-hour composite sample of
the influent to the ash pond from a diked channel containing fly ash sluice, bottom ash sluice,
and several low-volume wastewaters, including coal pile runoff overflow, boiler blowdown,
nonchemical metal cleaning wastewater, roof and switchyard drainage, flow wash water, and
miscellaneous cooling water.  EPA collected the samples from the diked channel  at a point
downstream of the influent to the channel to allow for some initial solids settling, but upstream
of the open water area of the ash pond.  The wastewater contained within the diked channel
represents the wastewater generated from six of the eight units at the plant, which represents
approximately 42 percent of the plant's generating capacity. The other two units  also generate
wastewaters that enter the ash pond; however, the wastewaters enter the pond at a different
location.  Plant personnel estimated that the flow rate  entering the ash pond at the time of
sampling for the six units was approximately 12.1 mgd. The sampling episode report for
Widows Creek contains more detailed information regarding the sample collection procedures
[ERG, 2008n].
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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       For the Cardinal sampling episode, EPA collected a three-hour composite sample of the
influent to the fly ash pond.  The influent to the fly ash pond consisted of fly ash sluice water and
some dilution water (approximately one-third of the total influent flow). The fly ash is collected
by ESPs at the plant and sluiced to the fly ash pond. During the sampling episode, the plant
personnel estimated the influent flow rate to the fly ash pond was 6,330 gpm. The sampling
episode report for Cardinal contains more detailed information regarding the sample collection
procedures [ERG, 20081].

       Table 3-11 shows that the ash sluice waste streams contain significant concentrations of
TSS and metals.  The ash sluice metals concentrations are typically lower than those of the FGD
wastewater (see Table 3-6), but the TSS concentration is higher. Many of the metals in the ash
sluice stream are primarily present in the particulate phase. The TSS and metals concentrations
present in the ash sluice water are large enough that the waste  stream typically requires some
form of treatment prior to being discharged, at a minimum to lower the TSS concentrations to
meet the 30 mg/L (30-day average) ELG limit for fly ash and bottom ash transport water (see
Section 3.2.3 for more details).

       Table 3-12 presents the pollutant concentrations representing the effluent from ash ponds.
Each of these pond systems treats different types of wastewater; therefore, the various effluents
cannot be directly compared with each other. In addition, the influent concentrations presented
in Table 3-11 for Widows Creek should not be directly compared with the effluent
concentrations in Table 3-12 because the influent  only represents a portion of the waste streams
entering the pond system.

       Homer City operates a dry fly ash handling system and a wet bottom ash handling
system. The bottom ash sluice water from Homer City is first transferred to hydrobins, which
remove approximately 90 to 95 percent of the solids from the wastewater. The overflow from
the hydrobins is transferred to the two bottom ash ponds operating in parallel. The overflow
from the bottom ash ponds is transferred to a clearwell and then discharged or reused to sluice
more bottom ash. EPA collected a grab sample of the effluent from the bottom ash treatment
system at Plant E directly from the clearwell. The average flow rate discharged from the
clearwell during the sampling episode was 314.5 gpm.  The sampling episode report for Homer
City contains more detailed information regarding the sample  collection procedures [ERG,
2008J].

       Widows Creek operates a combined fly ash and bottom ash pond system.  The fly ash
from seven of the eight units (one unit uses the FGD system for particulate control) and bottom
ash from all eight units, as well as several other low-volume wastewaters enter the combined ash
pond. The wastewater entering the ponds is first collected in two different sumps; from each
sump the wastewater flows by gravity through diked channels made of ash until it reaches the
main pond. The overflow from the main ash pond flows to a second pond where the plant injects
carbon dioxide, if needed, to decrease the pH of the wastewater to within the range of 6.0 to 9.0.
The overflow from the second pond enters the pumping basin, where the treated wastewater is
pumped to a canal where the plant draws intake water from the river. Alternatively,  if the
pumping basin begins to overflow, then the plant has an emergency overflow discharge directly
to surface water.  EPA collected a grab sample of the effluent from the combined ash pond
directly from the pumping basin. EPA estimated that the average flow rate discharged from the
pumping basin during the sampling episode was 29.9 mgd. The sampling episode report for
                                         3^53

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
Widows Creek contains more detailed information regarding the sample collection procedures
[ERG, 2008n].

       Mitchell operates a fly ash pond treatment system. The fly ash pond receives the fly ash
sluice water from Mitchell, fly ash sluice from a neighboring power plant, wastewater from a
coal washing preparation plant, treated acid mine drainage wastewater, and stormwater runoff.
The waste streams enter the fly ash pond at various locations within the pond and flow to the
dam located at the end of the pond. The dam controls the flow from the pond into a channel that
discharges to surface water. EPA collected a grab sample of the effluent from the fly ash pond
from the channel discharging to the surface water. The average flow rate discharged from the fly
ash pond during the sampling episode was 5,400 gpm.  The sampling episode report for Mitchell
contains more detailed information regarding the sample collection procedures [ERG, 2008k].

       Cardinal operates a fly ash pond treatment system. The fly ash pond receives fly ash
sluice water and occasionally some dilution water.  The ash sluice water and dilution water enter
at the same point in the pond and flow to the dam located at the opposite end of the pond.  The
dam controls the flow from the pond into a channel that discharges to surface water.  EPA
collected a grab sample of the effluent from the fly ash pond from the channel discharging to the
surface water. The average flow rate discharged from the fly ash pond during the sampling
episode was 5,416 gpm.  The sampling episode report for Cardinal contains more detailed
information regarding the sample collection procedures [ERG, 20081].

       Table 3-12 shows that the treated ash pond effluent wastewaters contain low
concentrations of TSS and most nutrients; however, metals are still present in the wastewater.
Table 3-12  also shows that most of the metals present in the treated ash pond wastewater are
predominantly in the dissolved phase.
                                          3-54

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                                         Table 3-12. Ash Pond Effluent Concentrations
Analyte
Method
Unit
Homer City -
Effluent from Bottom
Ash Pond a
Widows Creek-
Effluent from
Combined Ash Pond a
Mitchell - Effluent
from Fly Ash Pond a
Cardinal - Effluent
from Fly Ash Pond a'b
Routine Metals - Total
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
Zinc
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
323
ND (20.0)
ND (10.0)
101
ND (5.00)
396
ND (5.00)
186,000
ND (10.0)
ND (50.0)
ND (10.0)
355
ND (50.0)
31,800
128
ND (0.200)
19.7
ND (50.0)
6.02
106,000
ND (10.0)
ND (10.0)
ND (20.0)
ND (5.00)
21.6
1,070
ND (20.0)
38.2
227
ND (5.00)
2,210
ND (5.00)
58,500
13.5
ND (50.0)
ND (10.0)
144
ND (50.0)
6,680
ND (15.0)
ND (0.200)
143
ND (50.0)
16.2
21,300
ND (10.0)
14.5
68.5
ND (5.00)
ND (10.0)
404
24.6
150
133
ND (5.00)
2,350
ND (5.00)
115,000
15.9
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
21,000
ND (15.0)
ND (0.200)
359
ND (50.0)
177
526,000
ND (10.0)
ND (10.0)
110
ND (5.00)
ND (10.0)
344
21.2
77.6
165
ND (5.00)
1,100
ND (5.00)
88,400
ND (10.0)
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
17,900
64.7
ND (0.200)
361
ND (50.0)
44.5
70,800
ND (10.0)
12.6
104
ND (5.00)
ND (10.0)

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                                         Table 3-12. Ash Pond Effluent Concentrations
Analyte
Method
Unit
Homer City -
Effluent from Bottom
Ash Pond a
Widows Creek-
Effluent from
Combined Ash Pond a
Mitchell - Effluent
from Fly Ash Pond a
Cardinal - Effluent
from Fly Ash Pond a'b
Routine Metals - Dissolved
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Hexavalent Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Thallium
Titanium
Vanadium
Yttrium
Zinc
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
D 1687-92
200.7
200.7
200.7
200.7
200.7
200.7
245.1
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
200.7
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
231
ND (20.0)
ND (10.0)
106
ND (5.00)
397
ND (5.00)
192,000
ND (10.0)
ND (2.00)
ND (50.0)
ND (10.0)
106
ND (50.0)
32,600
129
ND (0.200)
20.2
ND (50.0)
6.10 L
106,000
ND (10.0)
ND (10.0)
ND (20.0)
ND (5.00)
35.2
357
ND (20.0)
30.1
206
ND (5.00)
2,200
ND (5.00)
55,400
11.9
12.0
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
6,430
ND (15.0)
ND (0.200)
136
ND (50.0)
15.3
20,000
ND (10.0)
ND (10.0)
64.7
ND (5.00)
ND (10.0)
241
23.9
138
128
ND (5.00)
2,290
ND (5.00)
113,000
14.1
7.00
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
20,300
ND (15.0)
ND (0.200)
330
ND (50.0)
162
514,000
ND (10.0)
ND (10.0)
108
ND (5.00)
ND (10.0)
130 L
20.9
74.6
157
ND (5.00)
1,090
ND (5.00)
87,200
ND (10.0)
<3.50
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
17,700
42.9
ND (0.200)
352
ND (50.0)
43.8
70,300
ND (10.0)
ND (10.0)
99.9
ND (5.00)
ND (10.0)

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                                         Table 3-12. Ash Pond Effluent Concentrations
Analyte
Method
Unit
Homer City -
Effluent from Bottom
Ash Pond a
Widows Creek-
Effluent from
Combined Ash Pond a
Mitchell - Effluent
from Fly Ash Pond a
Cardinal - Effluent
from Fly Ash Pond a'b
Low-Level Metals - Total
Antimony
Arsenic
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
1.09
6.52
ND (0.500)
ND (4.00)
2.37
ND (0.250)
0.00511
10.7
5.74
1.32
24.2
4.39
34.9
ND (0.500)
13.5 L
1.49
0.490
0.00157
ND (5.00)
17.1
1.46
ND (2.50)
25.8
142
1.32
20.4
5.47
0.580
0.00212
11.0
191
1.72
10.1
21.9
69.8
1.14
4.64 L
2.98
0.420
0.00125
10.7
45.8
2.84
5.98
Low-Level Metals - Dissolved
Antimony
Arsenic
Cadmium
Chromium
Hexavalent Chromium
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
1638
1638
1638
1638
1636
1638
1638
163 IE
1638
1638
1638
1638
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
UG/L
0.990
5.00
ND (0.500)
ND (4.00)
3.01
2.08
ND (0.250)
0.00141
10.4
5.16
1.31
15.0
4.45
29.0
ND (0.500)
12.6 L
14.7
ND (1.00)
ND (0.250)
ND (0.000500)
ND (5.00)
15.6
1.49
ND (2.50)
22.5
131
1.17
16.0
17.4
4.54
ND (0.250)
ND (0.000500)
9.57
161
1.42
9.51
22.4
68.9
1.11
4.49 L
3.96
2.27
ND (0.250)
ND (0.000500)
10.6
45.0
2.87
4.15

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       2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
                                                    Table 3-12.  Ash Pond Effluent Concentrations
Analyte
Method
Unit
Homer City -
Effluent from Bottom
Ash Pond a
Widows Creek-
Effluent from
Combined Ash Pond a
Mitchell - Effluent
from Fly Ash Pond a
Cardinal - Effluent
from Fly Ash Pond a'b
Classical*
Ammonia As Nitrogen (NH3-N)
Nitrate/Nitrite (NO3-N + NO2-N)
Total Kjeldahl Nitrogen (TKN)
Biochemical Oxygen Demand
(BOD)
Chloride
Hexane Extractable Material
(HEM)
Silica Gel Treated HEM (SGT-
HEM)
Sulfate
Total Dissolved Solids (TDS)
Total Phosphorus
Total Suspended Solids (TSS)
4500-NH3F
353.2
4500-N,C
5210B
4500-CL-C
1664A
1664A
D5 16-90
2540 C
365.3
2540 D
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
MG/L
0.340
37.0
1.36
ND (2.00)
90.0
ND (5.00)
NA
1,290
1,250
1.09
5.00
0.160
0.230
3.39
4.00
20.0
6.00
ND (5.00)
80.7
281
0.250 E
12.0 E
0.150
0.730
ND (0.100)
2.00
240
ND (5.00)
NA
1,110
2,050
0.200
15.0
0.205
4.73 E
0.785 L
ND (2.00)
60.0
10.0
ND (4.00)
494
673
0.0870
6.00
oo
       Source: [ERG, 2008bj], [ERG, 2008k], [ERG, 20081], [ERG, 2008n]
       a - The concentrations presented have been rounded to three significant figures.
       b - The ash pond effluent results represent the average of the ash pond effluent and the duplicate of the ash pond effluent analytical measurements.
       < - Average result includes at least one non-detect value. (Calculation uses the report limit for non-detected results).
       E - Sample analyzed outside holding time.
       L - Sample result between 5x and lOx blank result.
       NA - Not analyzed.
       ND - Not detected (number in parenthesis is the report limit). The sampling episode reports for each of the individual plants contains additional sampling
       information, including analytical results for analytes measured above the detection limit, but below the reporting limit (i.e., J-values).

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2007/2008 Detailed Study Report               Chapter 3 - Overview of the Coal-Fired Steam Electric Industry


3.2.3   Ash Sluice Treatment Systems

       Fly ash sluice and bottom ash sluice are typically treated in large settling pond systems.
For plants with wet fly ash handling and wet bottom ash handling, the two sluice streams are
often commingled within the same settling pond system along with other waste streams.  For
plants with only one wet ash handling system (e.g., fly or bottom ash, but typically wet bottom
ash), the ash sluice may be treated in an ash pond; however, these pond systems typically include
other plant wastewaters.  The design and operation of ash settling ponds is comparable to that of
FGD settling ponds, which is described in Section 3.1.4.1.  Settling ponds can be an effective
means of removing TSS from ash sluice water, particularly from bottom ash sluice water, which
contains relatively dense ash particles.  Settling ponds may also be an effective means of
removing some metals from fly ash sluice water when these metals are present in particulate
form (see Section 3.2.2).  Similar to the FGD settling pond systems, EPA believes that the ash
pond systems are likely to undergo  seasonal turnover effects, as  described in Section 3.1.4.1.
Seasonal turnover of the ash pond has the potential to increase the concentration of pollutants in
the discharge during the turnover period.

       EPA compiled information regarding management techniques for fly ash and wastewater
treatment systems for fly ash sluice. Table 3-13 presents fly ash handling practices at plants
included in EPA's combined data set, which includes UWAG-provided data, site visits and
sampling data, and data request information.  As shown in Table 3-13, approximately one-third
of these plants handle the majority of their fly ash wet.  Table 3-14 shows that 95 percent of the
plants that handle any amount of fly ash wet send the fly ash sluice to settling ponds. Ninety-one
percent of the fly ash ponds from the combined data set receive both fly ash and bottom ash.
Only one of the fly ash ponds included in the combined data set  is completely segregated (i.e., it
receives only fly ash wastewater).

       More plants in the combined data set operate wet bottom ash handling systems than wet
fly ash handling systems. Twelve percent of the plants  in the combined data set operate all or a
portion of their bottom ash dry (11 plants; 20 units; 9,269 MW). Fewer wet fly ash systems are
expected because the New Source Performance Standards promulgated in 1982 prohibit the
discharge of wastewater pollutants from fly ash transport water.  Not surprisingly, EPA has
found that the steam electric units generating wet fly ash sluice tend to be older units, while dry
ash handling systems tend to be operated on newer units.

       The plants within EPA's combined data set that operate wet bottom ash handling systems
send their bottom ash sluice to hydrobins,  settling ponds, or both (see Section 3.2.1.2 for
discussion of these systems). EPA has observed that most bottom ash settling ponds also receive
other plant wastewaters.  In response to the data request, no plants reported operating segregated
bottom ash ponds.

       For all of the fly and bottom ash ponds reported in response to the data  request, waste
streams other than ash sluice ranged from  3 to 93 percent of the total pond influent flow (in
2006). The major types of influent, other than ash sluice, were various types of low-volume
wastes, cooling tower blowdown, and FGD wastewater. [U.S. EPA, 2008a]
                                          3-59

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
  Table 3-13.  Fly Ash Handling Practices at Plants Included in EPA's Combined Data Set
Fly Ash Handling
Wet-Sluiced c
Handled Dry or Removed in Scrubber d
Other - Most Ash Handled Dry or Unknown e
Total
Number of Plants a
32 (34%)
61 (65%)
8 (9%)
94
Number of
Generating Units
79 (37%)
120 (55%)
18 (8%)
217
Capacity b
30,500 (28%)
69,100(64%)
8,110(8%)
108,000
Source: UWAG-provided data (including planned units) [ERG, 2008f], data request information (including planned
units) [U.S. EPA, 2008a], and site visit and sampling information (including planned units). EPA's combined data
set contains information on 116 out of approximately 500 coal-fired power plants, and represents about 20% of the
total coal-fired industry.  Note that all data request units (those with and without FGD systems) are included in this
data set; however, the data set presented in Table 3-3 includes only data request units associated with FGD systems.
a - Number of plants is not additive because some plants operate units with different types of fly ash handling
practices.
b - The capacities presented have been rounded to three significant figures.  Due to rounding, the total capacity may
not equal the sum of the individual capacities.  The capacities for the UWAG-provided data, data request
information, and site visit and sampling information are based on information provided to EPA and may represent
various capacities (e.g., nameplate capacity, net summer capacity, gross winter capacity, etc.).
c - Represents plants/units that handle all or almost all of their fly ash wet.
d - Represents plants/units in which ash is either handled dry (and sold or landfilled) or removed in a scrubber.
e - Represents plants/units that either handle a relatively small amount of their fly ash wet and the rest dry, or for
which the information received on fly ash handling was unclear.


   Table 3-14. Fly Ash Sluice Wastewater Treatment Systems at Plants Included in EPA's
                                        Combined Data Set




Type of Fly Ash Wastewater Treatment
System
Settling pond, commingled with bottom ash
Settling pond, NOT commingled with bottom ash
Settling pond, not known if commingled with
bottom ash
Other (trucked away, no wastewater)
Total




Number of
Plants
21 (57%)
3 (8%)
11 (30%)
2 (5%)
37



Number of
Generating
Units
64 (66%)
6 (6%)
25 (26%)
2 (2%)
97




Capacity
(MW)a
22,200 (58%)
5,360 (14%)
10,200 (26%)
747 (2%)
38,600
Number of
Treatment
Systems That
Also Receive
FGD
Wastewater
4
1
2
0
7
Source: UWAG-provided data (including planned units) [ERG, 2008f], data request information (including planned
units) [U.S. EPA, 2008a], and site visit and sampling information (including planned units). EPA's combined data
set contains information on 116 out of approximately 500 coal-fired power plants, and represents about 20% of the
total coal-fired industry.  Note that this table represents the plants/units from Table 3-13 that handle any amount of
fly ash wet (i.e., the "Wet-sluiced" and "Most Ash Handled Dry" plants/units).
a - The capacities presented have been rounded to three significant figures. Due to rounding, the total capacity may
not equal the sum of the individual capacities.  The capacities for the UWAG-provided data, data request
information, and site visit and sampling information are based on information provided to EPA and may represent
various capacities (e.g., nameplate capacity, net summer capacity, gross winter capacity).
                                                 3-60

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2007/2008 Detailed Study Report
Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
3.3    Coal Piles

       Coal-fired power plants typically receive the coal via train or barge; however, depending
on the location of the mine, trucks could also transport the coal to the plant.  The coal is
unloaded in a designated area and conveyed to an outdoor storage pile, known as a coal pile.
Power plants generally store between 25 and 35 days worth of coal in the coal pile, but this
varies by plant.  Some coal-fired plants may operate more than one coal pile depending on the
location  of the boilers and whether different types of coal are used or blended.

3.3.1  Coal Pile Runoff Generation

       Rainwater contacting the coal pile generates a waste stream that contains pollutants
associated with the coal, referred to as coal pile runoff. The quantity of runoff depends upon the
amount of rainfall, the physical location and layout of the pile, and the absorption of water under
the pile.  The amount of contaminants generated depends upon the coal characteristics and the
residence time of water within the coal pile.

3.3.2  Coal Pile Runoff Characteristics

       As described in Section 3.3.1, the quantity of coal pile runoff generated depends upon the
size, location, and layout of the coal pile, the absorption of water under the pile, and the amount
of rainfall at the plant. Coal pile runoff is intermittently transferred to a coal pile runoff pond
(only during or immediately after times of rainfall).  Table 3-15 presents the estimated  coal pile
runoff flow rates reported in the data request responses.  Most of the flow rates in Table 3-15
were estimated by the plants based on the amount of rainfall at the plant, the size of the coal pile,
and a runoff coefficient (based on plant experiences).  The flow rates that are normalized on a
MW basis are based on the  plants' total coal-fired capacity. The average coal-fired capacity per
plant is 1,490 MW and the median coal-fired capacity per plant is 1,300 MW.

       Table 3-15. Coal Pile Runoff Generation from EPA Data Request Responses

DPY/plantb
Number of Plants
30
Average a
133
Median a
124
Range a
40 - 365
Flow Rate per Plant
GPY/plant
30
31,100,000
17,600,000
2,070,000 -
364,000,000
Flow Rate Normalized by Coal-Fired Capacity
GPY/MW c
30
19,300
12,600
2,650 - 109,000
Flow Rate Normalized by Tons of Coal Burned
GPY/TonofCoal
30
6.61
5.20
1.25-26.2
Source: [U.S. EPA, 2008a]
Note: The coal pile runoff flow rate is dependent on the geographic location of the plant (determines the amount of
rainfall), the capacity of the plant, and the amount of coal reserve at the plant (determines the size of the pile).
a - The flow rates presented have been rounded to three significant figures.
b - Estimated number of days coal pile runoff wastewater was generated in 2006.
c - For this summary, EPA assumed that the total capacity for each coal-fired steam electric unit is associated with
coal use. Non-coal-fired units are not included in the capacity calculations.
                                            3-61

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2007/2008 Detailed Study Report              Chapter 3 - Overview of the Coal-Fired Steam Electric Industry
       The rainfall generating the coal pile runoff can dissolve inorganic salts or cause chemical
reactions in the coal piles, which will be carried away in the runoff.  Coal pile runoff may
contain high concentrations of copper, iron, aluminum, nickel, and other constituents present in
coal [U.S. EPA, 1982]. Plants typically direct coal pile runoff wastewaters to a holding pond
along with stormwater runoff from other areas near the coal pile.  This section does not present
pollutant concentration data for coal pile runoff because EPA has not sampled a coal pile runoff
waste stream.

3.3.3  Coal Pile Runoff Treatment Systems

       Coal pile runoff is typically treated in settling ponds, as mentioned  in Section 3.3.2.
Based on information received in response to the data request, coal pile runoff ponds are more
likely to be segregated than ash ponds.  Of the 15 coal pile runoff ponds reported in the data
request responses (categorized as coal pile runoff ponds because they do not receive any ash
sluice), all but two ponds receive only (or essentially only)  coal pile runoff. As is the case for
ash settling ponds, coal pile runoff ponds are typically designed for TSS removal. Each of the 15
data request coal pile runoff ponds was reported to be designed for TSS removal. In addition,
some plants reported that the ponds were also designed to meet pH targets  and three were
reported to be designed for metals removal; however, the plants do not appear to be performing
any specific treatment for metals removal (i.e., none of the plants reported  any chemical addition
to the ponds).

       During EPA's site visits and  sampling program, EPA determined that many of the plants
operating  segregated coal pile runoff ponds collect and store the runoff in ponds until the pond is
at a level that could overflow. At that point, the plant either discharges the coal pile runoff to
surface waters or commingles the coal pile runoff with other wastewater (e.g., transferred to ash
pond system) prior to discharge.
                                           3-62

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2007/2008 Detailed Study Report                                           Chapter 4 - References
4.     REFERENCES

Aquatech. 2006. Telephone conversation with Manoj Sharma of Aquatech and TJ. Finseth of
Eastern Research Group, Inc.  "Aquatech Boron Mitigation System." (11 April). DCN 03639.

Babcock & Wilcox Company. 2005. Steam: Its Generation and Use.  41st edition. Edited by
J.B. Kitto and S.C. Stultz. Barberton, Ohio. DCN 05759.

Eastern Research Group, Inc. (ERG). 2007a.  Memorandum to Ron Jordan, US EPA. "Notes
from Site Visit at Tampa Electric Company's Big Bend Station on April 27, 2007." (24 May).
DCN 04728.

Eastern Research Group, Inc (ERG). 2007b.  Final Generic Sampling and Analysis Plan for
Coal-Fired Steam Electric Power Plants .  (1 June). DCN 04296.

Eastern Research Group, Inc (ERG). 2007c.  Sampling Plan, Wisconsin Electric Power
Company's Pleasant Prairie Power Plant.  (14 June). DCN 04298.

Eastern Research Group, Inc (ERG). 2007d.  Final Engineering Site Visit Report for Georgia
Power's Plant Yates. (27 June).  DCN 04301.

Eastern Research Group, Inc (ERG). 2007e.  Final Engineering Site Visit Report for Georgia
Power's Plant Wansley. (27 June).  DCN 04302.

Eastern Research Group, Inc (ERG). 2007f.  Sampling Plan, Tampa Electric Company's Big
Bend Station. (10 July). DCN04815A1.

Eastern Research Group, Inc (ERG). 2007g.  Final Engineering Site Visit Report for Tennessee
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Eastern Research Group, Inc (ERG). 2007h.  Engineering Site Visit Report for EME Homer
City Generation L.P.'s Homer City Power Plant.  (09 August). DCN 04718.

Eastern Research Group, Inc (ERG). 2007L  Sampling Plan, EME Homer City Generation L.P.'s
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Eastern Research Group, Inc (ERG). 2007J.  Sampling Plan, Tennessee Valley Authority's
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Eastern Research Group, Inc (ERG). 2007k.  Final Engineering Site Visit Report for Reliant
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Eastern Research Group, Inc (ERG). 20071. Memorandum to Ron Jordan: Addendum to the
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Eastern Research Group, Inc (ERG). 2007m.  Sampling Plan, Ohio Power Company's Mitchell
Plant. (09 October). DCN05912A1.

                                         4-1

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2007/2008 Detailed Study Report                                          Chapter 4 - References
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Cardinal Power Plant. (09 October). DCN05917A1.

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Eastern Research Group, Inc (ERG). 2008b. Coal-Fired Power Plants Expected to be Operating
Wet FGD Scrubber Systems by 2020. (14 July). DCN 06168.

Eastern Research Group, Inc (ERG). 2008c. Memorandum to Ron Jordan, EPA. "Meeting
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Eastern Research Group, Inc (ERG). 2008d. Memorandum to Ron Jordan, EPA. "Model Plant
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Eastern Research Group, Inc. (ERG). 2008e. Memorandum to Public Record for the Effluent
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Eastern Research Group, Inc. (ERG). 2008f.  Memorandum to Public Record for the Effluent
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Eastern Research Group, Inc. (ERG). 2008g. Final Site Visit Notes for Duke Energy Carolina's
Belews Creek Steam  Station (Non-CBI).  (19 August).  DCN 06145.

Eastern Research Group, Inc. (ERG). 2008h. Final Site Visit Notes for Duke Energy Carolina's
Marshall Steam Station.  (19 August).  DCN 06143.

Eastern Research Group, Inc. (ERG). 2008L  Memorandum to Ron Jordan and Ahmar Siddiqui,
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Eastern Research Group, Inc (ERG). 2008J.  Final Sampling Episode Report, EME Homer City
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Eastern Research Group, Inc (ERG). 2008k. Final Sampling Episode Report,  Ohio Power
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Eastern Research Group, Inc (ERG). 2008m. Final Sampling Episode Report, Tampa Electric
Company's Big Bend Station. (August).  DCN 05816.


                                        4-2

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2007/2008 Detailed Study Report                                            Chapter 4 - References
Eastern Research Group, Inc (ERG). 2008n. Final Sampling Episode Report, Tennessee Valley
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                                         4-3

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2007/2008 Detailed Study Report                                           Chapter 4 - References
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2007/2008 Detailed Study Report                                            Chapter 4 - References
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                                          4-5

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2007/2008 Detailed Study Report                                            Chapter 4 - References
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