## MEMORANDUM

DATE: October 20 , 201 2

SUBJECT: Effluent Limitations for FGD Wastewater, Gasification Wastewater, and Combustion Residual Leachate for the Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Rulemaking

FROM: Cuc Schroeder , USEPA

TO: Ronald Jordan , USEPA

Cc: John Rogers, Westat

This report presents the results of the statistical analyses performed on the Flue Gas Desulfurization ( FGD ) and g asification wastewater treatment data and the resulting long

- term

average s , variability factors, and effluent limitation s

. The treatme nt technology options for FGD

wastewater presented in this report are: (i) one

- stage chemical precipitation system employi ng both hydroxide and sulfide precipitation and iron coprecipitation (hereafter referred to as “chemical precipitation”) , (ii) biological ( one

- stage chemical precipitation employing both hydroxide and sulfide precipitation and iron coprecipitation followed by anoxic/anaerobic biological treatment , hereafter refe rred to as “biological ”. ), and (iii) chemical precipitation followed by vapor

- compression evaporation system (hereafter referred to as “vapor

compression evaporator”

. The treatment technology option for gasification wastewater is

vapor

- compression evaporation system

. See the Technical Development Document for the Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (hereafter referred t o in this document as Techn ical Development Document) for a detailed desc ription of the FGD and gasification systems and the wastewater
associated with each waste stream

, rationale for selecting plants used in the calculation of the
effluent limitations fo r each technology option, and pollutants that are proposed for regulation
for each technology option

.

The following bullets summarize the plants from which data were used to calculate the
limits for each technology option for FGD wastewater together with the poll utants that are proposed for regulation:

**•** The effluent limitations for c hemical precipitation technology option are based on data
from Hatfield’s Ferry, Keystone, and Miami Fort

. The polluta nts proposed to be regulated for this technology option are arsenic and mercury

.

**•** The effluent limitations for b iological technology option are based by Allen and Belews
Creek

. The pollutants proposed to be regulated for this technology option are arsenic, mercury, nitrate

- nitrite as N, and selenium

. While these two plants operate the biological treatment system used as the basis for the technology option, neither of

### Page 2 

### these plants include sulfide precipitation in the upstream chemical precipitation system

. F or this reason, EPA is transferring the arsenic and mercury limitation s calculated based
on the chemical precipitation treatment to the biological treatment for FGD wastewater (see Section 13 of the Technical Development Document for a detailed discussion of the
transfer of limitation s).

**•** The effluent limitations for v apor

- compression evaporation technology option are based

on Brindisi

. The pollutants proposed to be regulated for this technology option are arsenic, mercury, selenium, and total dissolved sol ids.

The following bullets summarize the plants from which data we re used to calculate the
effluent limitations for gasification wastewater together with the poll utants that are proposed for regulation:

**•** The effluent limitations for v apor

- compression evaporation technology option are based

on Polk and Wabash River

. The pollutants proposed to be regulated for this technology option are arsenic, mercury, selenium, and total dissolved solids.

In addition to the technology options for FGD and gasification wastewaters discussed in the previous paragraphs, EPA is also proposing to establish effluent limitation s for combustion
residuals leachate (hereafter referred to as leachate) at certain facilities based on chemical precipitation technology option

. The e ffluent limitations for leach ate are based on the transfer
of the effluent limitation s calculated for the chemical precipitation technology option for FGD

wastewater because EPA does not have available data for chemical precipitation treatment of
leachate

. This transfer of effluent limitation s is appropriate because the pollutants in leachate are similar to those in FGD wastewater except at lower concentrations

. See Section 13 of the Technical Development Document for a detailed discussion of the transfer of limitation s.

Section 1 of this report provides an overview of the document

. Section 2 provides a brief description of the available data u sed to develop the effluent limitation s for each technology option. Section 3 describes the data correction s, excl usions, baseline substitutions , and aggregation made to the data before calculating the effluent limitation s . S ection 4 describes the data editing procedure s used to s elect datasets for developing the effluent limitation s for each pollutant at each plant

. Section 5 provides the statistical methodology used to calculate the
effluent limitation s together with the long

- term average and variability factors

. Sections 6, 7

, and 8 contain a detailed summary of th e data together with the effluent limitation s for ea ch pollutant in each treatment technology option for FGD wastewater

. Section 9 contains a detailed summary of the data together with the effluent limitation s f or each pollutant for the gasification wastewater treatment technology option

. Section 10 present s the overall summary
of the long

- term average, variability factors, and effluent limitation s for each pollutant in each technology option. Section 11 provides a discussion of the engineering review of the effluent
limitation s to verify that the limitation s are reasonable based upon the design and expected operation of the control technologies

.

### Page 3 

### In addition to the eleven sections described above, four appendices are attached to the
report. Appendix 1 contains a list of the data that were corrected due to entry errors and all the data that were excluded for various reasons. Appendix 2 contains longitudinal plots (along with smoothed curves superimposed over the data) for the plant self

- monitoring data that EPA used to aid in determining the start

- up or init ial commissioning period for the treatment system for
Allen and Belews Creek

. Appendix 3 contains a summary of the results of the data editing criteria (i.e., long

- term average test)

. Appendix 4 contains a summary of the results of the engineering review o f the limitation s.

### Page 4 

## Table of Contents

1. Introduction

................................ ................................ ................................ ................................ ............ 14

2. Description of Data Used to Calculate Long

- Term Averages, Variability Factors, and Effluent Limits

... 14

2.1. Overview of the Data

................................ ................................ ................................ ....................... 15 2.2. Analytical Methods

................................ ................................ ................................ .......................... 15 2.3. Combining Data from Multiple Sources within a Plant

................................ ................................ .... 16

3. Data Corrections, Exclusions, Baseline Substitutions, and Aggregation

................................ ................. 16

3.1. Data Corrections

................................ ................................ ................................ .............................. 17
3.2. Data Exclusions and Rationale for the Exclusions

................................ ................................ ............ 17 3.2.1. Excluding mercury samples analyze d using an insufficiently

- sensitive analytical method

...... 17 3.2.2. Excluding samples collected during the initial commissioning period for the treatment
system

................................ ................................ ................................ ................................ ..... 18 3.2.3. Excluding analytical results that were identified as questionable due to quality control (QA/QC ) issues, abnormal conditions or treatment upset, or were analytical anomalies

..... 19
3.3. Baseline Substitutions

................................ ................................ ................................ ...................... 21 3.4. Data Aggregation

................................ ................................ ................................ ............................. 23 3.4.1. Aggregation of field duplicates

................................ ................................ ................................ . 23 3.4.2. Aggregation of overlapping samples

................................ ................................ ........................ 24

4. Data Editing Criteria

................................ ................................ ................................ ................................ 24

5. Statistical Methodolo gy

................................ ................................ ................................ .......................... 25

5.1. Definitions and Background

................................ ................................ ................................ ............. 25
5.2. Statistical Model Selected for the Data

................................ ................................ ........................... 26 5.3. Autocorrelation Analysis

................................ ................................ ................................ .................. 26 5.4. Dataset Requirement

................................ ................................ ................................ ....................... 28 5.5. Calculating Effluent Limits for Each Pollutant in Each Technology Option

................................ ...... 28 5.6. Special Case

– Effluent Limits Based on Detection Limits

................................ ................................ 29

6. Treatment Technology Option for FGD Wastewater: Chemical Precipitation

................................ ....... 29

6.1. Chemical Precipitat ion Treatment for FGD Wastewater: Arsenic

................................ ................... 31 6.1.1. Longitudinal plots of the data for arsenic (ug/L)

................................ ................................ ...... 31 6.1.2. Summary statistics for arsenic (ug/L)

................................ ................................ ....................... 31
6.1.3. Plant

- specific long

- term averages and variability factors, option long

- term average and variability factors, and effluent limits for arsenic (ug/L)

................................ ......................... 32 6.2. Chemical Precipitation Treatment for FGD Wastewater: Mercury

................................ ................. 33 6.2.1. Longitudinal plots of the data for mercury (ng/L)

................................ ................................ .... 33 6.2.2. Summary statistics for mercury (ng/L)

................................ ................................ ..................... 33
6.2.3. Plant

- specific Long

- term averages and variability factors, option long

- term average and variability factors, and effluent limits for mercury (ng/L)

................................ ....................... 34 6.3. Chemical Precipitation Treatment for FGD Wastewater: Summary of the Option Long

- Term Averages, Option Variability Factors, and Effluent Limits

................................ ............................... 34

7. Treatment Technology Option for FGD Wastewater: Biological Treatment

................................ .......... 35

7.1. Biological Treatment for FGD Wastewater: Arsenic

................................ ................................ ........ 36

### Page 5 7.1.1. Longitudinal plots of the data for arsenic (ug/L)

................................ ................................ ...... 36 7.1.2. Summary statistics for arsenic (ug/L)

................................ ................................ ....................... 37 7.2. Biological Treatment for FGD Wastewater: Mercury

................................ ................................ ...... 38 7.2.1. Longitudinal plots of the data for mercury (ng/L)

................................ ................................ .... 38 7.2.2. Summary statistics for mercury (ng/L)

................................ ................................ ..................... 39 7.3. Biological Treatment for FGD Wastewater: Nitrate

- nitrit e as N

................................ ...................... 39 7.3.1. Longitudinal plots of the data for nitrate

- nitrite as N (mg/L)

................................ ................... 39 7.3.2. Summary statistics for nitrate

- nitrite as N (mg/L)

................................ ................................ .... 40
7.3.3. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and effluent limits for nitrate

- nitrite as N (mg/L)

................................ ..... 40 7.4. Biological Treatment for FGD Wastewater: Selenium

................................ ................................ ..... 41 7.4.1. Longitudinal plots of the data for selenium (ug/L)

................................ ................................ ... 41 7.4.2. Summary statistics for selenium (ug/L)

................................ ................................ .................... 42
7.4.3. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and effluent limits for selenium (ug/L)

................................ ...................... 43 7.5. Biological Treatment for FGD Wastewater: Summary of the Option Long

- Term Averages, Variability Factors, and Effluent Limits

................................ ................................ ............................ 43

8. Treatment Technology Option for FGD Wastewater: Vapor

- Compression Evaporation System

........... 44

8.1. Vapor

- Compression Evaporation for FGD Wastewater: Arsenic

................................ ..................... 45 8.1.1. Longitudinal plots of the data for arsenic (ug/L)

................................ ................................ ...... 45 8.1.2. Summary statistics for arsenic (ug/L)

................................ ................................ ....................... 45
8.1.3. Plant

- specific long

- term averages and variability fac tors, option long

- term averages and variability factors, and effluent limits for arsenic (ug/L)

................................ ......................... 46 8.2. Vapor

- Compression Evaporation for FGD Wastewater: Mercury

................................ ................... 47 8.2.1. Longitudinal plots of the data for mercury (ng/L)

................................ ................................ .... 47 8.2.2. Summary statistics for mercury (ng/L)

................................ ................................ ..................... 48
8.2.3. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and effluent limits for mercury (ng/L)

................................ ....................... 48 8.3. Vapor

- Compression Evaporation for FGD Wastewater: Selenium

................................ .................. 49 8.3.1. Longitudinal plots of the data for selenium (ug/L)

................................ ................................ ... 49 8.3.2. Summary statistics for selenium (ug/L)

................................ ................................ .................... 49
8.3.3. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and effluent limits for selenium (ug/L)

................................ ...................... 50 8.4. Vapor

- Compression Evaporation for FGD Wastewater: Total Dissolved Solids (TDS)

..................... 51 8.4.1. Longitudinal plots of the data for TDS (mg/L)

................................ ................................ .......... 51 8.4.2. Summary statistics for TDS (mg/L)

................................ ................................ ............................ 51
8.4.3. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and effluent limits for TDS (mg/L)

................................ ............................. 52 8.5. Vapor

- Compression Evaporation for FGD Wastewater: Summary of the Option Long

- Term Averages, Option Variability Factors, and Effluent Limits

................................ ............................... 52

9. Treatment Technology Option for Gasification Wastewater: Vapor

- Compression Evaporation

........... 54

9.1. Vapor

- Compression Evaporation for Gasification: Arsenic

................................ .............................. 55 9.1.1. Longitudinal plots of the data for arsenic (ug/L)

................................ ................................ ...... 55 9.1.2. Summary statistics for arsenic (ug/L)

................................ ................................ ....................... 55
9.1.3. Plant

- specific long

- term average and variability factors, option long

- term average and variability factors, and effluent limits for arsenic (ug/L)

................................ ......................... 56

### Page 6 9.2. Vapor

- Compression Evaporation for Gasification: Mercury

................................ ............................ 57 9.2.1. Longitudinal plots of the data for mercury (ng/L)

................................ ................................ .... 57 9.2.2. Summary statistics for mercury (ng/L)

................................ ................................ ..................... 57
9.2.3. Plant

- specific long

- term average and variability factors, option long

- term average and variability factors, and effluent limits for mercury (ng/L)

................................ ....................... 58 9.3. Vapor

- Compression Evaporation for Gasification: Selenium

................................ .......................... 59 9.3.1. Longitudinal plots of the data for selenium (ug/L)

................................ ................................ ... 59 9.3.2. Summary statistics for selenium (ug/L)

................................ ................................ .................... 60
9.3.3. Plant

- specific long

- term averages and variability factors, option long

- term average and variability factors, and effluent limits for selenium (ug/L)

................................ ...................... 61 9.4.1. Longitudinal plots of the data for TDS (mg/L)

................................ ................................ .......... 61 9.4.2. Summary statistics for TDS (mg/L)

................................ ................................ ............................ 62
9.4.3. Plant

- specific long

- term averages and variability factors, option long

- term average and variability factors, and effluent limits for TDS (mg/L)

................................ ............................. 63 9.5. Vapor

- Compression Evaporation for Gasification: Summary of the Option Long

- Term Average, Option Variability Factors, and Effluent Limits

................................ ................................ ................ 63

10. Summary of Effluent Limits for Each Treatment Technology Option for FGD, Gasification, and

Leachate Wastewater

................................ ................................ ................................ ........................... 64

11. Engineering Review of the Effluent Limits

................................ ................................ ............................ 66

11.1. Comparison of the Limits to Effluent Data Used as the Basis for the Limits

................................ . 66 11.2. Comparison of the Effluent L imits to Influent Data

................................ ................................ ....... 71

APPENDIX 1: List of All Observations that Were Corrected and Excluded Before Calculating the Limits

.. 72

1. Corrections Made to Plant Self

- Monitoring Data from Belews Creek

................................ ................ 73 2. List of Data Excluded Due to Samples Analyzed Using an Insufficiently

- Sensitive Analytical
Method

................................ ................................ ................................ ................................ ............ 74 3. List of Data Excluded Due to Samples Being Collected During the Initial Commissioning Period for the Treatment System

................................ ................................ ................................ ............... 76 4. List of Data Excluded Due to Analytical Results that Identified as Questionable Due to the Quality Control Issues, Abnormal Conditions or Treatment Upset, or Analytical Anomalies

......... 76

APPENDIX 2: Plots of Plant Self

- monitoring Data with Smoothed Curves to Aid in Determining Initial Commissioning Period of Treatment System

................................ ................................ ....................... 80

APPENDIX 3: Data Editing Criteria Results

................................ ................................ ................................ .. 87

APPENDIX 4: Summary of the Results for the Engineering Review of the Limits

................................ ....... 90

1. Results of the Comparison of the Limits to Effluent Data Used as the Basis for the Limits

............... 91 2. Comparison of the Effluent Limits to Influent Data

................................ ................................ ............ 94

### Page 7 

## List of Tables

Table 1. Summary of the analytical lab methods used for each pollutant.

................................ ................ 16

Table 2. Summary of the base line values used for each pollutant.

................................ ............................ 22

Table 3. Aggregation of Field Duplicates.

................................ ................................ ................................ ... 24

Table 4. Summary of Estimated Autocorrelation Values at Allen and Belews Creek.

................................ 27

Table 5. Numbers of detected and non

- detected observations and sample

- specific detection limits for arsenic (ug/L) by plant and sampling location.

................................ ................................ ... 32

Table 6. Summary statistics of arsenic concentration (ug/L) for all detected and non

- detected
samples combined, by plant and sampling location.

................................ ................................ 32

Table 7. Plant

- specific long

- term averages and variability factors, option long

- term average and variability factors, and limits for arsenic (ug/L) at chemical precipitation effluent.

................ 33

Table 8. Summary statistics of mercury concentration (ng/L) for all detected samples by plant and
sampling location.

................................ ................................ ................................ ..................... 34

Table 9. Plant

- specific long

- term average and variability factors, option long

- term average and variability factors, and limits for mercury (ng/L) a t chemical precipitation effluent.

.............. 34

Table 10. Summary of option long

- term averages, option variability factors, and effluent limits for chemical precipitation FGD wastewater treatment technology.

................................ ............. 34

Table 11. Numbers of detected and non

- detected observation s and sample

- specific detection limits for arsenic (ug/L) by plant and sampling location.

................................ ................................ ... 37

Table 12. Summary statistics of arseni c concentration (ug/L) for all detected and non

- detected
samples combined, by plant and sampling location.

................................ ................................ 38

Table 13. Summary stat istics of mercury concentration (ng/L) for all detected and non

- detected samples combined by plant and sampling location.

................................ ................................ . 39

Table 14. Number of detected, non

- detected, and sample

- specific detection limits for nitrate

- nitrate as N (mg/L) by plant and sampling location.

................................ ................................ ............ 40

Table 15. Summary statistics of nitrate

- nitrite as N concentration (mg/L) for all detected and

non

- detected samples combined by plant and sampling location.

................................ .......... 40

Table 16. Lag

- 1 autocorrelation values, plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and limits for nitrate

- nitrite as N (mg/L)

at bioreactor effluent.

................................ ................................ ................................ ............... 41

### Page 8 Table 17. Number of detected, non

- detected, and sample

- specific detection limits for selenium (ug/L) by plant and sampling locatio n.

................................ ................................ ..................... 42

Table 18. Summary statistics of selenium concentration (ug/L) for all detected and non

- detected samples combined by plant and sampling location.

................................ ................................ . 42

Table 19. Lag

- 1 autocorrelation values, plant

- specific long

- term averages and variability factors,
option long

- term averages and variability factors, and limits for selenium (ug/L) at

bioreactor effluent.

................................ ................................ ................................ ................... 43

Table 20. Summary of option lo ng

- term averages, variability factors, and effluent limits for biological FGD wastewater treatment technology.

................................ ................................ .................. 44

Table 21. Numbers of detected and non

- detected observations and sample

- specific detection limits for arsenic (ug/L) by sampling location.

................................ ................................ .................... 46

Table 22

. Summary statistics of arsenic concentration (ug/L) for all detected and non

- detected
samples combined by sampling location.

................................ ................................ ................. 46

Table 23

. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and limits for arsenic (ug/L) at brine concentrator distillate and
crystallizer condensate.

................................ ................................ ................................ ............ 47

Table 24. Summary statistics of mercury concentration (ng/L) for all detected and non

- detected
samples combined by sampling location.

................................ ................................ ................. 48

Table 25. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and limits for mercury (ng/L) at brine concent rator distillate and crystallizer condensate.

................................ ................................ ................................ ............ 48

Table 26. Number of detected, non

- detected, and sample

- specific detection limits f or selenium (ug/L) by sampling location.

................................ ................................ ................................ ...... 49

Table 27. Summary statistics of selenium concentration (ug/L) for all detected and non

- detected
samples combined by sampling location.

................................ ................................ ................. 50

Table 28. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and limits for selenium (ug/L) at brine concentrator distillate and
crystallizer condensate.

................................ ................................ ................................ ............ 50

Table 29. Number of detected, non

- detected, and sample

- specific detection limits for total dissolved solid (mg/L) by sampling location.

................................ ................................ ............................ 51

Table 30. Summary statistics of total dissolved solids concentration (mg/L) for all detected and non

detected samples combined by sampling location.

................................ ................................ .. 52

### Page 9 Table 31. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and limits for TDS (mg/L) at brine concentrator distillate and
crystallizer condensate.

................................ ................................ ................................ ............ 52

Table 32. Summary of option long

- term averages, variability factors, and limits for vapor

compression evaporation technology for FGD wastewater at brine concentrator distillate.

.. 53

Table 33. Summary of option long

- term averages, option variability factors, an d limits for mechanical vapor

- compression evaporation technology for FGD wastewater at crystallizer condensate.

................................ ................................ ................................ ............ 53

Table 34

. Number s of detected and non

- detected observations and sample

- specific detection limits for arsenic (ug/L) by plant and sampling location.

................................ ................................ ... 56

Table 35. Summary statistics of arsenic concentration (ug/L) for all detected and non

- detected
samples combined, by plant and sampling location.

................................ ................................ 56

Table 36. Plant

- specific long

- term average and variability factors, option long

- term average and variability factors, and limits for arsenic (ug/L) at vapor compression

evaporator condensate.

................................ ................................ ................................ ............ 57

Table 37. Numbers of detected and non

- detected observations and sample

- specific detection limits for mercury (ng/L) by plant and sampling location

. ................................ ................................ . 58

Table 38. Summary statistics of mercury concentration (ng/L) for all detected and non

- detected
samples combined, by plant and sampling location.

................................ ................................ 58

Table 39. Plant

- specific long

- term average and variability factors, option long

- term average and variability f actors, and limits for mercury (ng/L) at vapor compression evaporator

condensate.

................................ ................................ ................................ ............................... 59

Table 40. Numbers of detected and non

- detected observations and sample

- specific detection limits for selenium (ug/L) by plant and sampling location.

................................ ................................ 60

Table 41. Summary statisti cs of selenium concentration (ug/L) for all detected and non

- detected samples combined, by plant and sampling location.

................................ ................................ 60

Table 42 . Plant

- specific long

- term averages and variability factors, option long

- term average and variability factors, and limits for selenium (ug/L) at vapor compression evaporator

condensate.

................................ ................................ ................................ ............................... 61

Table 43. Numbers of detected and non

- detected observations and sample

- specific detection limits for TDS (mg/L) by plant and sampling location.

................................ ................................ ........ 62

Table 44. Summary statistics of TDS concentration (mg/L) for all detected and non

- detected samples
combined, by plant and sampling location.

................................ ................................ .............. 62

### Page 10 Table 45. Plant

- specific long

- term averages and variability factors, option long

- term average and variability factors, and numeric limits for TDS (mg/L) at vapo r compression evaporator

condensate.

................................ ................................ ................................ ............................... 63

Table 46. Summary of option long

- term averages, option variability factors, and limits for vapor

compression evaporation technology for gasification wastewater.

................................ ........ 63

Table 47. Summary of the option long

- term averages and var iability factors together with the effluent limits for each of the FGD, gasification, and leachate technology option.

................. 65

Table 1.1. Summary of the corrected detection indicators for the Belews Creek self

- monitoring data, arranged by sampling location, pollutant, and sampling date.

................................ ................ 73

Table 1.2. Summary of the data corrections for the Belews Creek self

- monitoring data, arranged by
sampling location, pollutant, and sampling date.

................................ ................................ ..... 74

Table 1.3. Summary of the mercury data excluded from plant self monitoring data due to using an insufficiently

- sensitive analytical method.

................................ ................................ ............... 75

Table 1.4. Summary of the questionable mercury data excluded due to quality control issues for the plant self

- monitoring data at Allen and Belews Creek.

................................ ............................ 77

Table 1.5. Summary of data excluded due to abnormal conditions or treatment upset and analytical

anomalies.

................................ ................................ ................................ ................................ . 78

Table 3.1. Summary of the results for data editing procedure performed to select a dataset for
pollutant at each plant in calculating the limits.

................................ ................................ ....... 89

Table 4.1. Listing of all daily values that are above the daily limits for c hemical precipitation

treatment for FGD wastewater.

................................ ................................ ................................ 91

Table 4.2. For chemical precipitation treatment for FGD wastewater, a listin g of all the daily values that are above the monthly limits, along with any other daily values collected in the same

month.

................................ ................................ ................................ ................................ ....... 92

Table 4.3. Listing of all daily values that are above the daily limits for the biological treatment technology option for FGD wastewater.

................................ ................................ ................... 92

Table 4.4. For biological treatment for FGD wastewater, a listing of all the daily values that are above the monthly limits, along with any other daily values collected in the same month.

.............. 93

Table 4.5. Listing of all daily values that are above the daily limits for vapor

- compression evaporation treatment for gasification wastewater.

................................ ................................ .................... 94

Table 4.6. For vapor

- compression evaporation treatment for gasification wastewater, a listing of all the daily values that are above the monthly limits, along with any ot her daily values

collected in the same month.

................................ ................................ ................................ ... 94

### Page 11 Table 4.7. Summary statistics for the influent (FGD Purge) concentrations for plan ts from which the data were used as the basis for calculating the limits for chemical precipitation treatment technology option for FGD wastewater.

................................ ................................ ................... 95

Table 4.8. Summary statistics for the influent (FGD Purge) concentrations for plants from which the data were used as the basis for calculating the limits for biological treatment technology option for FGD wastewater.

................................ ................................ ................................ ...... 95

Table 4.9. Summary statistics for the influent (FGD Purge) concentrations for plants from which the

data were used as the basis for calcul ating the limits for vapor

- compression evaporation treatment technology option for FGD wastewater.

................................ ................................ . 96

Table 4.10. Summary statistics for the influent (vapor compression evaporator influent) concentrations from plants for which the data were used as the basis for calculating the limits for vapor

- compression evaporation treatment technology option for gasification

wastewater.

................................ ................................ ................................ .............................. 97

### Page 12 

## List of Figures

Figure 1. Plot of arsenic (ug/L) data on a logarithmic scale for Hatfield’s Ferry, Keystone, and Miami

Fort.

................................ ................................ ................................ ................................ ........... 31

Figure 2. Plot of mercury (ng/L) data on a logarithmic scale for Hatfield’s Ferry, Keystone, and Miami

Fort.

................................ ................................ ................................ ................................ ........... 33

Figure 3. Plot of arsenic (ug/L) data on a logarithmic scale for Allen and Belews Creek.

.......................... 37

Figure 4. Plot of mercury (ng/L) data on a logarithmic scale for Allen and Belews Creek.

........................ 38

Figure 5. Plot of nitrate

- nitrite as N (mg/L) data on a logarithmic scale for Allen and Belews Creek
(for short, the name on the vertical is labeled as nitrite)

. ................................ ........................ 39

Figure 6. Plot of selenium (ug/L) data on a logarithmic scale for Allen and Belews Creek.

....................... 41

Figure 7. Plot of arsenic (ug/L) data on a logarithmic scale for Brindisi.

................................ .................... 45

Figure 8. Plot of mercury (ng/L) data on a logarithmic scale for Brindisi.

................................ .................. 47

Figure 9. Pl ot of selenium (ug/L) data on a logarithmic scale for Brindisi.

................................ ................. 49

Figure 10. Plot of TDS (mg/L) data on a logarithmic scale for Brindisi.

................................ ...................... 51

Figure 11. Plot of arsenic (ug/L) data on a logarithmic scale for Polk and Wabash River.

......................... 55

Figure 12. Plot of mercury (ng/L) data on a logarithmic scale for Polk and Wabash River.

....................... 57

Figure 13. Plot of selenium (ug/L) data on a logarithmic scale for Polk and Wabash River.

...................... 59

Figure 14. Plot of TDS (mg/L) data on a logarithmic scale for Polk and Wabash River.

............................. 61

Figure 2.1. Plot of all self

- monitoring data for arsenic (ug/L) for Allen and Belews Creek.

....................... 81

Figure 2 .2. Smoothed plot (using LOWESS) of all self

- monitoring data for arsenic (ug/L) for Allen and

Belews Creek.

................................ ................................ ................................ ............................ 81

Figure 2.3. Plot of self

- monitoring data for arsenic (ug/L) for Allen and Belews Creek after exclusions

described in Sections 3.2.1 and 3.2.3.

................................ ................................ ...................... 82

Figure 2.4. Smoothed plot (using LOWESS) of self

- monitoring data for arsenic (ug/L) for Allen and

Belews Creek after exclusions described in Sections 3.2.1 and 3.2.3.

................................ ...... 82

Figure 2.5. Plot of all self

- monitoring data for mercury (ng/L) for Allen and Belews Creek.

..................... 83

Figu re 2.6. Smoothed plot (using LOWESS) of all self

- monitoring data for mercury (ng/L) for Allen

and Belews Creek.

................................ ................................ ................................ ..................... 83

### Page 13 Figure 2.7. Plot of self

- monitoring data for mercury (ng/L) for Allen and Belews Creek after

exclusions described in Sections 3.2.1 and 3.2.3.

................................ ................................ ..... 84

Fi gure 2.8. Smoothed plot (using LOWESS) of all self

- monitoring data for mercury (ng/L) for Allen

and Belews Creek after exclusions described in Sections 3.2.1 and 3.2.3.

............................... 84

Figure 2.9. Plot of all self

- monitoring data for selenium (ug/L) for Allen and Belews Creek.

.................... 85

Figure 2.10. Smoothed plot (using LOWESS) of all self

- monitoring data for selenium (ug/L) for Allen

and Belews Creek.

................................ ................................ ................................ ..................... 85

Figure 2.11. Plot of self

- monitoring data for selenium (ug/L) for Allen and Belews Creek after

exclusions described in Sections 3.2.1 and 3.2.3.

................................ ................................ ..... 86

Figure 2.12. Smoothed plot (using LOWESS) of self

- monitoring data for selenium (ug/L) for Allen and

Belews Creek after exclusions described in Sections 3. 2.1 and 3.2.3.

................................ ...... 86

### Page 14 

## 1. Introduction

This report presents the results of the statistical analyses performed on the Flue Gas
Desulfurization ( FGD ) wastewater and gasification wastewater treatment data and the resulting long

- term average, variability factors, and effluent limit ation s for each pollutant in each technology option.

This report is focused primarily on the summary of the data and the development of
lon g

- term averages, variability factors, and effluent limit ation s

. Thus, this report does not include a description of (i) FGD and gasification systems and the wastewater associated with each waste stream, (ii) all available treatment technology options for e ach waste stream, (iii)
the rationale for selecting plants used in the calculation of the effluent limitations for each technology option , (iv) the rationale for transferring limit ation s for dif ferent technology options, or ( v) a discussion of the baseline values used for adjusting the data before calculating
the effluent limit ation s

. For detailed discussion of the items mentioned above, see the Technical Development Document.

In this document, for simplicity, t he proposed effluent limitations guidelines and
standards are referred to as “limits”

. The terms option long

- term average s and option
variabilit y factors refer to the technology options rather than the regulatory options described in Section 8 of the Technical Development Document

. T he term “detecte d” refers to analytical results measured and reported above the sample

- spe cific quantitation limit (QL); and the term
“non

- detected” refers to values that are below the method detection limit (MDL) and those values measured by the laboratory as being betwe en the MDL and the QL in the original data (before adjusting for baseline)

. The long

- term average s , variability factors, and effluent limits
were calculated out to five decimal points for accuracy

. However, to simplify the presentation the values presented in this document have been rounded to three decimal points

. A ll exclusions, baseline substitutions, and aggregation of data were made prior to performing the statistical analyses presented in Sections 6, 7, 8, and 9

. Finally, the Excel Spreadsheet titled

“ Sampling Data Used as the Basis for Effluent Limitations for the Steam Electric Rulemaking ” contains the listing of all the available data, the excluded data, the baseline values for each pollutant, and the final concentration values that were used in th e limit calculations, a mong other relevant data items

. This Excel Spreadsheet is in the record as DCN SE02002 (this spreadsheet will hereafter be referred to as DCN SE02002 ).



## 2. Description of Data Used to Calculate Long

- Term Averages, Variability

Facto rs, and Effluent Limits

This section provides an overview of the available data at each plant selected as the
basis for the effluent limits for each technology option , the analytical methods used to analyze each of the pollutants, and the rationale for co mbining sampling data from multiple sources at each plant into a single dataset for the plant.

### Page 15 

### 2.1. Overview of the Data

In developing the effluent limits for the FGD and gasification wastewater treatment technologies, EPA used data fro m the following eight power plants : Allen, Belews Creek,
Hatfield’s Fe rry, Keystone, Miami Fort, Brindisi , Polk, and Wabash River

. The following bullets provide a brief overview of the data source available for each plant (see Sections 6, 7, 8, and 9
for a more detailed d escription of the data at each of the plants):

**•** At Hatfield’s Ferry, Keystone, and Miami Fort, sampling data were available from two

sources: (i) EPA sampling episodes (hereafter referred to as “EPA sampling”) and (ii) EPA directed sampling through letters issued under authority of CWA section 308 (here after
referred to as “CWA 308 sa mpling”)

. The data were collected at two sampling locations: FGD purge and chemical precipitation effluent

.

**•** At Allen and Belews Creek, sampling data were available from three sources: (i) plant
self monitoring (he reafter referred to as “plant self

- monitoring”) data for several years of operation provided by Duke Energy

, (ii) EPA sampling , and (iii) CWA 308 sampling

. The data were collected at three samplin g locations: FGD purg e, bioreactor influent , and
bioreactor effluent.

**•** At Brindisi, the sampling data available were from EPA sampling. The data were
collected at three s ampling locations: FGD purge, brine concentrator distillate, and crystallizer condensa te

.

**•** At P olk and Wabash River, the sampling data available were from CWA 308 sampling

. For Polk, the data were collected at four sampling locations: neutralized weak acid waste stream, vapor compression evaporator influent, vapor compression evaporator condensate, and forced circulation evaporator condensate

. For Wabash River, the sampling data were collected at four sampling locations: sour water treatment influent, steam stripper effluent, vapor compression evaporator influent, and vapor compression

ev aporator condensate.

2. 2 . Analytical Methods

The table below summarizes the analytical methods used to analyze each pollutant

. Note that the footnote in the table does not apply to the arsenic and selenium self

- monitoring
data at Allen and Belews Creek p lant s since analytical method 200.8 was use d to analyze data
from all sampling locations.

### Page 16 

### Table 1

. Summary of the analytical lab methods used for each pollutant.
Analytical method Pollutant

200.8, 6020 Arsenic 1 , Selenium 1

1631E, FGS

– 069 Mercury 2

353.2 Nitrate

- nitrite as N

2540C Total Dissolved Solids

1: Method 200.8 was used at each of the sampling locations except for FGD purge (this applies to all data except plant self

monitoring at Allen and Belews Creek)

. At FGD purge, a combination of methods 200.8 and 6020 was used since the analysis procedure was “calculated total” instead of “total”.

2: Method 1631E was used at each of the sampling locations except for FGD purge

. At FGD purge, a combination of methods
1631E and FGS

- 069 was used since the analysis procedure was “calculated total” instead of “total”.



### 2. 3 . Combining Data from Multiple Sources within a Plant

Typically, if sampling data from a plant were collected over two or more distinct time periods, EPA analyzes the data from each time period separately

. In past E ffluent L imitations
Guidelines and Standards , EPA has analyzed data as if each time period represents a different plant since these data can represent different operating conditions due to changes in management, personnel, and procedures

. On the other hand, when EPA obtains the data (such as EPA sampling and plant self

- monitoring data) from a plant during the same time period, EPA usually combines the data from these sources into a single dataset for the plant for the statistical analyses.

As described in Section 2.1, data for most of the plants came from multiple sources such as EPA sampling, CWA 308, or plant self

- monitoring

. For three plants (Allen, Belews Creek, and Hatfield’s Ferry), the multiple sources of the data were collected during overlapping time periods, thus, EPA combined these data into a single dataset for the plant

. For two plants (Keystone and Miami Fort), the multiple sources of the data were collected during non

overlap ping time periods

. However, in these instances the time period between the non

overlapping data collection periods was relatively small (two months)

. Furthermore, EPA has no information to indicate that the data represent different operating conditions

. Th us, EPA also combined the multiple sources of data for each of these plants into a single dataset for the plant. This approach is consistent with EPA’s traditional approach for other effluent guidelines rulemakings. Three plants (Brindisi, Polk, and Wabash River) had data from a single source, and for these plants it was not necessary to combine data

. For a listing of all the data and their sampling sources for each of the plants, see DCN SE02002

.



## 3

. Data Corrections, Exclusions, Baseline Substitutions, and Aggregation

This section d escribes the data corrections, exclusions , baseline substitutions, and aggregation s made to the data before developing the effluent limits for each pollutant in each
tech nology option

. It should be note d that even though EPA is not using the arsenic and

mercury data from Allen and Belews Creek to calculate the limits for biological treatment
system ( for the reason described above and in Section 7 ) , EPA did perform data corrections,

### Page 17 

### exclusions, baseline substitutions, and aggregation for the arsenic and mercury data at these two plants.

3.1. Data C orrection s

Several corre ctions were made to the plant self

- monitoring data at Belews Creek due to data entry errors

. In July 2011, EPA’s Engineering and Analysis Division obtained the plant self

monitoring data for Allen and Belews Creek from Duke Energy

. After an initial review of the data, some inconsistencies were found and EPA subsequently asked Duke Energy to addres s the potential errors (an email from Ronald Jordan to Nathan Craig on 07/20/2011 summarized the
apparent inconsistencies). Duke Energy responded to EPA’s request in an email from Nathan Craig to Ronald Jordan (dated 07/21/2011)

. The data issues that were clarified dealt with data
entry errors in certain detection indicators ( see Table 1.1 in Appendix 1)

. Further, after continued interaction between Ron Jordan and Nathan Craig, other data entry errors were also corrected (see Table 1.2 in Appendix 1).

3.2. Data Exclusions and Rationale f or t he Exclus ions

Prior to calculating the effluent limits , EPA thoroughly evaluated the available data
for each plant. EPA identified certain data that warranted exclusion from the limit
calculations because: (i) sampl es were analyzed using an insufficiently

- sensitive analytical method (i.e., use of EPA Method 245.1 instead of Method 1631E for mercury); (ii) the samples were collected during initial commissioning period for the treatment system; or (iii) the analytical results were identified as questionable due to quality control issues, abnormal conditions or treatment upsets, or were analytical anomali es

. Appendix 1 of this document provides a listing of each of the data points that were excluded

.

The sub sections below provide a detailed discussion of the rationale f or each of the
exclusions mentioned above.

3.2.1. Excluding mer cury samples analyzed using an insufficiently

- sensitive analytical m ethod

The plant self

- monitoring data at Allen and Belews Creek were c ollected by Duke Energy to evaluate and optimize the operation of the treatment systems , but note that they are not NPDES compliance monitoring samples. In some cases, Duke Energy analyzed the samples for mercury using EPA Method 1631E, while other samples were analyzed for mercury using EPA
Method 245.1

. Method 245.1 was approved by EPA in 1974 and can ac hieve measurements of mercury down to 200 parts per trillion (ppt), although the Method 245.1 data for both plants
set the detection limit for mercury in the bioreactor samples at 1 part per billion (ppb)

. EPA approved Method 1631E in 2002. This newer meth od has a detection level of 0.5 ppt, making it
400 times more sensitive than Method 245.1.

In a memorandum issued by EPA’s Office of Wastewater Management, EPA directed permitting authorities to ensure that sufficiently

- sensitive analytical methods are u sed when

### Page 18 

### deciding whether to set a permit limitation for mercury and for sampling and analysis of mercury pursuant to the monitoring requirements within a NPDES permit 1



### . One measure for determining whether a method for mercury is “sufficientl y sensitive” is that its method
detection level is low enough relative to the amount of mercury in a plant ’s discharge that t he
method detects the level of mercury present in the discharge

. Since these self

- monitoring samples were not collected for the purpose of demon strating compliance with NPDES permit limits, Duke Energy had the discretion to choose whichever analytical method it wished t o use. However, the detection level for Method 245 .1 is not low enough to detect the concentration of mercury present in the biore actor influent and bioreactor effluent samples, making it inappropriate for use in calculating permit limits

. Similarly, data for samples analyzed with Method 245.1 are inappropriate for use in calculating limits for effluent limitations guidelines
and sta ndards for discharges from power plants

. Therefore, all mercury results that were analyzed using Method 245.1 for bioreactor influent and bioreactor effluent samples were
excluded ( see Appendix 1 for a listing of these exclusions).

3.2.2. Excluding samples collected during the initial commissioning period for the treatment
system

EPA generally excludes data ass ociated with the initial start

- up or commissioning period for a new wastewater treatment system because the data tend to exhibit relatively h igh variability not representative of typical operation

. During the initial commissioning period, the treatment system undergoes a variety of testing to demonstrate that hydraulic flows through the system and equipment such as pumps, valves, and other equi pment operate as designed

. During this period, it is common for changes in process operations to occur as the treatment system undergoes performance verification testing (sometimes referred to as acceptance testing) and the operation is modified to identif y approaches to optimize (i. e., minimize) operational costs or to make adjustments to improve pollutant reductions

. Refinements that may take place during the commissioning period include adjustments to chemical feed locations and/or feed rates; evaluating different pump cycles, filter backwash cycles, clarifier overflow rates, or sludge removal cycles; and changes to the chemicals used

. Generally, this initial period of operation also serves as a time when the operators gain familiarity with the

intricacie s of the treatment system operation

. During this acclimation and optimization period the effluent concentration values may exhibit higher variability than would typically be
observed for a well

- operated treatment system, producing occasional extreme values ( either high or low concentrations)

. After this initial adjustment period, a well

- operated system should operate at steady state (or more precisely, a “quasi

- steady state”) with relatively low variability around a long

- term average

.

Since the plant self

- monitoring data for Allen and Belews Creek Stations included the initial startup and commissioning period for the treatment systems, EPA needed to determine the duration of the commissioning period and to exclude these data points before the analyses

1 James A. Hanlon, Director, Office of Wastewater Management. “Analytical Methods for Mercury in National Pollutant Discharge Elimination System (NPDES) Permits,” August 23, 2007.

### Page 19 

### were performed. The commissioning period for the self

- monitoring data at Allen and Belews
Creek was determined from an engineering perspective based on extensive experience evaluating treatment systems at power plants and other industry sectors and knowledge o f the physical, chemical, and biological treatment processes employed and by looking at the longitudinal plots of all the data

. In addition to the longitudinal plots of individual data, smooth curves (obtained by LOWESS) superimposed on the individual data plots were also examined to help determine when the treatment system appeared to stabilize (see Appendix 2). Th e smoothing technique used (LOWESS) makes minimal assumptions about the distribution of the data and is meant to highlight patterns of the data (see Cleveland (1979, 1981) for more details)

. In examining the longitudinal plots, EPA looked at two types of plots: plots of all the available data and plots of data after the exclusions described in Sections 3.2.1 above and 3.2.3
below

. The conclusion s f rom both of these approaches were consistent

. The initial six months of operation was determined to represent a reasonable estimate of the commissioning period for the treatment systems

. The data associated with the commissioning periods were excluded
fr om the data used to calculate the limits. The data excluded from each of the plants due to the commissioning period are summarized below:

**•** For Allen Station, data from March 3, 2009 through August 26, 2009 were excluded.

**•** For Belews Creek Station, data from February 6, 2008 through July 31, 2008 were
excluded.

3.2.3. Excluding analytical results that were identified as questionable due to quality control (QA/QC ) issues, abnormal conditions or treatment upset, or were analytical anomalies

The bullets below provide a rationale for the exclusions made to the data prior to performing statistical analyses ( see Appendix 1 for a listing of all these exclusions) for the
reasons other than discussed in Sections 3.2.1 and 3.2.2 above

. Note that for a majority of the dates, the FGD purge value was retained in the dataset since these values were not identified as questionable

. The purge values that were retained were used to evaluate the treatment performance

. Thus, in such instances, EPA assumed the FGD purge data accurately reflected the pollutant concentrations in the wastewater transferred to the wastewater treatment system (i.e., treatment system influent) and that the questionable data were associated with the characterization of treatment system performance (i.e., treatment system effluent or intermediate sampling point).

**•** Analytical results that were identified as questionable due to quality control issues: EPA excluded all mercury data collected at Allen and Belews Creek that Duke Energy
identi fied as questionable due to quality control issues

. Duke Energy stated that these data are questionable because they suspected that the matrix spike/matrix spike duplicate (MS/MSD) were not conducted using the FGD wastewater matrix or the MS/MSD indicate d inadequate recoveries

. EPA lacked sufficient laboratory quality control data for these results to make an independent assessment of whether these mercury results should have been retained and included in the statistical analyses.

### Page 20 

### • Abnormal conditions or tr eatment upset : EPA excluded all of the data collected at Allen on dates 3/8/10, 3/22/10, 4/5/10, 4/26/10, 5/10/10, and 5/25/10 for this reason

. When reviewing the data, EPA observed periodic occurrences in early 2010 of unusually high
concentrations of ars enic in the bioreactor effluent relative to effl uent from the
bioreactor influent treatment stage

. According to Duke Energy personnel, the treatment system suffered an upset condition beginning 3/ 2 / 10

, that particularly impacted arsenic

concentrations exit ing the bioreactor

. The treatment system suffered pipe failures in the
bioreactor on 3/ 2/10 and 3/ 11 /10 , dislodging a portion of the carbon within the bioreactor cells. It took approximately four weeks for repairs to be completed, and
additional time for t he treatment system performance to stabilize

. According to Duke Energy, elevated arsenic concentrations in the bioreactor effluent during the period March through May 2010 are likely attributable to the pipe breakages and related repair

activities

. Despite the claim from Duke Energy that only arsenic concentrations were
affected , EPA made the decision to exclude all data collected from date of the first pipe failure until the end of May

.

**•** Abnormal conditions or treatment upset : EPA excluded mercury data collected on 10/5/10 at the chemical precipitation effluent at Hatfield’s Ferry

. This exclusion was due

to an unusually high analytical result inconsistent with proper operation of the BAT/NSPS chemical precipitation treatment technology. Specifically, bas ed on

in formation in the record , the sampling result indicates that the sample may have been contaminated during sample collection or was adversely affected by treatment system upset. The decision to exclude the analytical result (978 ng/L) is supported by the plant’s NPDES compliance monitoring data for that time period. The maximum daily value reported for FGD wastewater treatment system effluent for the month of October 2010

was 127 n g/L. If the excluded value accurately represented the mercury concentra tion in the plant’s FGD treatment system effluent, due to the hydraulic residence times and mixing that occurs in the FGD absorber and the wastewater treatment system, similarly high concentrations of mercury should have been reflected in the plant’s NPDES compliance monitoring samples. Furthermore, the maximum daily values reported by the plant for each monthly reporting period for August 2010 through February 2011 were also substantially lower than the excluded value, ranging from 108 ng/L to 268 ng/L. T he excluded value may be the result of sample contamination occurring during sample collection. EPA used “clean sampling” techniques for its field sampling program, including requiring plant staff to also use such procedures when collecting the CWA 308

sam ples. These clean sampling procedures are intended to minimize the potential fo r contaminating samples, particularly in environments where dust and other contaminants are present. For all plants in the field sampling program

, except Hatfield’s Ferry, the CWA 308 sampling was conducted after EPA had first conducted its on

- site field sampling program. This approach enabled plant staff to become familiar with the specialized sampling collection protocols used for “clean sampling” prior to initiating
thei r CWA 308 sampling. However, in the case of Hatfield’s Ferry, the plant initiated the CWA 308 sampling prior to the EPA field sampling and unfamiliarity with the clean sampling protocols may have allowed the October 2010 sample to become

### Page 21 

### contaminated. If t he excluded result is not associated with sample contamination, then

it indicat es that the plant did not exercise good control of the treatment system during startup following a shutdown period. All three generating units had been shutdown for
at least a w eek preceding the December 2010 sampling event. Unit 3 then started up on October 3, generating electricity at approximately one

- third capacity for the unit. Unit 3 then operated at nearly full load on October 4 and approximately two

- thirds load on
October 5, but then shutdown again on October 6. Based on the information in the record, the FGD wastewater treatment system likely was not operating in a stable manner during this period.

**•** Analytical anomalies : EPA excluded questionable duplicate mercury data collected on 6/9/10 at the bioreactor effluent at Belews Creek

. This exclusion was made since the duplicate value (6

, 440 ng/L ) was drastically different from the split sample value (247 ng/L ) , as well as other results for that sample point

, and so deemed a n analytical anomaly

.

**•** Analytical anomalies : EPA also excluded questionable selenium data collected on 7/14/10 at the bioreactor effluent at Belews Creek

. This exclusion was made since this
observation (299 ug/L) is much higher than any other observed in the remainder of
dataset

. EPA evaluated the selenium contributions in the FGD purge and bioreactor influent (total and dissolved selenium, as well as concentra tions of selenate and selenite), and the values for total selenium, selenite, and selenate in the bioreactor effluent (there are no dissolved selenium results for the bioreactor effluent on that date)

. In addition, EPA evaluated the concentrations for total selenium, dissolved selenium, selenite, and selenate at all three sampling locations for the mo nths preceding and following the July 14 sampling event. Duke Energy personnel reported no
indication of abnormal events or activities at the time of sample collection

. They were unable to explain the result and noted that samples of the ash basin (which r eceives treated FGD wastewater) collected around the same time period did not exhibit a
similar increase in selenium concentrations

. Even taking into account the concentration of selenate present in the FGD purge and bioreactor influent samples, the biorea ctor effluent is substantially higher than would be expected based on the demonstrated performance of the bioreactors at both Allen and Belews Creek Stations

. Furthermore, the Duke Energy self

- monitoring data includes sampling results for other days when
h igh concentrations of selenate were present in the FGD purge and the bioreactor influent, yet the selenium concentrations in the bioreactor effluent were below the proposed effluent limit based on the biological treatment technology option

. Since no plausi ble explanation validating the extreme observation could be determined, EPA excluded the bioreactor effluent selenium observation for July 14, 2010.

3.3. Baseline Substitutions

In general, EPA used detected values or sample

- specific detection limits (for non

detected values) in calculating the effluent limits

. However, there were some instances where
EPA substituted a baseline value for a detected val ue or a sample

- specific detec tion limit

. The

### Page 22 

### baseline value was used in the calculations to account for the possibility that a certain detected result may be at a lower concentration than can be reliably achieved by well

- operated
laboratories

. This approach is consistent with the way EPA has calculated effluent limits in previous effluent guidelines rulemakings

. After excluding all the necessary dat a as described in
Section 3.2 above , EPA compared each reported result to a baseline value

. When a detected value or sample

- specifi c detect ion limit (i.e., sample

- specific quantitation limit) was lower than the baseline value, EPA used the baseline value instead and classified the value as non

- detected (even if the actual reported result was a detected value)

. For example, if the baseline val ue was
5 ug/L and the laboratory reported a detected value of 3 ug/L, EPA’s calculations would treat the sample result as being non

- detected with a sample

- specific detection limit of 5 ug/L.

The table below present s the baseline values that were used for each pollutant for this rulemaking

. It should be noted that in cases when all the concentration values are above the baseline value, then the baseline value has no effect on the concentration values and subsequent li mits. Data for mercury, nitrate

- nitrite as N, and total dissolved solids were all above the baseline values, thus, no baseline substitution was performed. DCN SE02002 provides a listing of all the data, the indicator of whether a baseline substitution wa s performed, and the value after the baseline substitution was performed.

See Section 13 of Technical Development Document for a detailed discussion of the baseline values for each pollutant.

Table 2

. Summary of the baseline va lues used for each pollutant

. Pollutant Baseline Value (unit)

Arsenic 2 ug/L Mercury 0.5 ng/L

Nitrate

- nitrite as N 0.05 mg/L
Selenium 5 ug/L
Total Dissolved Solids 10 mg/L



### In addition to calculating the proposed limits for each pollutant for each technology option adjusting for the baseline values shown above

, EPA calculated what the effluent limits would be using all valid reported results (i.e., without substituting baseline values and/or changing the classification of the result)

. EPA’s purpose in calculating the effluent limits using the data as reported was to allow a comparison between the proposed effluent limits (using baseline values listed above) and the limits that would be obtained without the use of baseline
substitution

. These results are presented in the memo titled “ Assessment of Effluent
Limitations and Standards with No Baseline Substitution for the Steam Electric Rulemaking ”
from Ronald Jordan and Cuc Schroeder (dated November 18 , 2012) to the Steam Electric Rulemaking Record

. This memo is in the record as DCN SE0 2000 (this memo will hereafter be
referred to as DCN SE0 2000 )

.

### Page 23 

### 3.4. Data Aggregation

EPA used daily values in developing the effluent limits

. In cases with two or more samples per day, EPA mathematically aggregated th ese samples to obtain a single value for that day (the procedure to aggregate the samples is described in the subsections below)

. For the samp ling data used in this rulemaking, the re are instances when multiple sample results

are available for a given day

. This occurred with field duplicates, overlaps between plant self

monitoring and EPA sampling, or overlaps between plant self

- mon itoring and CWA 308 sampling.

When aggregating the data, EPA took into account whether each value was detected (D)

or non

- det ected (ND)

. Measurements reported as being less than the sample

- specific detection limit (or baseline values, as appropriate) are designated as non

- detected (ND) for the purpose of statistical analyses to calculate the effluent limits

. In the tables and da ta listings in this document and in the rulemaking record, EPA uses the indicators D and ND denote the censoring type for detected and non

- det ected values, respectively.

The subsections below describe each of the different aggregation procedures. They

are presented in the order that the aggregation was performed; i.e., field duplicates were aggregated first

, and then any overlaps between plant self

- monitoring and EPA sampling data or CWA 308 sampling were aggregated.

3.4.1. Aggregation of field d uplicate s

During the EPA sampling episodes, EPA collected field duplicate samples as part of the quality assurance/quality control activities undertaken to ensure that the quality of the data collected is appropriate for their intended use

. Field duplicates are two samples collected for the same sampling point at approximately the same time

. The duplicates are assigned different sample numbers, and they are flagged as duplicates for a single sampling point at a plant. Because the analytical data from a duplicate pair are intended to characterize the same conditions at a given time at a single sampling point, EPA averaged the data to obtain one value for each duplicate pair.

In most cases, both duplicates in a pair had the same censoring type, so the censoring
typ e of the aggregated value was the same as that of the duplicates

. In some instances, one duplic ate was a detected (D) value but the other duplicate was a non

- detected (ND) value

. When this occurred, EPA determined that the aggregated value should be treate d as detected (D) because the pollutant is confirmed to be present at a level above the sample

- specified detection limit in one of the duplicates

. DCN SE02002 lists the data before the aggregation as well as after the aggregation.

Table 3 below summarizes the procedure for aggregating the sample measurements from the field duplicates

.

### Page 24 

### Table 3

. Aggregation of Field Duplicates

. If the field duplicates are: Censoring type of average is: Value of the aggregate is: Formulas for aggregate values of duplicates
Both detected D Arithmetic average of measured values (D 1 

### + D 2 

### )/2

Both non

- detected ND Arithmetic average of sample

- specific detected limits (or baseline) (DL 1 

### + DL 2 

### )/2

One detected and

one non

- detected D Arithmetic average of measured value and sample

- specific detection limit (or baseline) (D + DL)/2

D: detected.

ND: non

- detected. DL: sample

- specific detection limit.



### 3.4.2. Aggregation of overlapping s amples

At the Allen and Belews Creek plants, sampling data were available from EPA sampling, CWA 308 sampling, and plant self

- monitoring

. As explained in Section 2.3 above, there was some overlap between the data from these sources

. On some days at a given plant, samples were available from two sources, specifically, plant self

- monitoring and either EPA sampling or CWA 308 sampling

. When these overlaps occurred, EPA aggregated the measurements from the available samples to obtain one value for that day. DCN SE02002 lists the data before the aggregation as well as after the aggregations.

The procedure averaged the measurements to obtain a single value for that day

. When both measurements had the same censoring type, then the censoring type of the aggregate was the same as that of the overlapping values

. Wh en one or more measurements were detected (D), EPA determined that the appropriate censoring type of the aggregate was detected because the pollutant is confirmed to be present at a level above the sample

- specific detection limit in one of the samples

. The procedure for obtaining the aggregated value and censoring type is similar to the procedure shown in Table 3 above

.



## 4 . Data Editing Criteria

After excluding and aggregating the data, EPA applied data editing criteria on a pollutant

- by

- pollutant basis t o select the datasets to be used for developing the effluent limits for each technology option

. These criteria are referred to as the long

- term average test (or LTA test)

. EPA established the LTA test to ensure that the pollutants for which limits are being proposed were present in the influent at sufficient concentrations to evaluate treatment effectiveness at the plant

. The influent first had to pass a basic requirement that 50% of the influent measurements for the pollutants had to be detected at any concentration

. If the dataset at a plant passed the basic requirement, then the data had to pass one of the following two criteria to pass the LTA test:

### Page 25 

### Criterion 1. At least 50% of the influent measurements in a dataset at a plant were detected at levels equal to or greater than 10 times the baseline value ( shown in

Section 3.3 ).

Criterion 2. At least 50% of the influent measurements in a dataset at a plant were
de tected at any concentration and the influent arithmetic average was equal to or greater than 10 times the baseline value ( shown in Section 3.3 ).

If the dataset at a plant failed the basic requirement, then EPA automatically set both
Criteria 1 and 2 to “f ail”

. If the dataset for a plant failed the basic requirement, or passed the basic requirement but failed both criteria, EPA would exclude the plant’s effluent data for that pollutant when calculating limit s

. Through the application of the LTA test, EPA en sures that the
limits result from treatment of the wastewater and not simply the absence or substantial
dilution of that pollutant in the waste stream.

After performing the LTA test for all the pollutants at each plant that was selected as the
basis for the limits for this rulemaking, it was found that all the datasets passed the LTA test except for arsenic and mercury data at Wabash River

. Thus, data for arsenic and mercury at
Wabash River were excluded from the calculation of the limits

. See Appendix 3 for the results of the LTA test for each pollutant at each plant.



## 5. Statistical Methodology

The sections below provide the following: (i) general defi nitions and background , (ii)
statistical m odel s elected for the data, (iii) analys i s of autocorrelation , (iv) data set requirement, (v) the calculation of the effluent limits, and (vi) description of how the limit was set in a special
case where most of t he observations were non

- detects

.

5 .1. Definitions and Background

In developing the effluent limits , a statistical procedure is used that involves fitting
efflu ent data to a distribution and estimating specified upper percentil es of the fitted
distribution

. The bullets below describe in detail the important quantities that are typically
estimated based on the effluent data.

**•** The long

- term average (LTA) is the average concentration that is achieved over a period
of time

. The long

- term average is the mean of the underlying statistical distribution of the daily effluent values.

**•** The daily maximum limitation is the highest allowable discharge in any one day

. The daily maximum limitation is the estimate of the 99 th 

### percentile ( denoted as P 99 

### ) of the distribution of the daily effluent values.

### Page 26 

### • The daily variability factor is the ratio of the daily maximum limitation to the LTA

. This ratio represents the relationship between the large values and the average treatment performance level that a well

- design ed and well

- operated treatment system should be capable of achieving at all times.

**•** The monthly average limitation is the highest allowable average of discharges calculated from the effluent data collected over a calendar month (or period of time specified in the permit)

. The monthly average limitation is the estimate of the 95 th 

### percentile ( denoted as P 95 

### ) of the distribution of the monthly averages of the daily effluent values.

**•** The monthly variability factor is the ratio of the monthly average limitatio n to the LTA.

5 .2. Statistical Model Selected for the Data

In calculating the long

- term average, variability factors, and effluent limits, a statistical
model is assumed for the distribution of the effluent data

. For this rulemaking, EPA selected
the mo dified delta

- lognormal distribution to model pollutant effluent concentration to develop the long

- term average, variability factors, and limits

. A typical effluent dataset from EPA sampling, CWA 308 sampling, or from a plant’s self

- monitoring con sists of a mixture of detected
and non

- detected values. The modified delta

- lognormal distribution is appropriate for such
datasets because it models the data as a mixture of detected measurements that follow a lognormal distribution and non

- detect measurem ents that occur with a certain probability. The model also allows for the possibility that non

- detected measurements occur at multiple sample

- specific detection limits. Because the data appeared to fit the modified delta

- lognormal model reasonably well, EP A has determined that this model is appropriate for these data

. See Appendix B of the Technical Development Document for an overview of the statistical model and a description of the procedures EPA used to estimate the se parameters.

5 .3. Autocorrelation Analysis

Effluent concentrations that are collected over time may be autocorrelated. The data are positively autocorrelated when measurements taken at specific time intervals, such as one or two days apart, are similar. For example, positive autocorrelati on would occur if the effluent

concentration was relatively high one day and was likely to remain high on the next and possibly succeeding days. Because the autocorrelated data affect the true variability of treatment performance, EPA typically adjusts the variance estimates for the autocorrelated data, when appropriate

.

For this rulemaking, whenever there was sufficient data for a pollutant at a plant to evaluate the autocorrelation reliably, EPA estimated the autocorrelation and incorporated it
into the calculation of the limits . For a plant without enough data to reliably evaluate and obtain a reliable estimate of the autocorrelation, EPA set the autocorrelation to zer o in the
calculation of the effluent limits. EPA did so because it is reasonable to se t the autocorrelation to zero whenever there is not a sufficient amount of data to reliably evaluate the
autocorrelation and when there is no correlation available that can be transferred from a

### Page 27 

### similar technology and waste stream

. See the memorandum title d “ Serial correlations for Steam Electric with and without adjustment for baseline values [EP

- C

- 10

- 023 WA 2

- 6 (Steam Electric)] ” from John Rogers to Cuc Schroeder

, dated April 15 , 2013

, for details of the statis tical methods and procedures used to determine the autocorrelation values, as well as a detailed
discussion of the minimum number of observations needed to obtain a reliable estimate of the
autocorrelation . T his memo is in the record as DCN SE02001 (this memo will hereafter be
refer red to as DCN SE02001 ) . The following paragraphs describe the instances where EPA was able to obtain an estimated autocorrelation and the assumptions made about the
autocorrelation when there were too few observations to estimate the autocorrelation.

For the biological treatment technology for FGD wastewater (represented by Allen and Belews Creek plants), EPA was able to perform a statistical evaluation of the autocorrelation and obtain a reliable estimate of the autocorrelation because several years of da ta were available for these plants

. For arsenic and mercury, EPA is proposing to transfer the limits from the chemical precipitation technology option for FGD for these pollutants (see Section 13 of the

T echnical Development Document for a detailed discussion of the transfer of the limits). The Allen and Belews Creek plants do not include sulfide precipitation in the upstream chemical precipitation system to achieve the BAT level of control for arsenic and mercury , thus, the

arsenic a nd mercury data from these plants were not appropriate for use in estimating

autoco rrelation. However, if EPA was to use these data to estimate autocorrelation for arsenic and mercury, it would follow the methodology used to estimate autocorrelation for s elenium.
Table 4 below lists the autocorrelation values used in the limits calculation for nitrate

- nitrite as
N and selenium.

Table 4

. Summary of Estimated Autocorrelation Values at Allen and Belews Creek

.

Pollutant Correlation va lue used for limit calculations
Selenium 0.291 Nitrate

- nitrite as N 1

1 : There were only eight obs ervations available for nitrate

- nitrite as N (only EPA sampling and CWA 308 sampling data available) at Allen and Belews Creek, so EPA was not able t o evaluate the autocorrelation

. However, EPA transferred the autocorrelation from selenium since these two chemicals behave similarly in the biological
treatment system.



### For the chemical precipitation treatment option for FGD wastewater (represented by

Hat field’s Ferry, Keystone, and Miami Fort plants), for the vapor

- compression evaporation treatment technology option for FGD wastewater (represented by Brindisi), and for the vapor

compression treatment technology option for gasification wastewater (represen ted by Polk and Wabash River), EPA was unable to perform an evaluation and obtain a reliable estimate of the autocorrelation because there were too few observations available at the plants. Thus, for these plants, EPA set the autocorrelation to zero in the calculatio n of the limit s. EPA did so
because there were not sufficient data to reliably evaluate the autocorrelation, nor did EPA
have a valid correlation estimate available that could be transferred from a similar technology
and waste stream

.

### Page 28 

### 5 .4. Data s et Requirement

The statistical model require s at least two distinct detected values in order to estimate the variance of the distribution (i.e., to allow the variability factor to be calculated)

. Generally, EPA has been reluctant to estimate a variability factor from plants with a small numbe r of
detected observations

. The minimum number of observations required to calculate the variability factor has been evaluated on a case

- by

- case basis

. For example, for the Organic Chemicals, Plastics and Synthetic Fib ers (OCPSF) rulemaking, a variability factor was estimated for a plant if it had at least 7 daily observations with at least 3 observations above the detection
limit

. In the Iron and Steel rulemaking, a variability factor was estimated for a plant if it ha d at least three observations, at least two of which were abov e the detection limit

. For the steam electric rulemaking, a variability factor was estimated for a plant if it had at least three observations, at least two of which were above the detection li m it

.

5 .5. Calculating Effluent Limits for Each Pollutant in Each Technology Option

EPA calculated the percentiles that are used as a basis for the limits by multiplying the long

- term average (the option long

- term average discussed below) by the appropriate variability factors (the option variability factor discussed below)

. The p aragraphs below describe the calculation of the option long

- term average, option variability factors, and effluent
limits

. As mentioned in Section 1, the option long

- te rm averages and variability factors in this document refer to the long

- term average and variability factors for that particular technology option, not the regulatory option described in Section 8 of the Technical Development

Document.

The option long

- term average is calculated for a pollutant using two steps

. First, EPA calculated the plant

- specific long

- term average for each pollutant that had enough distinct detected values by fitting a statistical model to the daily concentration values

. In cas es when a dataset for a specific pollutant did not ha ve enough distinct detected values, then the statistical model was not used to obtain the long

- term average

. In these cases, the plant

- specific long

term average for each pollutant was the arithmetic mea n of the availabl e daily concentration
values

. Second, the option long

- term average for each pollutant is calculated as the median of the plant

- specific long

- term averages for that pollutant.

The following describes the calculations performed to obtain th e option variability factors. First, EPA calculated the plant

- specific variability factors for each pollutant that had enough distinct detected values by fitting a statistical model to the daily concentration values

. Each plant

- specific daily variability f actor for each pollutant is the estimated 99 th 

### percentile of the distribution of the daily concentration values divided by the plant

- specific long

- term

average

. Each plant

- specific monthly variability factor for each pollutant is the estimated 95 th



### percent ile of the distribution of the 4

- day average concentration divided by the plant

- specific long

- term average. The calculation of the plant

- specific monthly variability factor assumes that the monthly averages are based on the pollutant being monitored weekly (approximately four times each month)

. In cases when there were not enough distinct detected values for a specific

### Page 29 

### pollutant, then the statistical model was not used to obtain the variability factors

. In these cases, the data for the pollutant at the plan t was excluded from the calculation of the option variability factors.

Finally, the daily maximum limit for each pollutan t for each technology option is the product of the option long

- term average and option daily variability factors

. The monthly

average limit for each pollutan t for each technology option is the product of the option long

term average and optio n monthly variability factors.

5.6 . Special Case

– Effluent Lim it s Based on Detection Limits

Although the percentile estimates described in the secti on above play an important role in determining daily maximum and monthly average effluent limits, they are not a requirement under the Clean Water Act and are not always used as the basis for effluent limits

. In situations
where there are too few dete cted results, the statistical models are not appropriate for use in obtaining the effluent limits since reliable estimates could not be calculated from the model

. In such instances, EPA has instead established the daily effluent limits based on a detection limit

. Also , the monthly average limit is not established when the daily limit is based on the detection
limit

. The purpose of a monthly average limit is to require dischargers to provide better control, on a monthly basis, than required by the daily maxi mum limit

. However, for these pollutants, current analytical methods cannot measure below the detection limit specified for the daily
maximum limit

. Thus, even if a permitting or pretreatment authority requires more frequent monitoring for these pollutants than once a month, monthly average limits would still be expressed as less than detection limits.



## 6. Treatment Technology Option for FGD Wastewater: Chemical Precipitation

EPA used data from three coal

- fired power plants ( Hatfield’s Ferry, Keysto ne, and Miami Fort) to develop the long

- term averages, variability factors, and effluent limit s for the chemical precip itation treatment technology option for FGD wastewater

. The pollutant s for which the
limits are calculated are arsenic and mercury

.

The following provide s a detailed summary of all th e available data for each plant. The available data from each of the plants came from the following two sources: EPA sampling and

CWA 308 sampling. As explained in Section 2.3, EPA combined these two sources o f data at each plant into a single dataset for the plant. The data described below include all the available data prior to any of the exclusions

.

Hatfield’s Ferry Sampling Data

The sampling data were collected at two sampling locations: FGD Purge and ch emical precipitation effluent

. The bullets below provide a brief summary of the data:

### Page 30 

### • EPA sampling data collected by EPA between 12/06/2010 and 12/10/2010.

**•** CWA 308 sampling data collected by the plant one day per month for four consecutive
months

. These d ata were collected on 10/5/2010, 11/10/2010, 1/12/2011, and 02/09/2011.

Keystone Sampling Data

The sampling data were collected at two sampling locations: FGD Purge and chemical precipitation effluent

. The bullets below provide a brief summary of the dat a:

**•** E PA sampling data collected by EPA between 09/13 /2010 and 09/17/2010.

**•** CWA 308 sampling data collected by the plant one day per month for four consecutive
months

. These data were collected on 10/7/2010, 11/4/2010, 12/9/2010, and 01/13/2011.

Miami Fort Sampling Data

The sampling data were collected at two sampling locations: FGD Purge and chem ical precipitation effluent

. The bullets below provide a brief summary of the data for each of the
data sources:

**•** EPA sampling data collected by EPA between 07/ 12 /2010 and 07/16/2010.

**•** CWA 308 sampling data collected by the plant one day per month for four consecutive
months

. These data were collected on 09/28/2010, 11/2/2010, 12/7/2010, and 01/14/2011.

EPA attempted to use the available data to estimate the autoc orrelation

. However, for
Hatfield ’s Ferry, Keystone, and Miami Fort, EPA was not able to perform an evaluation of the
autocorrelation because there were too few observa tions available at the plants

. Thus, for these plants, EPA set the autocorrelation to zero in the development of the limits for the
reasons described in section 5.3

.

The sections below provide the following for each of the pollutants at each of the plants: longitudinal plots of the data, summary statistics, and plant

- specific long

- term av erage and plant

- specific variability factors (see Appendix B for an overview of the statistical model and the procedures used to estimate the plant

- specific long term average and variability factors)

. Also provided in the sections below are the option long

- term average, option variability factors, and effluent limits for each pollutant. All exclusions, baseline substitutions, and aggregation of data were made prior to conducting the analyses presente d below

.

### Page 31 

### 6 .1. Chemical Precipitation Treatment for FGD Wastewater: A rsenic

6.1.1. Longitudinal plots of the data for arsenic (ug/L)

Below are the longitudinal plots of the arsenic concentrations (on a logarithmic scale)
for Hatfield’s Ferry , Keystone, and Miami Fort

. In the plot s below, the plot on the left shows the
concentrations for Hatfield’s Ferry , the plot in the middle shows the concentrations for Keystone, and plot on the right shows the concentrations for Miami Fort

.

Figure 1 . Plot of arsenic (ug/L) data on a logarithmic scale for Hatfield’s Ferry, Keystone, and

Miami Fort.

6.1.2. Summary statistics for arsenic (ug/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sampl e

- specific detection limits by sample location and plant

. For example, for Hatfield’s Ferry at the FGD Purge sampling location , all 8 observations were detected; at the chemical precipitation effluent sampling location, of the 8 observations, 6 observation s were detected and 2 were non

- detected

. Of the 2 non

- detects, both had a detection limit of 4 ug/L (shown at the top of the column).5102050100200500100020005000 Hatfields Ferry (logarithmic scale)

Date Note: Detected = o Non-Detected = *Arsenic (ug/L)

Oct 10 Nov 10 Dec 10 Jan 11 Feb 11 * * FGD Purge Chem Prep. Eff.5102050100200500100020005000 Keystone (logarithmic scale)

Date Note: Detected = o Non-Detected = *Arsenic (ug/L)

Sep 10 Oct 10 Nov 10 Dec 10 Jan 11 * * * * * * * FGD Purge Chem Prep. Eff.5102050100200500100020005000 Miami Fort (logarithmic scale)

Date Note: Detected = o Non-Detected = *Arsenic (ug/L)

Jul 10 Sep 10 Nov 10 Dec 10 Jan 11 * * FGD Purge Chem Prep. Eff.

### Page 32 

### Table 5

. Numbers of detected and non

- detected observations and sample

- specific detection
limits for arsenic (ug/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 2 ) Indicator (n) 3 Sample Specific Detection Limits for Arsenic (ug/L)

Detection Limit = 4

Hatfield’s Ferry 1 FGD Purge (N = 8) D (n=8)

Chemical Prep. Effluent (N = 8) D (n=6)

ND (n=2) 2

Keystone 1 FGD Purge (N = 8) D (n=8)

Chemical Prep. Effluent (N = 8) D (n=1)

ND (n=7) 7

Miami Fort 1 FGD Purge (N = 8) D (n=8)

Chemical Prep. Effluent (N = 8) D (n=6)

ND (n=2) 2

1 : Combination of EPA sampling and CWA 308 sampling.

2 : Detected and non

- detected observations combined.

3 : D = detected and ND = non

- detected.



### The table below provides the summary statistics for all observations (detected and non

detected combined) for eac h sampling location at each of the plants

.

Table 6 . Summary statistics of arsenic concentration (ug/L) for all detected and non

- detected samples combined, by plant and sampling location.

Plant Name Sampling Location Summary Statistics for Arsenic (ug/L)

N 2 Minimum Mean Median Maximum Std

Hatfield’s Ferry 1 FGD Purge 8 300.0 1,796.3 1,575.0 4,610.0 1,471.2
Chemical Prep. Effluent 8 4.0 6.6 5.9 11.0 2.7

Keystone 1 FGD Purge 8 450.0 1,815.0 2,035.0 3,080.0 1,021.6
Chemical Prep. Effluent 8 4.0 4.0 4.0 4.1 0.0 2

Miami Fort 1 FGD Purge 8 320.0 727.3 682.5 1,310.0 315.9
Chemical Prep. Effluent 8 4.0 4.5 4.4 5.0 0.4

1 : Combination of EPA sampling (4 daily samples) and CWA 308 sampling (4 monthly samples).

2 : Detected and non

- detected observations combined.



### 6.1.3. Plant

- specific long

- term average s and variability factors, option long

- term average and

v ariability factors, and effluent limits for arsenic (ug/L)

The table below provides the plant

- specific LTA, plant

- specific variability factors, option LTA, option variability factors, and effluent limits for arsenic at the chemical precipitation
effluent

.

### Page 33 

### Table 7

. Plant

- specific long

- term averages and variability factors, option long

- term average and variability factor s, and limits for arsenic (ug/L) at chemical precipitation effluent.

TYPE Plant Name N 2 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

Specific Hatfield’s Ferry 1 8 (D = 6, ND = 2) 6.682 2.285 1.373 Keystone 1 8 (D = 1,ND = 7) 4.006 3

-- 4

-- 4

Miami Fort 1 8 (D = 6,ND = 2) 4.483 1.197 1.072 Option 4.483 1.741 1.223 7.805 5.480

1 : Combination o f EPA sampling and CWA 308 sampling

. 2 : D = detected and ND = non

- detected.

3 : Long

- term average is the arithmetic mean since there were too few detected observations (not able to estimate the variance of the distribution).

4 : Nearly all observations were non

- detected, so the variability factors could not be calculated.



### 6 .2. Chemical Precipitation Treatment for FGD Wastewater : Mercury

6.2.1. Longitudinal plots of the data for mercury (ng/L)

Below are the l ongitudinal plots of the mercury concentrations (on a logarithmic scale)
for Hatfield’s Ferry , Keystone, and Miami Fort.

Figure 2 . Plot of mercury (ng/L) data on a logarithmic scale for Hatfield’s Ferry, Keystone, and

Miami Fort.

6.2.2. Summary statistics for mercury (ng/L)

All observations at each of the sampling locations for Hatfield’s Ferry , Keystone, and
Miami Fort were detected

. The table below provides summary statistics for all observations for each sampling location at each of the plants.1e+021e+031e+041e+051e+06 Hatfields Ferry (logarithmic scale)

Date Note: Detected = o Non-Detected = *Mercury (ng/L)

Oct 10 Nov 10 Dec 10 Jan 11 Feb 11 FGD Purge Chem Prep. Eff.1e+021e+031e+041e+051e+06 Keystone (logarithmic scale)

Date Note: Detected = o Non-Detected = *Mercury (ng/L)

Sep 10 Oct 10 Nov 10 Dec 10 Jan 11 FGD Purge Chem Prep. Eff.1e+021e+031e+041e+051e+06 Miami Fort (logarithmic scale)

Date Note: Detected = o Non-Detected = *Mercury (ng/L)

Jul 10 Sep 10 Nov 10 Dec 10 Jan 11 FGD Purge Chem Prep. Eff.

### Page 34 

### Table 8

. Summary statistics of mercury concentration (ng/L) for all detected samples by plant and sampling location.

Plant Name Sampling Location Summary Statistics for Mercury (ng/L)

N 2 Minimum Mean Median Maximum Std

Hatfield’s Ferry 1 FGD Purge 8 184,000.0 465,125.0 467,000.0 789,000.0 216,886.7
Chemical Prep

. Effluent 7 31.8 75.8 38.4 228.0 70.4

Keystone 1 FGD Purge 8 18,800.0 404,225.0 514,000.0 622,000.0 213,272.3
Chemical Prep

. Effluent 8 26.4 62.8 52.6 119.0 35.9

Miami Fort 1 FGD Purge 8 44,000.0 235,375.0 227,500.0 384,000.0 116,880.8
Chemical Prep

. Effluent 8 101.0 167.6 146.0 295.0 70.7

1 : Combination of EPA sampling and CWA 308 sampling

. 2 : Detected and non

- detected observations combined (all observations were detected).



### 6.2.3. Plant

- specific Long

- term average s and variability factors, option long

- term average and variability factors, and effluent limits for mercury (ng/L)

The table below provides the plant

- specific LTA, plant

- specific variability factors, option

LTA , option variability factors, and effluent limits for mercury at chemical precipitation effluent

.

Table 9

. Plant

- specific long

- term average and variability fac tors, option long

- term average and

va riability factors, and limits for mercury (ng/L) at chemical precipitation effluent.

Type Plant Name N 2 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

specific Hatfield’s Ferry 1 7 (D = 7, ND = 0) 75.404 4.083 1.766 Keystone 1 8 (D = 8, ND = 0) 64.260 3.257 1.584

Miami Fort 1 8 (D = 8, ND = 0) 168.569 2.286 1.361 Option 75.404 3.209 1.570 241.948 118.396

1 : Combination of EPA sampling and CWA 308 sampling

. 2 : D = detected and ND = non

- detected.



### 6.3

. Chemical Precipitation Treatment for FGD Wastewater : Summary of the Option Long

- Term Averages
, Option Variabil ity Factors, and Effluent Limits

The table below provides a summ ary of the option long

- term average s , option variability factors, and effluent limits for a rsenic and mercury

.

Table 10

. Summary of option long

- term averages, option variability factors, and effluent limits for chemical precipitation FGD wastewater treatment technology.

Pollutant Autocorrelation
Value Option

LTA Option Daily Variability Factor Option Monthly Variability

Fact or Daily
Limit 1 Monthly Average

Limit 1

Arsenic (ug/L) 0 4.483 1.741 1.223 8 6 Mercury (ng/L) 0 75.404 3.209 1.570 242 119

1 : Effluent limitations greater than 1.0 have been rounded upward to the next highest integer.

### Page 35 

## 7. Treatment Technology Option for FGD Wastewater: Biological Treatment

EPA used data from two coal

- fired power plants (Allen and Bel ews Creek) to develop the long

- term averages, variability factors, and effluent limit s based on the chemical precipitation followed by biological treatment technology option for FGD wastewater

. Summary statistics for arsenic, mercury, nitrate

- nitrite a s N

, and selenium are presented for these two plants

. The data from these two plants were used to calculate the limits for nitrate

- nitrit e as N and
selenium. As noted above, while these two plants operate the biological treatment system used as the basis for the technology option, neither of these plants includes sulfide precipitation in the upstream chemical precipitation system

. For this reason, EPA is proposing to transfer the arsenic and mercury limits calculated based on the chemical precipitation technology option to biological technology option for FGD wastewater (see Section 13 of the Technical Development
Document for a detailed dis cussion of the transfer of limits)

.

The following provides a detailed summary of all the available data for each plant

. The
available data from each plant came from the follo wing three sources: (i) plant self

- monitoring, (ii) EPA sampling , and (iii) CWA 308 sampling

. As explained in Section 2.3, EPA combined the multiple sources of data at each plant into a single dataset for the plant. The data described
below includes all the available data prior to any of the exclusions

.

Allen Sampling Data

The sam pling data were collected at three sampling locations: FGD purge, bioreactor
influent , and bioreactor effluent

. The bullets below prov ide a brief summary of the data :

**•** Plant self

- monitoring data collected by the plant over a period of several years

. The

or iginal data provided were collected betw een 03/03/2009 and 05/23/2011.

**•** EPA sampling data collected by EPA between 08/02/2010 and 08/06/2010.

**•** CWA 308 sampling data collected by the plant one day per month for four consecutive
months

. These data were collect ed on 10/5/2010, 11/1/2 010, 12/6/2010, and 01/12/2011.

Belews Creek Sampling Data

The sampling data were collected at three sampling locations: FGD purge, bioreactor
influent , and bioreactor effluent

. The bullets below prov ide a brief summary of the data :

**•** Plant self

- monitoring data collected by the plant over a period of several years

. The original data provided were from 02/06/2008 to 05/25/2011.

**•** EPA sampling data collected by EPA between 06/07/2010 and 0 6/11/20110.

**•** CWA 308 sampling data collected by the plant one day per month for four consecutive
months

. These data were collected on 10/6/2010, 11/3/2 010, 12/8/2010, and 01/18/2011.

### Page 36 

### EPA was able to estimate the autocorrelations for use in the calculation of the limits at
All en and Belews Creek (at the bioreactor effluent sampling location) because several years of data were available for these plants

. See DCN SE2001 for the statistical method and results of the autocorrelation values for each pollutant

. Thus, the estimated au tocorrelation values were used in developing limits for each pollutant for this technology option

. However, an
autocorrelation value of zero (0) was also used to assess the sensitivity of the limits to the
correlation values used

. The effluent limits calcu lated using both approaches are presented
below

. The proposed limits for this technology option are based on the calculation s that incorporated the estimated autocorrelations.

The s ections below provide the following for each of the pollutant s at each of the plants: longitudinal plots of th e data and summary statistics

. Also provided in the sections
below are the plant

- specific and option long

- term average s , plant

- specific and option v ariability factors, and effluent limits for nitrate

- nitrite a s N and se lenium

. All exclusions, baseline substitutions, and aggregation of data were made prior to conducting the analyses described
below

.

7 .1. Biological Treatment for FGD Wastewater : Arsenic

Sections below provide the longitudinal plots and summary statisti cs for arsenic. EPA did
not calculate the limits for arsenic using the Allen and Belews Cree k because EPA is transferring the arsenic limits calculated based on the chemical precipitation technology option to the biological technology option for FGD wastew ater (see Section 13 of the Technical Development Document for a detailed discussion of the transfer of limits). If EPA was to use these data to calculate limits for arsenic, it would follow the same methodology used to calculate the limits
for nitrate

- ni trite as N and selenium for this technology option

.

7.1.1. Longitudinal plots of the data for arsenic (ug/L)

Below are the longitudinal plots of the arsenic concentrations (on a logarithmic scale)
for Allen and Belews Creek

. In the plot below, the plot on the left shows the concentrations for Allen from 09/09/2009 to 05/23/2011, while the plot on the right shows the concentrations for Belews Creek from 08/01/2008 to 05/25/2011

. Note that the data collected in the first six months for each plant was exclu ded because it represented the initial commissioning period for the treatment system.

### Page 37 

### Figure 3 . Plot of arsenic (ug/L) data on a logarithmic scale for Allen and Belews Creek.

7.1.2. Summary statistics for arsenic (ug/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location and plant.

Table 11

. Numbers of detected and non

- detected observations and sample

- specific detection limits for arsenic (ug/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 2 ) Indicator (n) 3 Sample Specific Detection Limits for Arsenic (ug/L )

2 3 4 4.5 5 7 10 14.5 52

Allen 1 FGD Purge (N = 63) D (n = 63)

Bioreactor Influent (N = 63) D (n = 1)

ND (n = 62) 1 5 16 3 37

Bioreactor Effluent (N = 62) D (n = 27)

ND (n = 35) 5 26 4

Belews Creek 1 FGD Purge (N = 70) D (n = 70)

Bioreactor Influent (N = 71) D (n = 9)

ND (n = 62) 5 1 18 1 36 1

Bioreactor Effluent (N = 71) D (n = 4)

ND (n = 67) 17 1 6 1 12 29 1

1 : Combination o f EPA sampling , CWA 308 sampling, and plant self

- monitoring

. 2 : Detected and non

- detected observations combined.

3 : D = detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for arsenic concentrations by sampling location and plant

.251020502005002000 Allen (logarithmic scale)

Date Note: Detected = o Non-Detected = *Arsenic (ug/L)

Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11

* * * *

* *

* * * * * * * * * * * * * *

* *

* * * * * * * * * * * *

* * * * * * * * * *

* * * * *

* * * *

* * * * * * * * * * * FGD Purge Bioreactor Inf. Bioreactor Eff.251020502005002000 Belews Creek (logarithmic scale)

Date Detected: o Non-Detected: *Arsenic (ug/L)

Aug 08 Jan 09 Jun 09 Nov 09 Apr 10 Sep 10 Feb 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * *

* * * * * * * * *

* *

* *

* * * * * *

*

* * * *

* *

* * * * * * * * * *

* * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * *

* * * * * *

* * *

* * *

* * *

* *

* *

* * * * * * * FGD Purge Bioreactor Inf. Bioreactor Eff.

### Page 38 

### Table 12 . Summary statistics of arsenic concentration (ug/L) for all detected and non

- detected samples combined, by plant and sampling location.

Plant Name Sampling Location Summary Statistics for Arsenic (ug/L)

N 2 Minimum Mean Median Maximum Std

Allen 1 FGD Purge 63 105.0 233.3 208.0 619.0 112.9

Bioreactor Influent 63 2.0 7.9 10.0 10.0 2.7

Bioreactor Effluent 62 2.0 5.9 5.0 20.1 3.1

Belews Creek 1 FGD Purge 70 92.0 411.4 278.0 2,820.0 377.0

Bioreactor Influent 71 4.0 8.9 10.0 52.0 5.9

Bioreactor Effluent 71 2.0 6.2 5.0 14.5 3.6

1 : Combination o f EPA sampling , CWA 308 sampling , and plant self

- monitoring

. 2 : Detected and non

- detected observations combined.



### 7.2

. Biological Treatment for FGD Wastewater: Mercury

Sections below provide the longitudinal plots and summary statistics for mercury . EPA
did not c alculate the limits for mercury using the Allen and Belews Cree k because EPA is transferring the mercury limits calculated based on the chemical precipitation technology option to the biological technology option for FGD wastewater (see Section 13 of the T echnical Development Document for a detailed discussion of the transfer of limits). If EPA was to use
these data to calculate limi ts for arsenic, it would follow the same methodology used to
calculate the limits for nitrate

- nitrite as N and selenium for t his technology option

.

7.2.1. Longitudinal plots of the data for mercury (ng/L)

Below are the longitudinal plots of the mercury concentrations (on a logarithmic scale)
for Allen and Belews Creek.

Figure 4 . Plot of mercury (ng/L ) data on a logarithmic scale for Allen and Belews Creek.1e+011e+031e+05 Allen (logarithmic scale)

Date Note: Detected = o Non-Detected = *Mercury (ng/L)

Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 FGD Purge Bioreactor Inf. Bioreactor Eff.1e+011e+031e+05 Belews Creek (logarithmic scale)

Date Detected: o Non-Detected: *Mercury (ng/L)

Aug 08 Jan 09 Jun 09 Nov 09 Apr 10 Sep 10 Feb 11 FGD Purge Bioreactor Inf. Bioreactor Eff.

### Page 39 

### 7.2.2. Summary statistics for mercury (ng/L)

All observations at each of the sampling locations for Allen and Belews Creek were
detected

. The table below prov ides summary statistics for all observations for mercury concentrations by sampling location and plant.

Table 13 . Summary statistics of mercury concentration (ng/L) for all detected and non

- detected samples combined by plant and sampling location.

Plant Name Sampling Location Summary Statistics for Mercury (ng/L)

N 2 Minimum Mean Median Maximum Std

Allen 1 FGD Purge 62 18,500.0 52,219.4 49,950.0 120,000.0 22,934.2

Bioreactor Influent 38 22.7 358.8 242.5 1,320.0 382.2

Bioreactor Effluent 39 1.9 13.0 9.9 54.6 12.2

Belews Creek

1 FGD Purge 73 1,000.0 194,417.8 185,000.0 697,000.0 120,110.3

Bioreactor Influent 40 6.8 7,647.9 112.5 53,300.0 17,768.8

Bioreactor Effluent 38 2.0 111.6 11.5 746.0 177.6

1 : Combination o f EPA sampling , CWA 308 sampling, and plant self

- monitoring data.

2 : Detected and non

- detected observations combined (all observations were detected)

.



### 7 .3. Biological Treatment for FGD Wastewater: Nitrate

- n itrite as N

7.3.1. Longitudinal plots of the data for nitrate

- nitrite as N (mg/L)

Below are the l ongitudinal plots of the nitrate

- nitrite as N concentrations (on a logarithmic scale) for Allen and Belews Creek.

Figure 5

. Plot of nitrate

- nitrite as N (m g/L) data on a logarithmic scale for Allen and Belews Creek (for short, the name on the vertical is labeled as nitrite)

.0.10.20.51.02.05.010.050.0 Allen (logarithmic scale)

Date Note: Detected = o Non-Detected = *Nitrite (mg/L)

Aug 10 Oct 10 Nov 10 Dec 10 Jan 11 * * * * * * * FGD Purge Bioreactor Inf. Bioreactor Eff.0.10.20.51.02.05.010.050.0 Belews Creek (logarithmic scale)

Date Detected: o Non-Detected: *Nitrite (mg/L)

Jun 10 Oct 10 Dec 10 Jan 11 * * * * FGD Purge Bioreactor Inf. Bioreactor Eff.

### Page 40 

### 7.3.2. Summary statistics for nitrate

- nitrite as N (mg/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the s ample

- specific detection limits by sample location and plant.

Table 14 . Number of detected, non

- detected, and sample

- specific detection limits for

nitrate

- nitrate as N (mg/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 2 ) Indicator (n) 3 Sample Specific Detection Limit for

Nitrate

- nitrite as N (mg/L)

Detection Limit = 0.1

Allen 1 FGD Purge (N = 8) D (n = 8) Bioreactor Influent (N = 8) D (n = 8)

Bioreactor Effluent (N = 8) D (n = 1)

ND (n = 7) 7

Belews Creek 1 FGD Purge (N = 8) D (n = 8) Bioreactor Influent (N = 8) D (n = 8)

Bioreactor Effluent (N = 8) D (n = 3)

ND (n = 5) 5

1 : Combination o f EPA sampling and CWA 308 sampling

. 2 : Detected and non

- detected observations combined.

3 : D = detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for nitrate

- nitrite as N concentrations by sampling location and plant.

Table 15 . Summary statistics of nitrate

- nitrite as N concentration (mg/L) for all detected and

non

- detected samples combined by plant and sampling location.

Plant Name Sampling Location Summary Statistics for Nitrate

- nitrite as N (mg/L)

N 2 Minimum Mean Median Maximum Std

Allen 1 FGD Purge 8 14.0 32.0 29.5 51.0 15.4

Bioreactor Influent 8 13.0 22.5 21.5 39.0 10.4

Bioreactor Effluent 8 0.1 0.1 0.1 0.13 0.01

Belews Creek 1 FGD Purge 8 14.0 16.6 15.5 21.0 2.7

Bioreactor Influent 8 12.0 17.1 17.5 21.0 3.1

Bioreactor Effluent 8 0.1 0.12 0.1 0.15 0.02

1 : Combination o f EPA sampling and CWA 308 sampling

. 2 : Detected and non

- detected observations combined.



### 7.3.3. Plant

- specific long

- term average s and variability factors, option long

- term average s and variability factors, and effluent limits for nitrate

- nitrite as N (mg/L)

The table below provides the plant

- specific long

- term averages

, plant

- specific variability factors, option long

- term averages, opt ion variability factors, and effluent limits for nitrate

nitri te as N at bioreactor effluent

.

### Page 41 

### Table 16 . Lag

- 1 autocorrelation values, plant

- specific long

- term averages and variability factors, option long

- term averages and variabi lity factors, and limits for nitrate

- nitrite as N (mg/L) at
bioreactor effluent.

TYPE Plant Name N 2 Autocorrelation
Value 3 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

Specific Allen 1 8 (D=1,ND=7) 0 0.104 4

-- 5

-- 5

0.291 0.104 4

-- 5

-- 5

Belews
Creek 1 8 (D=3,ND=5) 0 0.115 1.395 1.144

0.291 0.115 1.499 1.157

Option 0 0.1 09 1.395 1.144 0.153 0.125

0.291 0.110 1.499 1.157 0.164 0.127

1 : Combination o f EPA sampling and CWA 308 sampling

. 2 : D = detected and ND = non

- detected.

3 : Correlation ranges from

- 1 to 1, with a value of 0 indicating that EPA assumed no correlation in the data

. 4 : Long

- term average is the arithmetic mean since there were too few detected observations (not able to estimate the variance of the distribution).

5 : Nearly all observations were non

- detected, so the variability factors could not be calculated.



### 7.4

. Biological Treatment for FGD Wastewater : Selenium

7. 4 .1. Longitudinal plots of the data for selenium (ug/L)

Below are the l ongitudinal plots of the selenium concentrations (on a logarithmic scale)
for Allen and Belews Creek.

Figure 6 . Plot of selenium (ug/L) data on a logarithmic scale for Allen and Belews Creek.510505005000 Allen (logarithmic scale)

Date Note: Detected = o Non-Detected = *Selenium (ug/L)

Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 *

* * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * FGD Purge Bioreactor Inf. Bioreactor Eff.510505005000 Belews Creek (logarithmic scale)

Date Detected: o Non-Detected: *Selenium (ug/L)

Aug 08 Jan 09 Jun 09 Nov 09 Apr 10 Sep 10 Feb 11 * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * *

* * * * * * * FGD Purge Bioreactor Inf. Bioreactor Eff.

### Page 42 

### 7.4.2. Summary statistics for selenium (ug/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location and plant.

Table 17 . Number of detected, non

- detected, and sample

- specific detection limits for selenium (ug/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 2 ) Indicator (n) 3 Sample Specific Detection Limits for Selenium (ug/L)

5 10 15

Allen 1 FGD Purge (N = 63) D (n = 63)
Bioreactor Influent (N = 63) D (n = 63)

Bioreactor Effluent (N = 63) D (n = 4)

ND (n = 59) 54 5

Belews Creek 1 FGD Purge (N = 76) D (n = 76) Bioreactor Influent (N = 75) D (n = 75)

Bioreactor Effluent (N = 77) D (n = 26)

ND (n = 51) 23 27 1

1 : Combination o f EPA sampling , CWA 308 sampling , and plant self

- monitoring data.

2 : Detected and non

- detected observations combined.

3 : D = detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detecte d and non

detected combined) for selenium by sampling location and plant.

Table 18 . Summary statistics of selenium concentration (ug/L) for all detected and

non

- detected samples combined by plant and sampling location.

Plant Name Sampling Location Summary Statistics for Selenium (ug/L)

N 2 Minimum Mean Median Maximum Std

Allen 1 FGD Purge 63 849.0 1,685.2 1,660.0 3,260.0 452.1

Bioreactor Influent 63 57.7 324.0 113.0 1,140.0 322.6

Bioreactor Effluent 63 5.0 5.6 5.0 11.7 1.6

Belews Creek 1 FGD Purge 76 1,660.0 6,797.3 6,625.0 26,200.0 3,139.0

Bioreactor Influent 75 58.0 337.9 121.0 2,940.0 516.9

Bioreactor Effluent 77 5.0 9.4 10.0 29.4 5.1

1 : Combination o f EPA sampling , CWA 308 sampling , and plant self

- monitoring data.

2 : Detected and non

- detected observations combined.

### Page 43 

### 7.4 .3. Plant

- sp ecific long

- term average s and variability factors, option long

- term average s and variability factors, and effluent limits for selenium (ug/L)

The table below provides the plant

- specific long

- term averages

, plant

- specific variability factors, option long

- term averages, option variability factors, and effluent limits for selenium at bioreactor effluent

.

Table 19 . Lag

- 1 autocorrelation values, plant

- specific long

- term averages and variability factors, option long

- term averages and v ariability factors, and limits for selenium (ug/L) at bioreactor
effluent.

TYPE Plant

Name N 2 Autocor rel
ation
Value 3 LTA Daily Variability

Factor Monthly
Variabilit y Factor Limits

Daily Monthly

Plant

Specific Allen 1 63 (D=4, ND=59) 0 5.581 1.869 1.330

0.291 5.551 1.627 1.192
Belews
Creek 1 77 (D=26, ND=51) 0 9.444 3.249 1.536

0.291 9.359 2.663 1.450

Option 0 7.513 2.559 1.433 19.224 10.764

0.291 7.455 2.145 1.321 15.990 9.849

1 : Combination o f EPA sampling , CWA 308 sampling , and plant self

- monitoring data.

2 : D = detected and ND = non

- detected.

3 : Correlation ranges from

- 1 to 1, with a value of 0 indicating that EPA assum ed no correlation in the data.



### 7.5. Biological Treatment for FGD Wastewater: Summary of the Option Long

- Term Averages
, Variability Factors, and Effluent Limits

The table below summarizes the option long

- term average, option variability factors, and effluent limits for each pollutant for biological treatment technology option for FGD

wastewater

. It should be noted that the option long

- term averages and variability factors, and effluent limits p resented in previous tables also included values assuming zero autocorrelation

. However, the limits proposed for this rulemaking are based on the autocorrelation obtained
from the data

. The table below presents the results for the option long

- term averages , option variability factors, and daily maximum and monthly average limits that incorporated the
autocorrelations

. As described above, EPA is proposing to transfer the arsenic and mercury limits from the chemical precipitation technology option to biologic al technology option

. Thus, the table below presents the ars enic and mercury limits based on the chemical precipitation technology option.

### Page 44 

### Table 20 . Summary of option long

- term averages, variability factors, and effluent limits f or biological FGD wastewater treatment technology.

Pollutant Autocorrelati
on Value Option

LTA Option Daily Variability

Factor Option Monthly Variability

Factor Daily
Limit 2 Monthl y Limit 2



### Arsenic (ug/L) 1



### -- 4.483 1.741 1.223 8 6 Mercury (ng/L) 1



### -- 75.404 3.209 1.570 242 119

Nitrate

- n itrite as N (mg/L) 0.291 0.1 10 1.499 1.157 0.1 7 0. 13
Selenium (ug/L) 

### 0.291 7.455 2.145 1.321 16 10

1 : Long term average, variability factors, and limits were transferred from the chemical precipitation treatment technology option for FGD wastewater

. 2 : Effluent limitations greater than 1.0 have been rounded upward to the next highest integer. Effluent limitations less than 1.0 are rounded up to the next highest hundredths decimal place.



## 8

. Treatment Technology Option for FGD Wastewater: Vapor

- Compression Evaporation System

EPA used data from Brindi si power plant to calculate the effluent limits for the chemical precipitation followed by vapor

- compression evaporation treatment technology option for FGD

wastewate r

. The pollutant s for which the effluent limits are calculated are arsenic, mercury, selenium, and total dissolved solids.

The effluent limits were calculated for the following two sampling locations: (i) brine
concentrator d istillate and (ii) crystallizer condensate

. The proposing effluent limits for this technology option were based on the sampling location that produced the higher effluent
limits

. Setting the effluent limits on the higher concentration stream is necessary in this

instance to ensure plants operating a well

- designed and well

- operated evaporator system can
meet the effluent limits, regardless of whether they sample the effluent streams separately or

as a combined stream (see Section 13 of the Technical Development Docume nt for a detailed discussion).

Brindisi sampling data were collected by EPA between 04/05/2011 and 04/07/2011

. Data were available at the following sampling locations: FGD Purge, brine concentrator distillate , and crystallizer condensate.

EPA attempted to use the available data to estimate the autocorrelation

. However, for Brindisi, EPA was not able to perform an evaluation of the autocorrelation because there were
too few observations available at the plant

. Thus, EPA set the autocorrelation to zero in developing the limits for the reasons described in section 5.3

.

The s ections below provide the following for each of the pollutant s: longitudinal plots of the data, summary statistics, and plant

- specific long

- term average and variability factors (see Appendix B for an overview of the statistical model and the procedures used to estimate the

### Page 45 

### plant

- specific long term average and variability factors)

. S ince only one plant was used, the option long

- term average and option variability factors are the same as the plant

- specific long

term average and variability factors.

8.1. Vapor

- Compression Evaporation for FGD Wastewater : Arsenic

8.1.1. Longitudinal plots of the data for arsenic (ug/L)

Below is the longitudinal plot of the arsenic concentrations (on a logarithmic scale) for
Brindisi.

Figure 7 . Plot of arsenic (ug/L) data on a logarithmic scale for Brindisi.

8.1.2. Summary statistics for arsenic (ug/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits for each sample
location.5102050 Brindisi (logarithmic scale)

Date Note: Detected = o Non-Detected = *Arsenic (ug/L)

Apr-05-11 Apr-06-11 Apr-07-11 * * * FGD Purge Brine Conc. Dist. Crystallizer Condensate

### Page 46 

### Table 21 . Numbers of detected and non

- detected ob servations and sample

- specific detection limits for arsenic (ug/L) by sampling location.

Plant

Name Sampling Location (Total Observations 1 ) Indicator (n) 2 Sample Specific Detection Limits for Arsenic (ug/L)

Detection Limit = 4

Brindisi FGD Purge (N = 2) D (n=2) Brine Concentrator Distillate (N = 3) ND (n=3) 3 Crystallizer Condensate (N = 3) ND (n=3) 3

1 : Detected and non

- detected observations combined.

2 : D = detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for each of sampling location.

Table 22

. Summary statistics of arsenic concentration (ug/L) for all detected and non

- detected samples combined by sampling location.

Plant Name Sampling Location Summary Statistics for Arsenic (ug/L)

N 1 Minimu

m Mean Median Maximum Std

Brindisi FGD Purge 2 53.0 54.0 54.0 55 1.41

Brine Concentrator Distillate 3 4.0 4.0 4.0 4.0 0
Crystallizer Condensate 3 4.0 4.0 4.0 4.0 0

1 : Detected and non

- detected observations combined (all observations are non

- detected)

.



### 8.1.3. Plant

- specific long

- term average s and variability factors, option long

- term average s and
variabili ty factors, and effluent limits for arsenic (ug/L)

The table bel ow provides the plant

- specific long

- term average s and variability factors, option long

- term average s and variability factors, and effluent limits for arsenic at two sampling
locations: brine concentrator distillate and crystallizer condensate

.

Since all observations were non

- detected

, the statistical model was not used to obtain the long

- term average and variability factors (see Sections 5.4, 5.5, and 5.6)

. The daily limits for both sampling locations were set based on the detection limit

. The monthly ave rage limits are not established when the daily limit is set equal to the detection limit.

### Page 47 

### Table 23

. Plant

- specific long

- term averages and v ariability factors, option long

- term averages and variability factors, and limits for arsenic (ug/L) at brine concentrator distillate and crystallizer condensate.

Type Plant

Name Sampling
Location N 1 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

– Specific Brindisi Brine

Concentrator
Distillate 3 (D=0, ND=3) 4.0 2

-- 3

-- 3

Crystallizer
Condensate 3 (D=0, ND=3) 4.0 2

-- 3

-- 3

Option Brine

Concentrator
Distillate 4.0 2

-- 3

-- 3 4 4

-- 5

Crystallizer
Condensate 4.0 2

--- 3

-- 3 4 4

-- 5

1 : D = detected and ND = non

- d etected.

2 : Long

- term average is the arithmetic mean since all observations we re non

- detected (not able to estimate the variance of the distribution).

3 : A ll observations were non

- detected, so the variability factors could not be calculated.

4 : Limit is s et equal to the detection limit

. 5 : Monthly average limit is not established when the daily limit is equal to detection limit.



### 8.2. Vapor

- Compression Evaporation for FGD Wastewater: Mercury

8.2.1. Longitudinal plots of the data for mercury (ng/L)

Below is the longitudinal plot of the mercury concentrations (on a logarithmic scale) for
Brindisi.

Figure 8 . Plot of mercury (ng/L) data on a logarithmic scale for Brindisi.510505005000 Brindisi (logarithmic scale)

Date Note: Detected = o Non-Detected = *Mercury (ng/L)

Apr-05-11 Apr-06-11 Apr-07-11 FGD Purge Brine Conc. Dist. Crystallizer Condensate

### Page 48 

### 8.2.2. Summary statistics for mercury (ng/L)

All observations at each of the sampling locations for Brindisi were detected

. The table below provides summary statistics for all observations for each sampling location

.

Table 24 . Summary statistics of mercury concentration (ng/L ) for all detected and non

- detected samples combined by sampling location.

Plant Name Sampling Location Summary Statistics for Mercury (ng/L)

N 1 Minimum Mean Median Maximum Std

Brindisi FGD Purge 2 21,100.0 24,000.0 24,000.0 26,900.0 4,101.2

Brine Concentrator Distillate 3 2.9 3.3 3.1 4.0 0.6
Crystallizer C ondensate 3 10.9 17.3 20.4 20.7 5.6

1 : Detected and non

- detected observations combined (all observations were detected).



### 8.2.3. Plant

- specific long

- term average s and variability factors, option long

- term average s and variability factors, and effluent limits for mercury (ng/L)

The table below provides the plant

- specific LTAs and plant

- specific variability factors, option LTA s and variability factors, and limits for mercury at two sampling locations: brine
concentrator distillate and crystallizer condensate

.

Table 25

. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and limits for mercury (ng/L) at brine concentrator distillate and crystallizer condensate.

Type Plant

Name Sampling
Location N 1 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

– Specific Brindisi Brine

Concentrator
Distillate 3 (D=3, ND=0) 3.348 1.453 1.144

Crystallizer
Condensate 3 (D=3, ND=0) 17.788 2.192 1.338

Option Brine

Concentrator
Distillate 3.348 1.453 1.144 4.865 3.829

Crystallizer
Condensate 17.788 2.192 1.338 38.989 23.799

1 : D = detected and ND = non

- detected.

### Page 49 

### 8.3. Vapor

- Compression Evaporation for FGD Wastewater: Selenium

8.3 .1. Longitudinal plots of the data for selenium (ug/L)

Below is the longitudinal plot of the selenium concentrations (on a logarithmic scale) for
Brindisi.

Figure 9 . Plot of selenium (ug/L) data on a logarithmic scale for Brindisi.

8.3 .2. Summary statistics for selenium (ug/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location.

Table 26

. Number of detected, non

- detected, and sample

- specific detection limits for selenium (ug/L) by sampling location.

Plant

Name Sampling Location (Total Observations 1 ) Indicator (n) 2 Sample

- Specific Detection Limits for Selenium (ug/L)

Detection Limit = 5

Brindisi FGD Purge (N = 2) D (n = 2) Brine Concentrator Distillate (N = 3) ND (n = 3) 3 Crystallizer Condensate (N = 3) ND (n = 3) 3

1 : Detected and non

- detected observations combined.

2 : D = detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for each sampling location

.5102050100200 Brindisi (logarithmic scale)

Date Note: Detected = o Non-Detected = *Selenium (ug/L)

Apr-05-11 Apr-06-11 Apr-07-11 * * * FGD Purge Brine Conc. Dist. Crystallizer Condensate

### Page 50 

### Table 27 . Summary statistics of selenium concentration (ug/L) for all detected and

non

- detected samp les combined by sampling location.

Plant Name Sampling Location Summary Statistics for Selenium (ug/L)

N 1 Minimum Mean Median Maximum Std

Brindisi FGD Purge 2 220.0 255.0 255.0 290.0 49.5

Brine Concentrator Distillate 3 5.0 5.0 5.0 5.0 0.0
Crystallizer Condensate 3 5.0 5.0 5.0 5.0 0.0

1 : Detected and non

- detected observations combined (all observations were non

- detected).



### 8.3.3. Plant

- specific long

- term average s and variability factors, option long

- term average s and variability factors, and effluent limits for selenium (ug/L)

The table below provides the option plant

- specific LTA s and variability factors , option
LTAs and variability factors, an d effluent limits for selenium at two sampling locations: brine
concentrator distillate and crystallizer condensate.

All observations were non

- detected

, so the statistical model was not used to obtain the long

- term average and variability factors

. The daily limits for both sampling locations were set
based on the detection limit

. The monthly average is not set when the daily limit is based on
the detection limit

.

Table 28

. Plant

- specific long

- term averages and variability factors, option long

- term averages and variability factors, and l imits for s elenium (ug/L) at brine concentrator distillate and crystallizer condensate.

Type Plant

Name Sampling
Location N 1 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

– Specific Brindisi Brine

Concentrator
Distillate 3 (D=0, ND=3) 5.0 2

-- 3

-- 3

Crystallizer
Condensate 3 (D=0, ND=3) 5.0 2

-- 3

-- 3

Option Brine

Concentrator
Distillate 5.0 2

-- 3

-- 3 5 4

-- 5

Crystallizer
Condensate 5.0 2

-- 3

-- 3 5 4

-- 5

1 : D = detected and ND = non

- detected.

2 : Long

- term average is the arithmetic mean since all observations were non

- detected (not able to estimate the variance of the distribution).

3 : All observations were non

- detected, so the variability factors could not be calculated.

4 : Limitation is set equal to the detection limit.

5 : Monthly average limitation is not established when the daily limit is equal to detection limit.

### Page 51 

### 8.4. Vapor

- Compression Evaporation for FGD Wastewater: Total Dissolved Solids (TDS)

8.4 .1. Longitudinal plots of the data for TDS (mg/L)

Below is the lon gitudinal plot of the TDS concentrations (on a logarithmic scale) for
Brindisi.

Figure 10 . Plot of TDS (mg/L) data on a logarithmic scale for Brindisi.

8.4 .2. Summary statistics for TDS (mg/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location.

Table 29

. Number of detected, non

- detected, and sample

- specific detection limits for total dissolved solid (mg/L) by sampling location.

Plant

Name Sampling Location (Total Observations 1 ) Indicator (n) 2 Sample

- Specific Detection Limits for TDS (ug/L)

Detection Limit = 10

Brindisi FGD Purge (N = 2) D (n = 2)

Brine Concentrator Distillate (N = 3) D (n = 2)

ND (n = 1) 1 Crystallizer Condensate (N = 3) D (n = 2)

ND (n = 1) 1

1 : Detected and non

- detected observations combined.

2 : D = detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for each sampling location.10505005000 Brindisi (logarithmic scale)

Date Note: Detected = o Non-Detected = *TDS (mg/L)

Apr-05-11 Apr-06-11 Apr-07-11 * FGD Purge Brine Conc. Dist. Crystallizer Condensate

### Page 52 

### Table 30 . Summary statistics of total dissolved solids concentration (mg/L) for all detected and

non

- detected samples combined by sampling location.

Plant Name Sampling Location Summary Statistics for Total Dissolved Solids (mg/L)

N 1 Minimum Mean Median Maximu

m Std

Brindisi FGD Purge 2 13,000.0 14,000.0 14,000.0 15,000.0 1,414.2

Brine Concentrator Distillate 3 10.0 11.0 10.0 13.0 1.7
Crystallizer Condensate 3 10.0 14.0 10.0 22.0 6.9

1 : Detected and non

- detected observations combined.



### 8.4.3. Plant

- specific long

- term average s and variability factors, option long

- term average s and variability factors, and effluent limits for TDS (mg/L)

The table below provides the plant

- specific LTAs and variability factors, option LTA s and variability factors, and effluent limits for TDS at two sampling locations: brine concentrator
distillate and crystallizer condensate

.

Table 31

. Plant

- specific long

- term averages and v ariability factors, option long

- term averages and variability factors, and limits for TDS (mg/L) at bri ne concentrator distillate and crystallizer
condensate.

Type Plant

Name Sampling
Location N 1 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

– Specific Brindisi Brine

Concentrator
Distillate 3 (D=2, ND=1) 11.066 1.541 1.150

Crystallizer
Condensate 3 (D=2, ND=1) 14.884 3.341 1.572

Option Brine

Concentrator
Distillate 11.066 1.541 1.150 17.054 12.722

Crystallizer
Condensate 14.884 3.341 1.572 49.734 23.393

1 : D = detected and ND = non

- d etected.



### 8.5. Vapor

- Compression Evaporation for FGD Wastewate r: Summary of the Option Long

- Term Averages
, Option V ariability Factors, and Effluent Limits

T he t able s below summarize the option long

- term average, option variability factors,
and limits for each of the pollutants for the chemical precipitation followed by vapor compression evaporation system for FGD wastewater

. Table 3 2 provides the results for brine concentrator distillate sampling location while Table 33 provides the results at crystal lizer condensate sampling location

. S ince only one plant was used, the option LTA and option variability factors are the same as the plant

- specific LTA and variability factors

. Note that the

### Page 53 

### effluent limits for regulation for this technology option are ba sed on the crystallizer
condensate. See Section 13 of the Technical De velopment Document for a discussion of EPA’s reasons for basing the effluent limits for this technology option on the crystallizer condensate
rather than the effluent limits calculated a t brine concentrator distillate

.

Table 32

. Summary of option long

- term averages, variability factors, and limits for vapo r

compression evaporation technology for FGD wastewater at brine concentrator distillate.

Pollutant Autocorrelation
value Option

LTA Option Daily Variability

Factor Option Monthly Variability

Factor Daily
Limit 3 

### Monthly
Limit 3



### Arsenic (ug/L) 0 4.0 1



### --- 2



### --- 2 

### 4 4



### -- 5 

### Mercury (ng/L) 0 3.348 1.453 1.144 5 4 Selenium (ug/L) 0 5.0 1



### --- 2



### --- 2 

### 5 4



### -- 5 

### TDS (mg/L) 0 11.066 1.541 1.150 18 13

1 : Long

- term average is the arithmetic mean since all observations were non

- detected (not able to estimate the variance of the distribution).

2 : All observations were non

- detected, so variability factors could not be calculated.

3 : Effluent limitations greater than 1.0 have been rounded upward to the next highest integer.

4 : Limitation is s et equal to the detection limit

. 5 : Monthly average limit ation is not established when the daily limit is based on the detection limit.



### Table 33 . Summary of option long

- term averages, option variability factors, and limits for mechanical vapor

- compression evaporation technology for FGD wastewater at crystallizer
condensate.

Pollutant Autocorrel
ation value Option LTA Option Daily Variability

Factor Option Monthly Variability

Factor Daily
Limit 3 

### Monthly
Limit 3



### Arsenic (ug/L) 0 4.0 1



### --- 2



### --- 2 

### 4 4



### -- 5 

### Mercury (ng/L) 0 17.788 2.19 2 1.338 39 24 Selenium (ug/L) 0 5 .0 1



### --- 2



### --- 2 

### 5 4



### -- 5 

### TDS (mg/L) 0 14.88 4 3.34 1 1.57 2 50 24

1 : Long

- term average is the arithmetic mean since there were too few detected observations (not able to estimate the variance of the distribution).

2 : A ll observations were non

- detected, so the variability factors could not be calculated.

3 : Effluent limitations greater than 1.0 have been rounded upward to the next highest integer

. 4 : Limitation is set equal to the detection limit.

5 : Monthly average limitat ion is not established when the daily limit is based on the detection limit.

### Page 54 

## 9. Treatment Technology Option for Gasification Wastewater: Vapor

Compression Evaporation

EPA used data from two power plants (Polk and Wabash River) to develop the effluent
limits for the vapor

- compression evaporation treatment technology for gasification

wastewater

. The four pollutan ts for which the limits are calculated are arsenic, mercury, selenium, and total dissolved solids

. Arsenic and m ercury data at Wabash River failed the data editing criteria, thus, EPA excluded the arsenic and mercury data from this plant in developing the limits for gasification wastewater treatment technology

. Even though the Wabash River
data for arsenic and mercu ry were not used to develop the limits, summary statistics and plots for these two pollutants at this plant a re also presented in this section

.

For this technology option, EPA considered limits at two sampling locations: (i) forced circulation evaporator condensate and (ii) vapor compression evaporator condensate

. EPA is proposing to set the limits based on vapor compression evaporator condensate data since EPA determined that the data collected at forced circulation evaporator condensate did not
demonstr ate typical removal rates for pollutants generally well

- treated by evaporation and therefore were not adequate to form the basis of the limits. Based on its review of the treatment system, EPA believes that the evaporator (or at a minimum the forced circul ation evaporation stage) was operating abnormally and allowing carryover of pollutants to the condensate effluent stream. For this reason, EPA based the limits for this technology option on
the limits calculated from the vapor compression evaporator conden sate data (see Section 13 of the Technical Development Document). If EPA was to calculate limits using the data at the forced circulation evapora tor condensate, it would follow the same methodology used to
calculate the limits for vapor compression evaporator condensate data

.

The following provides a detailed summary of the available data for calculating th e numeric limits at each plant.

Polk Sampling Data

Polk sampling data were collected by the plant on the following dates : 10/18/2011, 10/19/201 1, 10/26/2011, and 10/27/2011. Data were available at the following sampling
locations: n eutralized weak acid, v apo r compression e vaporator influent, forced circulation evaporator condensate, and vapor c ompress ion evaporator condensa te.

Wabash River Sampling Data

Wabash River sampling data were collected by the plant between 02/21/2011 to 02/24/2011

. Data were available at the following sampling locations: sour water treatment influent, steam stripper effluent, vapor compression evaporator influent (RCC evaporator influent), and vapor compression evaporator condensate (RCC evaporator condensate)

.

### Page 55 

### EPA attempted to use the available data to estimate the autocorrelation

. However, for both of these plants, EPA was not able to perform an evaluation of the autocorrelation because
there were too few observations available at each plant

. Thus, EPA set that the autocorrelation
value is zero in the calculation of the lim its as de scribed in Section 5.3.

The sections below provide the following for each of the pollutant s: longitudinal plots of the data, summary statistics, and plant

- specific long

- term average and variability factors (see Appendix B for an overview of the statistica l model and the procedures used to estimate the plant

- specific long term average and variability factors)

. Also provided in the sections below are the option long

- term average, option variability factors, and effluent limits for each pollutant

.

9.1. Vapor

- Compression Evaporation for G asification : Arsenic

9.1.1. Longitudinal plots of the data for arsenic (ug/L)

Below are the longitudinal plots of the arsenic concentrations (on a logarithmic scale)
for Polk and Wabash River.

Figure 11 . Plot of arsenic (ug/L) data on a logarithmic scale for Polk and Wabash River.

9.1.2. Summary statistics for arsenic (ug/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location and plant.5102050100200 Polk (logarithmic scale)

Date Note: Detected = o Non-Detected = *Arsenic (ug/L)

Oct-18-11 Oct-19-11 Oct-26-11 Oct-27-11 * * * * Vapor Comp. Evap. Cond. Vapor Comp. Evap. Inf. Forced Circ. Evap. Cond.
Neut. Weak Acid Waste Stream5102050100200 Wabash River (logarithmic scale)

Date Detected: o Non-Detected: *Arsenic (ug/L)

Feb-21-11 Feb-22-11 Feb-23-11 Feb-24-1 * * * * * * * * * * Vapor Comp. Evap. Inf. Vapor Comp. Evap. Cond. Sour Water Trt. Inf. Steam Stripper Eff.

### Page 56 

### Table 34

. Numbers of detected and non

- detected observations and sample

- specific detection limits for arsenic (ug/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 1 ) Indicator (n) 2 Sample Specific Detection Limits for Arsenic (ug/L)

4 4.1 4.2

Polk Neu. Weak Acid Waste Stream (N = 4) D (n = 4)
Vapor Compr. Evap. Influent (N = 4) D (n = 4)
Vapor Compr. Evap. Condensate (N = 4) ND (n = 4) 4
Forced Cir. Evap. Condensate (N = 4) D (n = 4)

Wabash

River Sour Water Trt Influent (N = 4) ND (n = 4) 4
Steam Stripper Effluent (N = 4) ND (n = 4) 2 2

Vapor Compr. Evap. Influent (N = 4) D (n = 2)

ND (n = 2) 2
Vapor Compr. Evap. Condensate (N = 4) ND (n = 4) 4

1 : Detected and non

- detected observations combined.

2 : D = detected and ND = n on

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for each sampling location at each of the plants.

Table 35 . Summary statistics of arsenic concentration (ug/L) for all detected and non

- detected samples combined, by plant and sampling location.

Plant Name Sampling Location Summary St atistics for Arsenic (ug/L)

N 1 Minimum Mean Median Maximum Std

Polk Neu. Weak Acid Waste Stream 4 140.0 160.0 165.0 170.0 14.1
Vapor Compr. Evap. Influent 4 220.0 280.0 280.0 340.0 49.7
Vapor Compr. Evap.
Condensate 4 4.0 4.0 4.0 4.0 0.0
Forced Cir. Evap. Condensate 4 29.0 33.0 33.5 36.0 2.9

Wabash River Sour Water Trt Influent 4 4.1 4.1 4.1 4.1 0.0

Steam Stripper Effluent 4 4.1 4.2 4.2 4.2 0.1

Vapor Compr. Evap. Influent 4 4.0 4.5 4.5 5.0 0.6

Vapor Compr. Evap.
Condensate 4 4.0 4.0 4.0 4.0 0.0

1 : Detected and non

- detected observations combined.



### 9.1.3. Plant

- specific long

- term average and variability factors, option long

- term average and variability factors, and effluent limits for arsenic (ug/L)

The table below provides the plant

- specific LTA, plant

- specific variability factors, option LTA and variability factors, and numeric limits for arsenic at vapor c ompression evaporator
condensate (us ing Polk data only). As described above, the arsenic data for Wabash River failed

### Page 57 

### the d ata editing criteria, so , EPA excluded the arsenic dataset from Wabash River in developing the limits for this technology option.

Table 36 . P lant

- specific long

- term average and variability fa ctors, option long

- term average and

vari ability factors, and limits for arsenic (ug/L) at vapor compression evaporator condensate

.

TYPE Plant

Name Sampling Location

N 1 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

Specific Polk Vapor Compr Evap. Condensate 4 (D=0,ND=4) 4.00 2

-- 3

-- 3

Option Vapor Compr. Evap. Condensate 4.00 2

-- 3

-- 3 4 4

-- 5

1 : D = detected and ND = n on

- detected

. 2 : Long

- term average is the arithmetic mean since all observations were non

- detected (not able to estimate the variance of the distribution).

3 : A ll observations were non

- detected, so the variability factors could not be calculated.

4 : Limitation is set equal to the detection limit.

5 : Monthly average limitation is not established when the daily limit is equal to the detection limit

.



### 9.2

. Vapor

- Compression Evaporation for Gasification: Mercury

9.2.1. Longitudinal plots of the data for mercury (ng/L)

Below are the l ongitudinal plots of the mercury concentrations (on a logarithmic scale)
for Polk and Wabash River.

Figure 12 . Plot of mercury (ng/L) data on a logarithmic scale for Polk and Wabash River.

9.2.2. Summary statistics for mercury (ng/L)110100100010000 Polk (logarithmic scale)

Date Note: Detected = o Non-Detected = *Mercury (ng/L)

Oct-18-11 Oct-19-11 Oct-26-11 Oct-27-11 Vapor Comp. Evap. Cond. Vapor Comp. Evap. Inf. Forced Circ. Evap. Cond.
Neut. Weak Acid Waste Stream110100100010000 Wabash River (logarithmic scale)

Date Detected: o Non-Detected: *Mercury (ng/L)

Feb-21-11 Feb-22-11 Feb-23-11 Feb-24-1 * *

* * * * *

* * * Vapor Comp. Evap. Inf. Vapor Comp. Evap. Cond. Sour Water Trt. Inf. Steam Stripper Eff.

### Page 58 

### The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location and plant.

Table 37 . Numbers of detected and non

- detected observations and sample

- specific detection limits for mercury (ng/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 1 ) Indicator (n) 2 Sample Speci fic Detection Limits for

M ercury (ng/L)

0.5 4.95 9.9

Polk Neu. Weak Acid Waste Stream (N = 4) D (n = 4) Vapor Compr. Evap. Influent (N = 4) D (n = 4) Vapor Compr. Evap. Condensate (N = 4) D (n = 4) Forced Cir. Evap. Condensate (N = 4) D (n = 4)

Wabash

River Sour Water Trt Influent (N = 4) D (n = 3)

ND (n = 1) 1

Steam Stripper Effluent (N = 4) D (n = 2)

ND (n = 2) 2
Vapor Compr. Evap. Influent (N = 4) ND (n = 4) 1 3
Vapor Compr. Evap. Condensate (N = 4) ND (n = 4) 4

1 : Detected and non

- detected observations combined.

2 : D = detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for each sampling location at each of the plants.

Table 38 . Summary statistics of mercury concentration (ng/L) for all detected and non

- detected samples combined, by plant and sampling location.

Plant Name Sampling Location Summary Statistics fo r M ercury (ng/L)

N 1 Minimum Mean Median Maximum Std

Polk Neu. Weak Acid Waste Stream 4 2,030.0 4,392.5 2,270.0 11,000.0 4,408.9
Vapor Compr. Evap. Influent 4 17.0 70.4 85.9 92.7 36.1
Vapor Compr. Evap.
Condensate 4 0.8 1.1 1.1 1.3 0.2
Forced Cir. Evap. Condensate 4 5.0 6.1 5.7 8.0 1.3

Wabash River Sour Water Trt Influent 4 9.9 1,872.3 29.6 7,420.0 3,698.5

Steam Stripper Effluent 4 9.9 22.6 17.2 46.3 17.2

Vapor Compr. Evap. Influent 4 5.0 8.7 9.9 9.9 2.5
Vapor Compr. Evap.
Condensate 4 0.5 0.5 0.5 0.5 0.0

1 : Detected and non

- detected observations combined.



### 9.2.3. Plant

- specific long

- term average and variability factors, option long

- term average and variability factors, and effluent limits for mercury (ng/L)

### Page 59 

### The table below provides the plant

- specific LTA, plant

- specific variability factors, option
LTA and variability factors, and effluent limits for mercury at vapor c ompression evaporator
condensate (us ing Polk data only )

. Because the mercury data at Wabash River failed the data editing criteria, EPA excluded the data in developing the limits for this technology option

. Thus, the mercury limits are based on Polk data only

.

Table 39 . P lant

- specific long

- term average and variability fa ctors, option long

- term average and variability factors, and limits for mercury (ng/L) at vapor compression evaporator condensate

.

1 : D = detected and ND = n on

- detected.



### 9.3

. Vapor

- Compression Evaporation for Gasification: Selenium

9.3.1. Longitudinal plots of the data for selenium (ug/L)

Below are the l ongitudinal plots of the selenium concentrations (on a logarithmic scale)
for Polk and Wabash River.

Figure 13 . Plot of selenium (ug/L) data on a logarithmic scale for Polk and Wabash River.510505005000 Polk (logarithmic scale)

Date Note: Detected = o Non-Detected = *Selenium (ug/L)

Oct-18-11 Oct-19-11 Oct-26-11 Oct-27-11 Vapor Comp. Evap. Cond. Vapor Comp. Evap. Inf. Forced Circ. Evap. Cond.
Neut. Weak Acid Waste Stream510505005000 Wabash River (logarithmic scale)

Date Detected: o Non-Detected: *Selenium (ug/L)

Feb-21-11 Feb-22-11 Feb-23-11 Feb-24-1 * * * Vapor Comp. Evap. Inf. Vapor Comp. Evap. Cond. Sour Water Trt. Inf. Steam Stripper Eff. TYPE Plant

Nam e Sampling Location

N 1 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

Specific Polk Vapor Compr Evap. Condensate 4 (D=4,ND=0) 1.075 1.632 1.194

Option Vapor Compr. Evap. Condensate 1.075 1.632 1.194 1.754 1.284

### Page 60 

### 9.3.2. Summary statistics for selenium (ug/L)

The table below pro vides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location and plant.

Table 40 . Numbers of detected and non

- detected observations and sam ple

- specific detection limits for selenium (ug/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 1 ) Indicator 2 Sample

- Specific Detection Limits for Selenium (ug/L)

Detection Limit = 5

Polk Neu. Weak Acid Waste Stream (N = 4) D (n = 4) Vapor Compr. Evap. Influent (N = 4) D (n = 4) Vapor Compr. Evap. Condensate (N = 4) D (n = 4) Forced Cir. Evap. Condensate (N = 4) D (n = 4)

Wabash

River Sour Water Trt Influent (N = 4) D (n = 4)

Steam Stripper Effluent (N = 4) D (n = 4)
Vapor Compr. Evap. Influent (N = 4) D (n = 4)

Vapor Compr. Evap. Condensate (N = 4) D (n = 1)

ND (n = 3) 3

1 : Detected and non

- detected observations combined.

2 : D = detected and ND = n on

- detected.



### The table below provides summary statistics for all observations for each sampling location at each of the plants.

Table 41 . Summary statistics of selenium concentration (ug/L) for all detected and

non

- detected samples combined, by plant and sampling location.

Plant Name Sampling Location Summary Statistics for S elenium (ug/L)

N 1 Minimum Mean Median Maximum Std

Polk Neu. Weak Acid Waste Stream 4 6,000.0 7,550.0 7,350.0 9,500.0 1,515.5
Vapor Compr. Evap. Influent 4 720.0 1,277.5 1,295.0 1,800.0 551.5
Vapor Compr. Evap.
Condensate 4 140.0 277.5 250.0 470.0 149.7
Forced Cir. Evap. Condensate 4 2,500.0 2,675.0 2,650.0 2,900.0 170.8

Wabash River Sour Water Trt Influent 4 420.0 480.0 485.0 530.0 46.9

Steam Stripper Effluent 4 49.0 152.3 165.0 230.0 75.5
Vapor Compr. Evap. Influent 4 800.0 920.0 890.0 1,100.0 128.3
Vapor Compr. Evap.
Condensate 4 5.0 5.1 5.0 5.5 0.3

1 : Detected and non

- detected observations combined (all were detected)

.

### Page 61 

### 9.3.3. Plant

- specific long

- term average s and variability factors, option long

- term average and variability factors, and effluent limits for selenium (ug/L)

The table below provides the plant

- specific LTA, plant

- specific variability factors, option LTA and variability factors, and numeric limits for selenium at vapor compression evapora tor condensate (us ing both Polk and Wabash River data ).

Table 42 . Plant

- specific long

- term averages and variability fa ctors, option long

- term average and variability facto rs, and limits for selenium (ug/L) at vapor compression evaporator
condensate

.

TYPE Plant

Name Sampling Location

N 2 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

Specific Polk Vapor Compr Evap.
Condensate 4 (D=4,ND=0) 288.430 3.083 1.545

Wabash

River Vapor Compr Evap.
Condensate 4 (D=1,ND=3) 5.130

-- 3

-- 3

Option Vapor Compr. Evap. Condensate 1 146.780 3.083 1.545 452.560 226.810

1 : Polk and Wabash River combined.

2 : D = detected and ND = non

- detected

3 : Nearly all observations were non

- detected, so the variability factors could not be calculated.



### 9.4. Vapor

- Compression Evaporation for Gasification: Total Dissolved Solids (TDS)

9.4.1. Longitudinal plots of the data for TDS (mg/L)

Below are the l ongitudinal plots of the TDS concentrations (on a logarithmic scale) for
Polk and Wabash River.

Figure 14 . Plot of TDS (mg/L) data on a logarithmic scale for Polk and Wabash River.10505005000 Polk (logarithmic scale)

Date Note: Detected = o Non-Detected = *TDS (mg/L)

Oct-18-11 Oct-19-11 Oct-26-11 Oct-27-11 Vapor Comp. Evap. Cond. Vapor Comp. Evap. Inf. Forced Circ. Evap. Cond.
Neut. Weak Acid Waste Stream10505005000 Wabash River (logarithmic scale)

Date Detected: o Non-Detected: *TDS (mg/L)

Feb-21-11 Feb-22-11 Feb-23-11 Feb-24-1 * *

* * Vapor Comp. Evap. Inf. Vapor Comp. Evap. Cond. Sour Water Trt. Inf. Steam Stripper Eff.

### Page 62 

### 9.4.2. Summary statistics for TDS (mg/L)

The table below provides summary statistics for the numbers of detected and non

detected observations together with the sample

- specific detection limits by sample location and plant.

Table 43 . Numbers of detected and non

- de tected observations and sample

- specific detection limits for TDS (mg/L) by plant and sampling location.

Plant Name Sampling Location (Total Observations 1 ) Indicator (n) 2 Sample

- Specific Detection Limits for TDS (mg/L)

10 200

Polk Neu. Weak Acid Waste Stream (N = 4) D (n = 4) Vapor Compr. Evap. Influent (N = 4) D (n = 4) Vapor Compr. Evap. Condensate (N = 4) D (n = 4) Forced Cir. Evap. Condensate (N = 4) D (n = 4)

Wabash

River Sour Water Trt Influent (N = 4) D (n = 2)

ND (n = 2) 2
Steam Stripper Effluent (N = 4) D (n = 4)
Vapor Compr. Evap. Influent (N = 4) D (n = 4)

Vapor Compr. Evap. Condensate (N = 4) D (n = 2)

ND (n = 2) 2

1 : Detected and non

- detected observations combined.

2 : D =detected and ND = non

- detected.



### The table below provides summary statistics for all observations (detected and non

detected combined) for each sampling location at each of the plants.

Table 44

. Summary statistics of TDS concentration (mg/L) for all detected and non

- detected samples combined, by plant and sampling location.

Plant

Name Sampling Location Summary Statistics for TDS (mg/L)

N 1 Minimum Mean Median Maximum Std

Polk Neu. Weak Acid Waste Stream 4 26,000.0 27,250.0 26,000.0 31,000.0 2,500.0
Vapor Compr. Evap. Influent 4 4,500.0 4,575.0 4,600.0 4,600.0 50.0
Vapor Compr. Evap. Condensate 4 11.0 16.3 15.5 23.0 5.7
Forced Cir. Evap. Condensate 4 48.0 106.5 114.0 150.0 44.5

Wabash

River Sour Water Trt Influent 4 200.0 245.0 210.0 360.0 77.2

Steam Stripper Effluent 4 2,000.0 2,800.0 2,400.0 4,400.0 1,095.4

Vapor Compr. Evap. Influent 4 3,600.0 4,225.0 4,400.0 4,500.0 419.3
Vapor Compr. Evap. Condensate 4 10.0 13.5 11.0 22.0 5.7

1 : Detected and non

- detected observations combined

### Page 63 

### 9.4.3. Plant

- specific long

- term average s and variability factors, option long

- term average and variability factors, and effluent limits for TDS (mg/L)

The table below provides the plant

- specific LTA, plant

- specific variability factors, option LTA and variability factors, and numeric limits for TDS at vapor compression evaporator
condensate (us ing both Polk and Wabash River data ).

Table 45 . Plant

- specific long

- term averages and variability fa ctors, option long

- term average and variability factors, and numeric limits for TDS (mg/L) at vapor compression evaporator
condensate

.

TYPE Plant

Name Sampling Location N 2 LTA Daily Variability

Factor Monthly Variability

Factor Limits

Daily Monthly

Plant

Specific Polk Vapor Compr Evap.
Condensate 4 (D=4,ND=0) 16.512 2.149 1.327

Wabash

River Vapor Compr. Evap.
Condensate 4 (D=2,ND=2) 13.906 2.818 1.450

Option Vapor Compr. Evap.
Condensate 1 15.209 2.483 1.389 37.767 21.122

1 : Polk and Wabash River combined.

2 : D = detected and ND = non

- detected



### 9 .5 . Vapor

- Compression Evaporation for Gasification : Summary of the Option Long

- Term Average
, Option Variability Factors, and Effluent Limits

The table below summarize s the option long

- term average s , option variability factors, and effluent limits for vapor compression

- evaporation technology option

. Note that EPA is proposing that the daily and monthly average limitations for mercury for gasification wastewater be rounded to two decimal places instead of rounding to the next highest integer in order to avoid having the same value for the daily and monthly average limitation.

Table 46

. Su mmary of option long

- term averages

, option v ariability factors, and limits for vapor

compression evaporation technology for gasification wastewater

.

Pollutant Autocorrelati
on Value Option

LTA Option Daily Variability

Factor Option Monthly Variability

Factor Daily
Limit 3 Monthly
Limit 3

Arsenic (ug/L) 0 4.0 1

-- 2

-- 2 4 4

-- 5 Mercury (ng/L) 0 1.075 1.632 1.194 1.76 1.29 Selenium (ug/L) 0 146.780 3.083 1.545 453 227 TDS (mg/L) 0 15.209 2.483 1.389 38 22

1 : Long

- term average is the arithmetic mean since all observations were non

- detected (not able to estimate the variance of the distribution).

2 : All observations were non

- detected, so the variability factors could not be calculated.

3 : : Effluent limitations greater than 1.0 have been rounded upw ar d to the next highest integer, except for limits for mercury, which were rounded to the next highest hundredths decimal place.

4 : Limit is set equal to the detection limit.

5 : Monthly average limits are not established when the daily maximum limitation is based on the detection limit.

### Page 64 

## 10. Summary of Effluent Limits for Each Treatment Technology Option for FGD, Gasification, and Leachate Wastewater

Sections 6, 7, 8, and 9 above present detailed summary statistics of the data together with the long

- term averages, variability factors, and effluent limits for each treatment technology option for FGD and gasification wastewaters

. This section provides an overall summary of the option long

- term average s , option variability factors, and limits for each
technol ogy option presented in Sections 6, 7, 8, and 9 above

. In addition, this section also summarizes the regulation for leachate

.

The bullets below provide some important items that are discussed both in previous

secti ons and again in this section.

**•** EPA is proposing to transfer the effluent limits for arsenic and mercury calculated from the chemical precipitation technology option for the FGD to the biolo gical technology option for FGD (see Section 13 of the TDD for the rationale for this transfer of limits)

.

**•**



### • For chemical precipitation followed by vapor

- compression evaporation treatment technology option for FGD wastewater, the effluent limits were based on the data from crystallizer condensate sampling location

. As explained in Section 8 above, EPA
calculat ed limits for this technology option at two separate sampling locations: (i) brine
concentrator d istillate and (ii) crystallizer condensate

. The limits selected for the rulemaking were based on the stream (i.e., crystallizer condensate) with the higher pol lutant concentrations

.

**•**



### • For leachate effluent limits based on chemical precipitation technology option, EPA is transferring the effluent limits from the chemical precipitation technology option for
FGD wastewater because EPA does not have available efflue nt data for chemical precipitation treatment of combustion residual leachate.

**•** In most cases, the limits greater than 1.0 were rounded upward to the next highest integer, while limits less than 1.0 were rounded up to the next highest hundredths
decimal place. For mercury for gasification wastewater, after performing the rounding, the daily and monthly average limits for mercury for gasification wastewater were the same (i.e., both were 2 since the pre

- rounded daily and monthly average limitations were 1.754 and 1.284, respectively)

. Thus, in order to avoid having the same value for the daily and monthly average limit, EPA is proposi ng that the daily and monthly average limitations for mercury for gasification wastewater be rounded to two decimal place s.

The table below provides the proposed option long

- term average, option variability factors, and limitations for each of the FGD, ga sification, and leachate technology options.

### Page 65 

### Table 47 . Summary of the option long

- term average s and variability factor s together with the
effluent limits for each of the FGD, gasif ication, and leachate technology option

.

Treatme nt Technology Option Pollutant Autocorre
lation
Value Option LTA Daily Variability

Factor Monthly Variability

Factor Daily
Limitati

on 4 Monthl

y Limitati

on 4

Chemical Precipitation For

FGD Arsenic (ug/L) 0 

### 4.483 1.741 1.223 8 6

Mercury (ng/L) 0 

### 75.404 3.209 1.570 242 119

Chemical Precipitation
and Biological

Treatment For

FGD Arsenic (ug/L) 1

- 

### 4.483 1.741 1.223 8 6
Mercury (ng/L) 1

- 

### 75.404 3.209 1.570 242 119

Nitrate

- nitrite (mg/L) 0.291 

### 0.110 1.499 1.157 0.17 0.13

Selenium (ug/L) 0.291 

### 7.455 2.145 1.321 16 10

Chemical Precipitation
and Evaporation for FGD Arsenic (ug/L) 0 

### 4.0 2



### --- 3



### --- 3 

### 4 5



### -- 6
Mercury (ng/L) 0 

### 17.788 2.192 1.338 39 24 Selenium (ug/L) 0 

### 5.0 2



### --- 3



### --- 3 

### 5 5



### -- 6

TDS (mg/L) 0 

### 14.884 3.341 1.572 50 24

Vapor

Compression Evaporation for Gasification Arsenic (ug/L) 0 

### 4.0 2



### -- 3



### -- 3 

### 4 5



### -- 6

Mercury (ng/L) 0 

### 1.075 1.632 1.194 1.7 6 1.2 9
Selenium (ug/L) 0 

### 146.780 3.083 1.545 453 227
TDS (mg/L) 0 

### 15.209 2.483 1.389 38 22

Chemical Precipitation for
Leachate Arsenic (ug/L) 1

-- 

### 4.483 1.741 1.223 8 6

Mercury (ng/L) 1

-- 

### 75.404 3.209 1.570 242 119

1 : Option LTA, option variability factors, and effluent limits were transferred from chemical precipitation technology option for FGD wastewater.

2 : Long

- term average is the arithmetic mean since all observations were non

- detected.

3 : All observations were non

- detected, so variability factors could not be calculated.

4 : Effluent limit s less than 1.0 are rounded up to the next hig hest hundredths decimal place.

E ffluent limit s greater than 1.0 have been rounded upward to the next highest integer, except for e ffluent limit s for mercury based on the vapor

- compression evaporation treatment technology option for gasification wastewater which have been rounded up to the next highest hundredths decimal place.

5 : Limit is set equal to the detection limit.

6 : Monthly average limits are not established when the daily maximum limitation is based on the detection limit.

### Page 66 

## 11. Engineering Review of the Effluent Limit s

EPA has performed an engineering review to verify that the effluent limits are reasonable based upon the design and expected operation of the control technologies

. As part of this review, two types of comparisons were performed

. First, a comparison was made
between the effluent limits and the effluent data used to develop the limits

. This type of comparison helps to evaluate how reasonable the limits are from an engineering perspective

. Second, a comparison was made bet ween the limits and the influent data

. This comparison helps evaluate whether the proposed limits are set at a level that ensures that treatment of the wastewater would be necessary to meet the limits and that the influent concentrations were generally wel l

- contr olled by the treatment system.

Section 11.1 presents the results of the comparisons between the limits and all effluent
data that were used to calculate the limits for each technology option

. Section 11.2 presents the results of the comparisons bet ween the effluent limits and the influent data values for each technology option

. See Appendix 4 for a listing of all daily effluent values that are above the daily and monthly average limits (along with any other daily values collected in the same month).

11.1. Comparison of the Limits to Effluent Data Used as the Basis for the Limit s

As part of its data evaluations, EPA compared the value of the effluent limit s to the
effluent values used to calculate the limits . This type of comparison helps to evaluat e how
reasonable the limits are from an engineering perspective

. Since EPA is proposing both daily and monthly average limit s, EPA has performed two comparisons for each pollutant in each technology option

. EPA first compared the proposed daily limit s to the daily effluent values. Second, EPA compared the proposed monthly average limit s to all the effluent daily values, and identified those months where at least one value within a month exceeded the proposed monthly average limit s.

After thoroughly evaluating the results of the comparison between the limit s and the
effluent values used to calculate the limit s for each treatment technology option for FGD and gasification wastewaters, EPA determined that the statistical distributional assumptions used to develop the limit s are appropriate for the data, and thus the proposed limit s for each technology option are reasonable. (This conclusion is also true for the leachate limit s based on the chemical precipitation technology since the leachate limit s were transferred from the FGD

wastewater technology option .) If a plant properly designs and operates its wastewater treatment system to achieve the option long

- term average for the model technology (rather than targeting performance at the effluent limits the mselves) , it will be able to comply with the
limit s

. The sections below discuss the results of the comparisons for each of the technology option s

.

### Page 67 

### Chemical Precipitation Treatment Technology Option for FGD Wastewater

For the chemical precipitation treatment technology option for FGD wastewater, EPA is proposing limits for arsenic and mercury. The limits were calculated using data from three plants: Hatfield’s Fe rry, Keystone, and Miami Fort.

For both arsenic and mercury, there are some daily efflue nt concentration values that are above both the daily and monthly average limits. After thoroughly examining the data, EPA determined that the concentration values that are above both the daily and monthly limits for arsenic came from the plant with relati vely higher effluent concentration values (i.e., with a higher long

- term average than the other two plants)

. EPA observed that the same was true for the mercury concentration values that are above both the daily and monthly li mits . Since the
limits are developed using the data from all three plants, it is reasonable to expect that the plant with relatively higher concentrations is more likely to have values above the daily and monthly limits

. As EPA explains below in this section, it is reasonable for th is situation to arise in the datasets used to calculate the limits and there are specific steps plants can take that enable them to improve treatment system performance so that effluent concentrations would be in compliance with the proposed limits at all times.

EPA also identified an instance where two (of four) daily values in a month are higher than the monthly l imit , and the resulting monthly average is equal t o the monthly average limit

. Instances such as this (i.e., where one or more individual resul ts are higher than the monthly limitation, but the average of all results in a month are equal to or below the monthly limitation) are normal and consistent with the way effluent limits are calculated and implemented in NPDES permits. This is illustrated, in fact, by the selenium data for the biological treatment technology option, as described in the next section

. EPA also identified some cases where only one sample was taken during a month and the resulting concentration
value for that l one sample is abo ve the monthly limit

. In such cases, additional monitoring of the effluent (e.g., at weekly intervals) would likely result in a monthly average that would fall below the monthly average limit

.

In addition, EPA identified one month where two (out of four) daily concentration values from the month are above the monthly average limit , and the resulting monthly average for all four values is above the monthly limit

. Based on its engineering judgment developed over years of evaluating wastewater treatment proce sses for power plants and other industrial sectors, EPA determined that the combination of additional monitoring, closer operator attention, and optimizing treatment system performance to target the effluent concentrations at the technology option long

- ter m average will result in lower effluent concentrations that would be in compliance with the proposed effluent limits

.

EPA noted that while these plants were selected as representing the “best available” technology, it does not mean that the plants have th e systems fully optimized, especially since most of the plants do not have specific limits on the FGD wastewater for the pollutants of concern or because their existing limits are well above what the system is achieving.

### Page 68 

### Specifically, none of these three p lants have specific limits for arsenic. Also, only Keystone and Hatfield’s Ferry have NPDES permit limits on mercury; however, their current permit limits are more than 30 times higher than the proposed BAT effluent limits

. For this reason, these plants

cu rrently do not need to closely monitor the treatment system to confirm performance below their permit limit

. If these plants were required to meet the proposed limits , EPA believes that these plants would be capable of meeting the limits without significan t expense

. For example, EPA’s review of chemical precipitation systems for this industry noted that plants could benefit from using an in

- house mercury analyzer to monitor the performance of the system on a daily basis. Mercury analyzers have been effectiv ely used at a power plant to alert operators when mercury concentrations begin trending upward so that they may take steps to adjust treatment system performance and remain in compliance with their NPDES permit limits. Furthermore, some plants that rely so lely on hydroxide precipitation could add sulfide precipitation to improve removals of arsenic and mercury. Organosulfide addition, particularly using long

- chain organosulfide polymers, has been demonstrated to be particularly effective at improving

mercur y removals in chemical precipitation treatment systems. Finally, EPA has also evaluated the results of testing at a power plant that, although its FGD wastewater treatment system had been in operation for more than a year and was operating at a steady stat e condition, the plant significantly improved the pollutant removal performance merely by altering the dosage rates
for the wastewater treatment chemical additives

. As a result, EPA identified various approaches plants can use to improve their performance and achieve the limits

. EPA notes that its compliance cost estimate s for the proposed rule include costs for mercury analyzers, sulfide precipitation, and proper dosing of treatm ent system chemical additives.

Based on the results of the comparisons descri bed above, EPA determined that the statistical distributional assumption s are appropriate for the effluent data and that the proposed limits are reasonable.

Chemical Precipitation Followed by Biological Treatment Technology Option for FGD

Wastewater

For the biological treatment technology option for FGD wastewater, EPA is proposing limits for arsenic, mercury, nitrate

- nitrite as N, and selenium. For arsenic and mercury, EPA transferred the limits from the chemical precipitation treatment system for FGD wa stewater ( see Section 13 of the Technical Development Document)

. Because the limits for arsenic and mercury were transferred and since this technology option includes chemical precipitation as a first step, the comparison described above for the chemical precipitation technology option is
relevant for arsenic and mercu ry

. Because of this, EPA expects that the plants employing this technology option would be able to comply with the proposed arsenic and mercury limits. Furthermore, EPA’s data demonstrate that the biological treatment stage provides pollutant
reductions fo r arsenic and mercury (and other pollutants of concern with similar removal mechanisms) in addition to the pollutant removals that occur in the chemical precipitation stage of the biological treatment technology option (see, e.g., Sections 7.1 and 7.2). Th us, plants employing and optimally operating all components of the biological treatment technology option (including adding organosulfide to achieve sulfide precipitation) should

### Page 69 

### achieve pollutant removals for arsenic and mercury (and other pollutants with similar removal mechanisms) that are equal to or even greater than the removals based on chemical precipitation technology.

For nitrate

- nitrite as N at Allen, all daily effluent values are below both the daily and monthly limits

. For nitrate

- nitrite as N at Belews Creek, all daily effluent value s are below the daily limit

. However, there are two nitrate

- nitrite as N daily effluent values in different months
that are above the monthly limit . In each case only one sample was collected during the month

. As e xplained above for the chemical precipitation technology option and demonstrated in the following paragraph, additional effluent monitoring (e.g., at weekly intervals) would likely result in a monthly average that would f all below the monthly limit

.

For s elenium at Allen, all daily effluent concentration value s are below the daily limit

. Only one daily effluent value (out of two collected in the same month) for Allen is above the monthly limit

. However, after averaging these two observations, the average f or the month is below the monthly limit

. All other daily concentration values for Allen, spanning the period from September 2009 through May 2011, are belo w the average monthly limit

.

For selenium at Belews Creek, there are some daily effluent observatio ns that are above both the daily and monthly limits. After thoroughly examining the data, EPA determined that the effluent concentration values at Belews Creek are relatively higher (i.e., with a higher long

term average) than the effluent concentration va lues at Allen

. As discussed above, since the limits are developed using the data from both plants, it is reasonable to expect that the plant with relatively higher concentrations is more likely to have values above the daily and monthly
limits

. Furthermore , as EPA explained above

, there are steps plants can take to achieve better treatment system performance to ensure compliance with the effluent limits

. EPA indentified instances in which some daily effluent values at Belews Creek are above the average m ont hly
limit . However, these are the only values that were collected within each of those months

. As described above, additional effluent monitoring (e.g., at weekly intervals) would likely result in a monthly average that would fall below the monthly li mit

. EPA also identified four instances where some (or all) daily values from a month are above the monthly limit , but the daily values for other samples collected within the month are below the monthly limit

. In these instances, the average for all samples col lected within the month is above the monthly limit . Three of these four instances occur in the first three months of operation (August

– October 2008) following the end of the initial commissioning period for the treatment system. The Belews
Creek FGD wastew ater treatment system was the first FGD bioreactor system operated by Duke Energy, and one of the first two systems to begin operating in the U.S. After evaluating all selenium data for the biological treatment technology option (nearly three years of data for Belews Creek and nearly two years for Allen, excluding the initial commissioning periods), EPA concluded that the selenium results for August

- October 2008 reflect less than optimum performance of the treatment system due either to the inexperience of operators with this type of treatment system, or to continued variability associated with the initial commissioning of the

### Page 70 

### treatment system, or a combination thereof 2



### . Based on the results of this comparison for the biological trea tment technology option u sing the data from Allen and Belews Creek, EPA
determined that the statisti cal distributional assumptions are appropriate for the effluent data and that the proposed limits are reasonable.

Chemical Precipitation Followed By Vapor

- Compression Evaporator Treatment Technology Option for FGD Wastewater

For the vapor

- compression evaporation treatment technology option for FGD wastewater, EPA developed limits for arsenic, mercury, selenium and TDS. The limits were calculated using data from Brindisi plant

. Al l daily concentration values are below the daily and monthly limits

. After thoroughly reviewing the data, EPA determined that the statistical distributional assumption s are appropriate for the effluent data and that the proposed limits
are reasonable.

Vap or

- Compression Evaporator Treatment Technology Option for Gasification Wastewater

For the vapor

- compression evaporation treatment technology option for gasification wastewater, EPA is proposing limits for arsenic, mercury, selenium and TDS

. The limits wer e calculated using data from both the Polk and Wabash River plants, except for the arsenic and

mercury limits , which were based only on data from Polk (since data from Wab ash River failed the LTA test).

For arsenic and mercury, daily concentration values are below both the daily and monthly limits

. For total dissolved solids, there is one (out of four collected in the same month) daily effluent concentration value at Polk above the monthly limit . However, after averaging these four observations, the averag e for the month is below the monthly limit

.

For selenium at Polk, there is one daily effluent concentration value above the daily
limit

. Also, there are two (out of four collected in the same month) daily effluent values above the monthly average limit . A fter averaging these four observations, the average for the month is above the monthly limit

. After thoroughly examining the data, EPA determined that the effluent concentration values for selenium at Polk are relatively higher (i.e., with a higher long

te rm average) than the effluent concentration values at Wabash River

. As discussed above,
since the limits are developed using the data from both plants, it is reasonable to expect that the plant with relatively higher concentrations is more likely to have v alues above the daily and

2 Note that although the Belews Creek selenium data (and other pollutant as w ell) from August

- October 2008 may be influenced by the initial commissioning period for the treatment system, EPA used these data when calculating the proposed effluent limitations for the biological treatment technology option for FGD wastewater

. EPA has used the August

- October 2008 data because although EPA believes that, as a general rule, the initial commissioning period duration will be on the order of 3

- 4 months, and certainly no more than 6 months except in unique circumstances; EPA has not confirmed that the initial commissioning for Belews Creek was of such exceptional duration. Without the information to confirm the commissioning period was still in progress, EPA concluded that the sampling data should be used when calculating effluent limits.

### Page 71 

### monthly limits . Additionally, as discussed above in section 13.8.1, the data for the Polk treatment system indicates that the evaporator (or at a minimum the forced circulation evaporation stage) was operating abnormally and allow ing carryover of pollutants to the condensate effluent stream. Based upon its review of the data, EPA concluded if the plant designs and operat e s its treatment system to achieve the option long

- term average for the model technology, then the plant will be able to comply with the proposed limit . Further, EPA
notes that Polk reuses all treatment gasification wastewater (i.e., condensate) in the gasif ication process and does not discharge any gasification wastewater

. As such, the plant’s treatment objective is to ensure the wastewater is of sufficient quality for reuse in the process rather than to comply with a NPDES permit limit. Thus, EPA concluded that the statistical distributional assumption is appropriate for the effluent data and that the proposed limits are reasonable.

11 .2. Comparison of the Effluent Limit s to Influent Data

In addition to comparing the proposed limits to the data used to develop the limits , EPA also compared the value of the proposed daily limits to the observed influent concentration
values

. This comparison helps evaluate whether the proposed limits are set at a level that
ensures that treatment of th e wastewater would be necessary to meet the limits and that the influent concentrations were generally well

- controlled by the treatment system

. In doing so, EPA confirms that treatment to remove the regulated pollutants will take place

. See Appendix 4
for a detailed listing of the summary statistics for the influent data for each pollutant in each treatment technology option

.

For all treatment technology options for both FGD and gasification wastewater, the minimum, average, and maximum influent concentra tion values were much higher than the long

- term average and proposed limits . Thus, EPA determined that facilities would need to treat the wastewater to ensure compliance with the proposed limits and that the proposed rule would result in removing the regulated pollutants and other pollutants of concern

. Furthermore, in evaluating influent concentrations, EPA found that influent concentrations were generally well

- controlled by the treatment plan t for all plants with the model technology

. In general, the treatment systems adequately treated even the extreme influent values, and the high effluent values did not appear to be the result of high influent discharges.

### Page 72 

## APPENDIX 1: List of All Observati ons that Were Corrected and Excluded Before Calculating the Limits

This appendix contains a listing of all the corrections made to the da ta at Belews Creek and a listing of all observations that were excluded as described in Sections 3.1 and 3.2 of the
d ocument

. It shoul d be noted that the excluded data presented in this appendix are similar to those presented in DCN SE02002. However, the excluded data are presented in this appendix by reasons for exclusion rather than by plant within each technology option as presented in the

DCN SE02002 mentioned above. Further, even though EPA is not using the arsenic and mercury data from Allen and Belews Creek to calculate the limits for biological treatment system (for the
reason described above and in Section 7)

, EPA did perform data corrections and exclusions for the arsenic and mercury data at these two plants.

There are four sections in this appendix

. Sec tion 1 provide s a summary of all the corrections made to the plant self

- monitoring data at Belews Creek due to data entry errors made by Duke Energy in the original data submittal to EPA

. Section 2 contains a summary of data that warranted exclusion because the samples were analyzed using an insufficient ly

sensitive analytical method (i. e., use of EPA Method 245.1 instead of Method 1631E for mercury). Section 3 contains a summary of all dat a that were excluded because the samples were collected during the initial commissioning period for the treatment system

. Section 4 contains a summary of data that were excluded because of : (i) analytical results that were identified as questionable due to quality control issues, (ii) abnormal co nditions or treatment
upsets, and (iii) analytical anomalies.

### Page 73 

### 1. Corrections Made to Plant Self

- Monitoring Data from Belews Creek

As described in Section 3.1

, after thoroughly reviewing the plant self

- monitoring data provided by Duke Energy, EPA found some inconsistencies in the data from Belews Creek

. EPA
detailed the inconsistencies found in the data and requested Duke Energy to address the potential errors. Duke Energy confirmed that the inconsistencies were due to data entry errors

. The following tables provide the corrections that EPA made to the plant self

- monitoring data
for arsenic, mercury, and sele nium , based on the information from Duke Energy

.

The table below list s the corrections made to the detection indicator for data at Belews Creek prior to calculating proposed effluent limits

. The data are arranged by sampling location, pollutant , and sa mpling date.

Table 1. 1 . Summary of the corrected detection indicators for the Belews Creek self

- monitoring data, arranged by sampling location, pollutant, and sampling date.
Sampling Location Pollutant Date Original Indicator 1 Corrected Indicator 1

Bio 1 In (Bioreactor Influent) Mercury 2/6/2008 D ND 2/9/2008 D ND

Bio 2 Eff (Bioreactor Effluent) Arsenic 2/7/2008 ND D 2/8/2008 ND D 2/10/2008 ND D 2/12/2008 ND D 2/13/2008 ND D 2/14/2008 ND D 2/15/2008 ND D 2/16/2008 ND D 2/17/2008 ND D 2/21/2008 ND D

Mercury 2/6/2008 D ND 9/29/2008 ND D 8/11/2010 ND D 9/8/2010 ND D 10/7/2010 ND D

Selenium 3/3/2008 ND D

1 : D = detected and ND = non

- detected



### The table below list s the corrections made to concentration values for data from Belews
Creek prior to performing the statistical analyses

, based on information provided by Duke Energy

.

### Page 74 

### Table 1. 2 . Summary of the data corrections for the Belews Cr eek self

- monitoring data

, arranged by sampling location, pollutant, and sampling date.

Sampling Location Pollutant (unit) Date Original Concentration Value (Indicator) 1 Corrected Concentration Value (Indicator) 1

Bio 1 In (Bioreactor Influent) Mercury (ng /L) 6/9/2010 59.3 (D) 59,300 (D) 7/14/2010 49.9 (D) 49,900 (D) 8/11/2010 47.7 (D) 47,700 (D)

Bio 2 Eff (Bioreactor Effluent) Mercury (ng/L) 5/12/2010 1000 (ND) 136 (D) 5/26/2010 136 (D)

- 2

1 : D = detected; ND = non

- detected

2 : No data available for this date.



### 2

. List of Data Excluded Due to Samples Analyzed Using an Insufficiently

- Sensitive Analytical
Method

As described in Section 3.2.1, i n some cases, Duke Energy analyzed the samples for mercury using EPA Method 1631E, while other samples were analyzed for mercury using EPA
Method 245.1

. The quantitation level for Method 245 .1 is not low enough to detect the concentration of mercury present in the bioreactor influent and effluent samples, and therefore, all mercury results that were analyzed using Metho d 245.1 for bioreactor influent
and effluent samples were excluded

. The table below provides a list of all the excluded data.

It is important to note that there were more data analyzed by Method 245.1 that are
not listed in the table below since those data points were already excluded because they were identified as being collected during either the initial com mission in g period or a period of treatment upset (see Sections 3 and 4 below) , which are presented separately

.

### Page 75 

### Table 1. 3 . Summary of the mercury data excluded from plant self monitoring data due to using an insufficiently

- sensitive analytical method

.

Plant Name Data Source Date Sampling Location Included
in Limits Indicator

1 Concentratio

n (ng/L)

Allen Plant Self

- Monitoring 6/29/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 8/23/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 10/5/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 10/6/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 10/7/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 10/9/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 10/10/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 10/12/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 10/13/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 12/1/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 12/4/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 12/7/2010 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 1/12/2011 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 1/24/2011 Bio Treatment Effluent No ND 1,000
Allen Plant Self

- Monitoring 4/27/2011 Bio Treatment Effluent No ND 1,000

Belews Creek Plant Self

- Monitoring 1/27/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 2/24/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 3/24/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 4/7/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 6/23/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 7/14/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 7/28/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 8/25/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 9/22/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 10/27/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 11/4/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 11/23/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 12/8/2010 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 1/17/2011 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 1/26/2011 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 2/16/2011 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 3/23/2011 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 4/27/2011 Bio Treatment Effluent No ND 1,000
Belews Creek Plant Self

- Monitoring 5/25/2011 Bio Treatment Effluent No ND 1,000

1 : D = detected; ND = non

- detected

### Page 76 

### 3. List of Data Excluded Due to Samples Being Collected During the Initial Commissioning Period for the Treatment System

As described in Section 3.2.2 , EPA generally excludes all data collected during the initial commissioning period for the treatment system

. Since the plant self

- monitoring data for Allen
and Belews Creek included data collected during initia l commissioning period , EPA excluded all
these da ta in calculating the limits

. The commissioning period for the treatment system at each plant was determined as the initial six month period of operation, as follows :

**•** Fo r plant self

- monitoring data from Allen, all data from March 03, 2009 through August 26, 2009 were excluded.

**•** For plant self

- monitoring data from Belews Creek, all data from February 06, 2008 through July 31, 2008 were excluded.

4. List of Data Exc luded D ue to Analytical Results that Identified as Questionable D ue to the Quality Control Issues, Abnormal Conditions or Treatment Upset, or Analytical Anomalies

As described in Section 3.2.3 , EPA exclud ed analytical results that were identified as questionable due to quality control issues, abnormal conditions or treatment upset, or analytical anomalies

. The table below provides a listing of all the data points that were excluded
for these reasons.

Note that additional data from Belews Creek that were identified as questionable due to quality control issues are not listed here since those data were collected during the initial commissioning period and were already excluded for that reason (see Section 3 of this appendix ).

### Page 77 

### Table 1. 4 . Summary of the questionable mercury data excluded due to quality control issues for
the plant self

- monitoring data at Allen and Belews Creek.

Plant Name Data Source Date Sampling Location Included
in Limits Indicator 1 Concentration (ng/L)

Allen Plant Self

- Monitoring 12/29/2009 Bio Treatment Influent No D 710

Allen Plant Self

- Monitoring 12/29/2009 Bio Treatment Effluent No D 11

Allen Plant Self

- Monitoring 1/11/2010 Bio Treatment Influent No D 92

Allen Plant Self

- Monitoring 1/11/2010 Bio Treatment Effluent No D 14.2

Belews Creek Plant Self

- Monitoring 8/4/2008 Bio Treatment Influent No D 4.9

Belews Creek Plant Self

- Monitoring 8/4/2008 Bio Treatment Effluent No D 2.4

Belews Creek Plant Self

- Monitoring 8/11/2008 Bio Treatment Influent No D 4.8

Belews Creek Plant Self

- Monitoring 8/11/2008 Bio Treatment Effluent No D 2.7

Belews Creek Plant Self

- Monitoring 8/18/2008 Bio Treatment Influent No D 24

Belews Creek Plant Self

- Monitoring 8/18/2008 Bio Treatment Effluent No D 5.3

Belews Creek Plant Self

- Monitoring 8/25/2008 Bio Treatment Influent No D 27

Belews Creek Plant Self

- Monitoring 8/25/2008 Bio Treatment Effluent No D 6.4

Belews Creek Plant Self

- Monitoring 9/2/2008 Bio Treatment Influent No D 3.1

Belews Creek Plant Self

- Monitoring 9/2/2008 Bio Treatment Effluent No D 2.1

Belews Creek Plant Self

- Monitoring 9/8/2008 Bio Treatment Influent No D 2.7

Belews Creek Plant Self

- Monitoring 9/8/2008 Bio Treatment Effluent No D 4.1

Belews Creek Plant Self

- Monitoring 9/15/2008 Bio Treatment Influent No D 12

Belews Creek Plant Self

- Monitoring 9/15/2008 Bio Treatment Effluent No ND 1

Belews Creek Plant Self

- Monitoring 9/22/2008 Bio Treatment Influent No D 8.1

Belews Creek Plant Self

- Monitoring 9/22/2008 Bio Treatment Effluent No ND 1

Belews Creek Plant Self

- Monitoring 9/29/2008 Bio Treatment Influent No D 3.4

Belews Creek Plant Self

- Monitoring 9/29/2008 Bio Treatment Effluent No D 3.7

Belews Creek Plant Self

- Monitoring 12/3/2008 FGD Purge No D 16,000

Belews Creek Plant Self

- Monitoring 12/3/2008 Bio Treatment Influent No D 19 2

Belews Creek Plant Self

- Monitoring 12/3/2008 Bio Treatment Effluent No D 3.6

Belews Creek Plant Self

- Monitoring 12/10/2008 FGD Purge No D 44,000

Belews Creek Plant Self

- Monitoring 12/10/2008 Bio Treatment Influent No D 15 2

Belews Creek Plant Self

- Monitoring 12/10/2008 Bio Treatment Effluent No D 2 2

Belews Creek Plant Self

- Monitoring 12/17/2008 Bio Treatment Influent No D 7.6 2

Belews Creek Plant Self

- Monitoring 12/17/2008 Bio Treatment Effluent No D 2.9 2

Belews Creek Plant Self

- Monitoring 12/22/2008 Bio Treatment Influent No D 20 2

Belews Creek Plant Self

- Monitoring 12/22/2008 Bio Treatment Effluent No D 1.4 2

Belews Creek Plant Self

- Monitoring 12/29/2008 Bio Treatment Influent No D 12 2

Belews Creek Plant Self

- Monitoring 12/29/2008 Bio Treatment Effluent No D 2.4 2

Belews Creek Plant Self

- Monitoring 1/7/2009 Bio Treatment Influent No D 5 2

Belews Creek Plant Self

- Monitoring 1/7/2009 Bio Treatment Effluent No D 2.8 2

Belews Creek Plant Self

- Monitoring 1/14/2009 Bio Treatment Influent No D 15 2

Belews Creek Plant Self

- Monitoring 1/14/2009 Bio Treatment Effluent No D 2.3 2

Belews Creek Plant Self

- Monitoring 1/22/2009 Bio Treatment Influent No D 4.7 2

Belews Creek Plant Self

- Monitoring 1/22/2009 Bio Treatment Effluent No D 3.9 2

Belews Creek Plant Self

- Monitoring 1/28/2009 Bio Treatment Influent No D 12 2

Belews Creek Plant Self

- Monitoring 1/28/2009 Bio Treatment Effluent No D 2.6

1 : D = detected; ND = Non

- detected

2 : For these dates, sampling data were analyzed by two laboratories: BrooksRand and Prism. In general, EPA would average the dat a from two available sources in to a single value to use in calculating of limits. However, since the data analyzed by the Prism lab oratory (listed in the table) were identified by Duke Energy as questionable due to quality control issues, EPA has excluded these data and
used only the sampling data from BrooksRand

. Thus, for the given dates, EPA used the data analyzed by BrooksRand to develop the

### Page 78 limits. Note that EPA lacked sufficient laboratory quality control data for these results to make an independent assessment o f whether these mercury results should have been retained and included in the statistical analyses.



### Th e table bel ow provides a list of all the excluded dat a due to abnormal conditions or system upset and analytical anomalies

. Note that the table includes some data that could also be excluded due to an insufficiently

- sensitive analytical method.

Table 1. 5 . Summary of data excluded due to abnormal conditions or treatment upset and analytical anomalies.

Plant

Name Data Source Date Sampling Location Pollutant (unit) Include
d in
Limits Ex clusion

Commen

t Indi

cato

r 1 Concent
ration

Allen Plant Self

- Monitoring 3/8/2010 FGD Purge Arsenic (ug/L) No

System
upset
due to pipe breakage

. Exclude
all data D 553

Allen Plant Self

- Monitoring 3/8/2010 Bio Treatment Influent Arsenic (ug/L) No ND 5

Allen Plant Self

- Monitoring 3/8/2010 Bio Treatment Effluent Arsenic (ug/L) No D 7

Allen Plant Self

- Monitoring 3/22/2010 FGD Purge Arsenic (ug/L) No D 452

Allen Plant Self

- Monitoring 3/22/2010 Bio Treatment Influent Arsenic (ug/L) No ND 5

Allen Plant Self

- Monitoring 3/22/2010 Bio Treatment Effluent Arsenic (ug/L) No D 22.5

Allen Plant Self

- Monitoring 4/5/2010 FGD Purge Arsenic (ug/L) No D 309

Allen Plant Self

- Monitoring 4/5/2010 Bio Treatment Influent Arsenic (ug/L) No ND 5

Allen Plant Self

- Monitoring 4/5/2010 Bio Treatment Effluent Arsenic (ug/L) No D 9

Allen Plant Self

- Monitoring 4/26/2010 FGD Purge Arsenic (ug/L) No D 206

Allen Plant Self

- Monitoring 4/26/2010 Bio Treatment Influent Arsenic (ug/L) No ND 5

Allen Plant Self

- Monitoring 4/26/2010 Bio Treatment Effluent Arsenic (ug/L) No D 6.3

Allen Plant Self

- Monitoring 5/10/2010 FGD Purge Arsenic (ug/L) No D 615

Allen Plant Self

- Monitoring 5/10/2010 Bio Treatment Influent Arsenic (ug/L) No ND 5

Allen Plant Self

- Monitoring 5/10/2010 Bio Treatment Effluent Arsenic (ug/L) No D 63.1

Allen Plant Self

- Monitoring 5/25/2010 FGD Purge Arsenic (ug/L) No D 535

Allen Plant Self

- Monitoring 5/25/2010 Bio Treatment Influent Arsenic (ug/L) No ND 5

Allen Plant Self

- Monitoring 5/25/2010 Bio Treatment Effluent Arsenic (ug/L) No D 63.9

Allen Plant Self

- Monitoring 3/8/2010 FGD Purge Mercury (ng/L) No D 65200

Allen Plant Self

- Monitoring 3/8/2010 Bio Treatment Influent Mercury (ng/L) No D 50.5

Allen Plant Self

- Monitoring 3/8/2010 Bio Treatment Effluent Mercury (ng/L) No D 5.98

Allen Plant Self

- Monitoring 3/22/2010 FGD Purge Mercury (ng/L) No D 51400

Allen Plant Self

- Monitoring 4/5/2010 FGD Purge Mercury (ng/L) No D 59700

Allen Plant Self

- Monitoring 4/5/2010 Bio Treatment Influent Mercury (ng/L) No D 812

Allen Plant Self

- Monitoring 4/5/2010 Bio Treatment Effluent Mercury (ng/L) No D 22.4

Allen Plant Self

- Monitoring 4/26/2010 FGD Purge Mercury (ng/L) No D 40300

Allen Plant Self

- Monitoring 4/26/2010 Bio Treatment Effluent Mercury (ng/L) No ND 1000

Allen Plant Self

- Monitoring 5/10/2010 FGD Purge Mercury (ng/L) No D 41100

Allen Plant Self

- Monitoring 5/10/2010 Bio Treatment Influent Mercury (ng/L) No D 113

Allen Plant Self

- Monitoring 5/10/2010 Bio Treatment Effluent Mercury (ng/L) No D 5.76

Allen Plant Self

- Monitoring 5/25/2010 FGD Purge Mercury (ng/L) No D 65600

Allen Plant Self

- Monitoring 5/25/2010 Bio Treatment Effluent Mercury (ng/L) No ND 1000

Allen Plant Self

- Monitoring 3/8/2010 FGD Purge Selenium (ug/L) No D 1860

Allen Plant Self

- Monitoring 3/8/2010 Bio Treatment Influent Selenium (ug/L) No D 100

Allen Plant Self

- Monitoring 3/8/2010 Bio Treatment Effluent Selenium (ug/L) No D 4.7

Allen Plant Self

- Monitoring 3/22/2010 FGD Purge Selenium (ug/L) No D 1800

Allen Plant Self

- Monitoring 3/22/2010 Bio Treatment Influent Selenium (ug/L) No D 75.8

Allen Plant Self

- Monitoring 3/22/2010 Bio Treatment Effluent Selenium (ug/L) No D 3.1

### Page 79 Plant

Name Data Source Date Sampling Location Pollutant (unit) Include
d in
Limits Ex clusion

Commen

t Indi

cato

r 1 Concent
ration

Allen Plant Self

- Monitoring 4/5/2010 FGD Purge Selenium (ug/L) No D 1450

Allen Plant Self

- Monitoring 4/5/2010 Bio Treatment Influent Selenium (ug/L) No D 75.3

Allen Plant Self

- Monitoring 4/5/2010 Bio Treatment Effluent Selenium (ug/L) No D 2.7

Allen Plant Self

- Monitoring 4/26/2010 FGD Purge Selenium (ug/L) No D 1690

Allen Plant Self

- Monitoring 4/26/2010 Bio Treatment Influent Selenium (ug/L) No D 353

Allen Plant Self

- Monitoring 4/26/2010 Bio Treatment Effluent Selenium (ug/L) No D 3.2

Allen Plant Self

- Monitoring 5/10/2010 FGD Purge Selenium (ug/L) No D 1400

Allen Plant Self

- Monitoring 5/10/2010 Bio Treatment Influent Selenium (ug/L) No D 86.9

Allen Plant Self

- Monitoring 5/10/2010 Bio Treatment Effluent Selenium (ug/L) No D 2.6

Allen Plant Self

- Monitoring 5/25/2010 FGD Purge Selenium (ug/L) No D 5350

Allen Plant Self

- Monitoring 5/25/2010 Bio Treatment Influent Selenium (ug/L) No D 96.2

Allen Plant Self

- Monitoring 5/25/2010 Bio Treatment Effluent Selenium (ug/L) No D 3.5

Hatfield’ s Ferry CWA 308 Sampling 10/5/2010 Chem Prep. Effluent Mercury (ng/L) No Abnormal
condition

or

treatmen t upset D 978

Belews
Creek EPA Sampling 6/9/2010 Bio Treatment Effluent Dup Mercury (ng/L) No Analytical
anomalie

s D 6440

Belews
Creek Plant Self

- Monitoring 7/14/2010 Bio Treatment Effluent Selenium (ug/L) No D 299

1 : D = detected; ND = non

- detected

.

### Page 80 

## APPENDIX 2: Plots of Plant Self

- monitoring Data with Smoothed Curves t o Aid in Determining Initial Commissioning Period of Treatment System

As explained in Section 3.2.2, EPA excluded some data collected during the initial commissioning p eriod of the tre atment system from the plant self

- monitoring data from Allen
and Belews Creek

. The initial commissioning period was determined from an engineering perspective based on extensive experience evaluating treatment systems at power plants and other industry sectors and knowledge of the physical, chemical, and biological treatment processes employed and by looking at the longitudinal plots of all the data

. In additio n to the longitudinal plots of the data, smooth curves obtained by LOWESS (Cleveland, 1979 and 1981) superimposed on the individual data plots were also examined to help determine when the treatment system appeared to stabilize

. In examining the longitudin al plots, EPA looked at two types of plots: plots of all the available plant self

- monitoring data and plots of data after the
exclusions for plant self

- monitoring data described in Sections 3.2.1 and 3.2.3

. The conclusion s from both of these approaches wer e consistent

. The initial six months of operation was determined to represent a reasonable estimate of the commissioning period for the treatment
systems

.

This appendix contains the longitudinal plots for arsenic, mercury, and selenium that engineers use d as aid s in determining the commissioning period for Allen and Belews Creek

. Four plots are given for each pollutant in this appendix

. The first plot shows all the available data points for the plant self

- monitoring (before all the exclusions for plant self

- monitoring data
described in Section s 3.2.1 and 3.2.3 ) for Allen and Belews Creek. The second plot is based on
all available data ( as in the first plot) with smooth curves ( obtained by LOWESS ) superimposed on the individual data. The third p lot is a plot of the data after all necessary exclusions for plant
self

- monitoring ( as described in Sections 3.2.1 and 3.2.3)

. The fourth plot is the plot of the data after all necessary exclusions ( as in the third plot) with smooth curves ( obtained by LOW ESS ) superimposed on the individual data points.

For each plot, the plot on the left shows concentrations for Allen from March 3, 2009 to May 23, 2011. The plot on the right shows concentrations for Belews Creek from February 6, 2008 to May 25, 2011. Wit hin each plot, the plots on the upper row shows the concentrations collected at all three sampling locations, while the plots on the bottom row show the concentrations only at the bioreactor influent and bioreactor effluent. The red line on the plot

repres ents the end of the commissioning period.

### Page 81 

### Figure 2. 1 . Plot of all self

- monitoring data for arsenic (ug/L) for Allen and Belews Creek.

Figure 2. 2 . Smoothed plot (using LOWESS) of all self

- monitoring data for arsenic (ug/L) for Allen
and Belews Creek.010002000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreactor Eff.010002000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* *

* * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* *

* * * * * * * Bioreactor Inf.
Bioreator Eff.010002000 Allen

DateArsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Allen

DateArsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 Bioreactor Inf.
Bioreactor Eff.010002000 Belews Creek

DateArsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Belews Creek

DateArsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 Bioreactor Inf.
Bioreactor Eff.

### Page 82 

### Figure 2. 3

. Plot of self

- monitoring data for arsenic (ug/L) for Allen and Belews Creek after
exclusions described in Sections 3.2.1 and 3.2.3

.

Figure 2. 4

. Smoo thed plot (using LOWESS) of self

- monitoring data for arsenic (u g/L) for Allen
and Belews Creek after exclusions described in Sections 3.2.1 and 3.2.3

.010002000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreactor Eff.010002000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Arsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* *

* * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* *

* * * * * * * Bioreactor Inf.
Bioreator Eff.010002000 Allen

DateArsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Allen

DateArsenic (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 Bioreactor Inf.
Bioreactor Eff.010002000 Belews Creek

DateArsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.050150250 Belews Creek

DateArsenic (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 Bioreactor Inf.
Bioreactor Eff.

### Page 83 

### Figure 2. 5

. Plot of all self

- monitorin g data for mercury (ng/L) for Allen and Belews Creek.

Figure 2. 6

. Smoothed plo t (usi ng LOWESS) of all self

- monitoring data for mercury (ng/L) for
Allen and Belews Creek.0e+003e+056e+05 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Apr 10 Jul 10 Oct 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Bioreactor Inf.
Bioreactor Eff.0e+003e+056e+05 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Feb 08 Jun 08 Dec 08 Jun 09 Nov 09 Mar 10 Aug 10 Jan 11 * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreator Eff.0e+003e+056e+05 Allen

DateMercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Allen

DateMercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Apr 10 Jul 10 Oct 10 Jan 11 Apr 11 Bioreactor Inf.
Bioreactor Eff.0e+003e+056e+05 Belews Creek

DateMercury (ng/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Belews Creek

DateMercury (ng/L)

Feb 08 Jun 08 Dec 08 Jun 09 Nov 09 Mar 10 Aug 10 Jan 11 Bioreactor Inf.
Bioreactor Eff.

### Page 84 

### Figure 2. 7

. Plot of self

- monitoring data for mercury (ng/L) for Allen and Belews Creek after
exclusions described in Sections 3.2.1 and 3.2.3.

Figure 2. 8

. Smoothed plot (using LOWESS) of all self

- monitoring data for mercury (n g/L) for
Allen and Belews Creek after exclusions described in Sections 3.2.1 and 3.2.3.0e+003e+056e+05 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Bioreactor Inf.
Bioreactor Eff.0e+003e+056e+05 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Mercury (ng/L)

Feb 08 Jun 08 Dec 08 Jun 09 Nov 09 Mar 10 Aug 10 Jan 11 * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreator Eff.0e+003e+056e+05 Allen

DateMercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Allen

DateMercury (ng/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 Bioreactor Inf.
Bioreactor Eff.0e+003e+056e+05 Belews Creek

DateMercury (ng/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.02000050000 Belews Creek

DateMercury (ng/L)

Feb 08 Jun 08 Dec 08 Jun 09 Nov 09 Mar 10 Aug 10 Jan 11 Bioreactor Inf.
Bioreactor Eff.

### Page 85 

### Figure 2. 9

. Plot of all self

- monitoring data for selenium (ug/L) for Allen and Belews Creek.

Figure 2. 10

. Smoothed plo t (using LOWESS) of all self

- monitoring data for selenium (ug/L) for
Allen and Belews Creek.01000020000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreactor Eff.01000020000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreator Eff.01000020000 Allen

DateSelenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Allen

DateSelenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Mar 10 Jun 10 Oct 10 Jan 11 Apr 11 Bioreactor Inf.
Bioreactor Eff.01000020000 Belews Creek

DateSelenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Belews Creek

DateSelenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 Bioreactor Inf.
Bioreactor Eff.

### Page 86 

### Figure 2. 11

. Plot of self

- monitoring data for selenium (ug/L) for Allen and Belews Creek after
exclusions described in Sections 3.2.1 and 3.2.3

.

Figure 2. 12

. Smoothed plot (usin g LOWESS) of s elf

- monitoring data for selenium (ug/L) for Allen
and Belews Creek after exclusions described in Sections 3.2.1 and 3.2.3.

References

Cleveland, W. S. (1979) Robust locally weighted regression and smoothing scatterplots. J. Amer. Statist.

Assoc. 74 , 829

– 836.

Cleveland, W. S. (1981) LOWESS: A program for smoothing scatterplots by robust locally weighted
regression. The American Statistician

, 35 , 54.01000020000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Allen

Date (Vertical line at 8/26/09, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreactor Eff.01000020000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Belews Creek

Date (Vertical line at 7/31/08, end of commissio
Detected: o Non-Detected: *Selenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Bioreactor Inf.
Bioreator Eff.01000020000 Allen

DateSelenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Allen

DateSelenium (ug/L)

Mar 09 Jun 09 Sep 09 Dec 09 Jun 10 Sep 10 Jan 11 Apr 11 Bioreactor Inf.
Bioreactor Eff.01000020000 Belews Creek

DateSelenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 FGD Purge
Bioreactor Inf.
Bioreactor Eff.0100020003000 Belews Creek

DateSelenium (ug/L)

Feb 08 Jun 08 Nov 08 Apr 09 Sep 09 Feb 10 Jul 10 Nov 10 Apr 11 Bioreactor Inf.
Bioreactor Eff.

### Page 87 

## APPENDIX 3: Data Editing Criteria Results

This appendix contains a summary of the results of the data editing criteria on a pollutant

- by

- pollutant basis to select a dataset at each plant to be used for calculating the effluent limits for each technology option (described in Section 4 of the document)

. These criteria are referred to as the long

- term average test (or LTA test)

. EPA established the LTA test
to ensure that the pollutants for which limits are being proposed were present in the influent at
sufficient concentrat ions to evaluate treatment effectiveness at the plant

. The data editing procedure is specified as fo llows: first, the influent had to pass a basic requirement that 50% of
the influent me asurements for the pollutant have to be detected at any concentration

. If the dataset for a pollutant at a plant passed the basic requirement, it then had to pass one of the following two criteria to pass the LTA test:

Criterion 1. At least 50% of the influent measureme nts in a dataset at a plant are detected at levels equal to or greater than 10 times the baseline value ( shown in

Section 3.3 ).

Criterion 2. At least 50% of the influent measurem ents in a dataset at a plant ar e detected at any concentration and the influent arithmetic average equal to or greater than 10 times the baseline value ( shown in Section 3.3 ).

If the dataset at a plant failed the basic requirement, then EPA automatically set both
Criteria 1 and 2 to “fail”

. If the dataset for a plant failed the basic requirement, or passed the basic requirement but failed both criteria, EPA would exclude the plant’s effluent data for that pollutant when calculating the limits

. Through the application of the LTA test, EPA ensures that
the limits result from treatment of the wastewater and not si mply the absence or substantial dilution of that pollutant in the waste stream.

### Page 88 

### The table below shows how each pollutant at each plant fared with respect to the basic requirement and the two criteria of the LTA test

. The b ullets below provide a brief description for the important columns in the table:

**•** Column “N” presents the total numb er of influent observations (detected and non

detected combined)

**•** Column “Percent Detected for Influent (%)” shows the percent of influent observations
that are detected

.

**•** Column “Basic Requirement” contains an indicator of whether the dataset passed (or failed) the basic requirem ent in the data editing criteria.

**•** Column “Baseline Value” shows the baseline value for each pollutant.

**•** Column “% Influent values ≥10*baseline val ue” contains the percent of influent
observations that are at least 10 times the baseline values.

**•** Column “Criterion 1” contains an indicator of whether the dataset passed (or failed)
criterion 1 of the LTA test.

**•** Column “Mean Influent” shows the mean of the influent concentrations.

**•** Column “Criterion 2” contains an indicator of whether the dataset passed (or failed)
criterion 2 of the LTA test.

The influent sampling location at each plant is given in the bul lets below:

**•** FGD Purge: Allen, Belews Creek, Hatfield’s Ferry, Keystone, Miami Fort, and Brindisi.

**•** Vapor Compression Evaporator Influent: Polk and Wabash River.

As shown in the table, the data for each pollutant at each of the plants all passed the LTA test, except for arsenic and mercury at Wa bash River

. Since the data for these pollutants failed the LTA test, EPA excluded the Wabash River data for these pollutants in developing the
limit s for gasification wastewater.

### Page 89 

### Table 3. 1

. Summary of the results for data editing procedure performed to select a dataset for pollutant at each plant in calculating the limits

.

Plant

Name Pollutant (unit) N 1 Percent
Detected for Influent (%) Basic Requirem

ent 2 Baseli

ne Value % I nfluent
values ≥ 10*baseline (%) Criteri

on 1 Mean
Influent Criterio

n 2

Allen Arsenic (ug/L) 63 100 Passed 2 100 Passed 233.3 Passed

Allen Mercury (ng/L) 62 100 Passed 0.5 100 Passed 52,219.4 Passed

Allen Nitrate Nitrite as N (mg/L) 8 100 Passed 0.05 100 Passed 32.0 Passed

Allen Selenium (ug/L) 63 100 Passed 5 100 Passed 1,685.2 Passed

Belews
Creek Arsenic (ug/L) 70 100 Passed 2 100 Passed 411.4 Passed

Belews
Creek Mercury (ng/L) 73 100 Passed 0.5 100 Passed 194,417.8 Passed

Belews
Creek Nitrate Nitrite as N (mg/L) 8 100 Passed 0.05 100 Passed 16.6 Passed

Belews
Creek Selenium (ug/L) 76 100 Passed 5 100 Passed 6,797.3 Passed

Hatfield ’ s Ferry Arsenic (ug/L) 8 100 Passed 2 100 Passed 1,796.3 Passed

Hatfield ’ s Ferry Mercury (ng/L) 8 100 Passed 0.5 100 Passed 465,125.0 Passed

Keystone Arsenic (ug/L) 8 100 Passed 2 100 Passed 1,815.0 Passed

Keystone Mercury (ng/L) 8 100 Passed 0.5 100 Passed 404,225.0 Passed

Miami Fort Arsenic (ug/L) 8 100 Passed 2 100 Passed 727.3 Passed

Miami Fort Mercury (ng/L) 8 100 Passed 0.5 100 Passed 235,375.0 Passed

Brindisi Arsenic (ug/L) 2 100 Passed 2 100 Passed 54.0 Passed

Brindisi Mercury (ng/L) 2 100 Passed 0.5 100 Passed 240,00.0 Passed

Brindisi Selenium (ug/L) 2 100 Passed 5 100 Passed 255.0 Passed

Brindisi TDS (mg/L) 2 100 Passed 10 100 Passed 14,000.0 Passed

Polk Arsenic (ug/L) 4 100 Passed 2 100 Passed 280.0 Passed

Polk Mercury (ng/L) 4 100 Passed 0.5 100 Passed 70.4 Passed

Polk Selenium (ug/L) 4 100 Passed 5 100 Passed 1,277.5 Passed

Polk TDS (mg/L) 4 100 Passed 10 100 Passed 4,575.0 Passed

Wabash

River Arsenic (ug/L) 4 50 Passed 2 0 Failed 4.5 Failed

Wabash

River Mercury (ng/L) 4 0 Failed 0.5 75 Failed 8.7 Failed

Wabash

River Selenium (ug/L) 4 100 Passed 5 100 Passed 920.0 Passed

Wabash

River TDS (mg/L) 4 100 Passed 10 100 Passed 4,225.0 Passed

1 : Total number of observations (detected and non

- detected combined).

2 : if a dataset fails the basic requirement, EPA automatically set both Criteria 1 and 2 to Failed.

### Page 90 

## APPENDIX 4: Summary of the Results for the Engi neering Review of the Limit s

As describ ed in Section 11 , to evaluate whether the proposed limits are reasonable , EPA performed an engineering review to verify that the limits are reasonable based upon the design and expected operation of the control technologies

. EPA performed two types of comparisons
for this evaluation

. First, EPA compared the limits to the effluent data used to develop the
limits

. Second, EPA compared the limits to the influent data

. This appendix contains a listing of the daily effluent concentration values that are above the maximum daily and monthly average limits for each pollutant in each technology option

. In addition, the list of effluent daily values collected in the same month as any daily value that exceeded the monthly limitation are also given in this appendix.

There are two sections in this appendix. Section 1 contains the results of the comparisons between the limits and effluent data used to develop the limits for each technology option

. Section 2 contains the results of the comparisons between th e limits and
influent da ta for each technology option.

### Page 91 

### 1. Results of the Comparison of the Limits to Effluent Data Used as the Basis for the Limit s

Tables below provide the listing of the daily effluent values that are above the daily
limits

. In additio n, a list of the daily values that are above the average monthly limits ( and all
other values in the same month in which any daily value is above the monthly limit ) is also provided for each treatment technology option for FGD and gasification wastewaters.

Chemical Precipitation Treatment Technology Option for FGD Wastewater

The table below provides a list of all the daily data that are above the maximum d aily limits for each pollutant.

Table 4. 1 . Listi ng of all daily values that are above the daily limits for chemical precipitation

treatment for FGD wastewater

.

Plant Name Data Source Pollutant (unit) Date Daily
Limit 1 Concentr
ation Indica

tor 2 Above daily limit Hatfield’s Ferry CWA 308 Sampling Arsenic (ug/L) 1/12/2011 8 11 D Yes Hatfield’s Ferry CWA 308 Sampling Arsenic (ug/L) 2/9/2011 8 10 D Yes

Miami Fort CWA 308 Sampling Mercury (ng/L) 9/28/2010 242 256 D Yes

Miami Fort CWA 308 Sampling Mercury (ng/L) 11/2/2010 242 295 D Yes

1 : Daily limit set for each pollutant.

2 : D = detected and ND = non

- detected



### The table below provides a list of all the daily values that are above the monthly limits
for each pollutant

. Also included in the table are all other daily values collected in the same month as any daily value that exceeded the monthly limitation. For example, for arsenic at Hatfield’s Ferry, there are two daily observations in December, 2010 that are above the daily
limits and two other daily observations collected the same month that are not above the daily
limits.

### Page 92 

### Table 4. 2 . For chemical precipitation treatment for FGD wastewater , a listing of all the daily
values that are above the monthly limits, along with any other daily values collected in the
same month.

Plant Name Data Source Pollutant (unit) Date Monthly
Limit 1 Concentr
ation Indic

ator 2 Above monthly

limit Above daily
limit
Hatfield ’ s Ferry EPA Sampling Arsenic (ug/L) 12/7/2010 6 5.4 D No No
Hatfield ’ s Ferry EPA Sampling Arsenic (ug/L) 12/8/2010 6 4.6 D No No
Hatfield ’ s Ferry EPA Sampling Arsenic (ug/L) 12/9/2010 6 6.4 D Yes No
Hatfield ’ s Ferry EPA Sampling Arsenic (ug/L) 12/10/2010 6 7.6 D Yes No
Hatfield ’ s Ferry CWA 308 Sampling Arsenic (ug/L) 1/12/2011 6 11 D Yes Yes
Hatfield ’ s Ferry CWA 308 Sampling Arsenic (ug/L) 2/9/2011 6 10 D Yes Yes
Hatfield ’ s Ferry CWA 308 Sampling Mercury (ng/L) 11/10/2010 119 228 D Yes No

Miami Fort EPA Sampling Mercury (ng/L) 7/13/2010 119 101 D No No

Miami Fort EPA Sampling Mercury (ng/L) 7/14/2010 119 104.9 D No No

Miami Fort EPA Sampling Mercury (ng/L) 7/15/2010 119 148 D Yes No

Miami Fort EPA Sampling Mercury (ng/L) 7/16/2010 119 165 D Yes No

Miami Fort CWA 308 Sampling Mercury (ng/L) 9/28/2010 119 256 D Yes Yes

Miami Fort CWA 308 Sampling Mercury (ng/L) 11/2/2010 119 295 D Yes Yes

Miami Fort CWA 308 Sampling Mercury (ng/L) 12/7/2010 119 144 D Yes No

Miami Fort CWA 308 Sampling Mercury (ng/L) 1/14/2011 119 127 D Yes No

1 : Monthly limit set for each pollutant.

2 : D = detected and ND = non

- detected.



### Chemical Precipitation Followed by Biological Treatment Technology Option for FGD

Wastewater

The table below provides a list of all daily observations at Allen or Belews Creek that are above the daily limits for each pollutant (see discussion in Section 1 1 of the document for a detailed discussion of the comparison).

Table 4. 3 . Listing of all daily values that are above the daily limits for the biological treatment technology option for FGD wastewater.

Plant Name Data S ource Pollutant (unit) Date Daily
Limit 1 Concentra
tion Indicat

or 2 A bove daily
limit

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 8/18/2008 16 18.9 D Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 8/25/2008 16 19.6 D Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/8/2008 16 21.3 D Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/15/2008 16 22.4 D Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/29/2008 16 17.9 D Yes

Belews Creek EPA Sampling Selenium (ug/L) 6/9/2010 16 16.6 D Yes

Belews Creek EPA Sampling Selenium (ug/L) 6/11/2010 16 25 D Yes

Belews Creek CWA 308 Sampling Selenium (ug/L) 12/8/2010 16 29.35 D Yes

1 : Daily limit set for each pollutant.

2 : D = detected and ND = non

- detected.

### Page 93 

### The table below provides a list of all the daily values that are above the monthly limits for each pollutant , along with other daily values collected in the same month.

Table 4. 4 . For biological treatment for FGD wastewater , a listing of all the daily values that are above the monthly limits, along with any other daily values collected in the same month

.

Plant Name Data Source Pollutant (unit) Date Monthl y Limit 1 Concen
tration Indica

tor 2 Above
monthl y limit Above daily
limit

Allen Plant Self

- Monitoring Selenium (ug/L) 5/9/2011 10 5 ND No No

Allen Plant Self

- Monitoring Selenium (ug/L) 5/23/2011 10 11.7 D Yes No

Belews Creek CWA 308 Sampling Nitrate

- nitrite as

N (mg/L) 11/3/2010 0.13 0.15 D Yes No

Belews Creek CWA 308 Sampling Nitrate

- nitrite as

N (mg/L) 1/17/2011 0.13 0.14 D Yes No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 8/4/2008 10 10 ND No No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 8/11/2008 10 15 D Yes No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 8/18/2008 10 18.9 D Yes Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 8/25/2008 10 19.6 D Yes Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/2/2008 10 12.5 D Yes No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/8/2008 10 21.3 D Yes Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/15/2008 10 22.4 D Yes Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/22/2008 10 10.1 D Yes No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 9/29/2008 10 17.9 D Yes Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 10/6/2008 10 15.6 D Yes No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 10/12/2008 10 10 ND No No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 10/20/2008 10 10.7 D Yes No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 10/26/2008 10 10 ND No No

Belews Creek EPA Sampling Selenium (ug/L) 6/8/2010 10 7.3 D No No

Belews Creek EPA Sampling Selenium (ug/L) 6/9/2010 10 16.6 D Yes Yes

Belews Creek EPA Sampling Selenium (ug/L) 6/10/2010 10 5.1 D No No

Belews Creek EPA Sampling Selenium (ug/L) 6/11/2010 10 25 D Yes Yes

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 6/23/2010 10 5 ND No No

Belews Creek Plant Self

- Monitoring Selenium (ug/L) 7/28/2010 10 12 D Yes No

Belews Creek CWA 308 Sampling Selenium (ug/L) 12/8/2010 10 29.35 D Yes Yes

1 : Monthly limit for each pollutant.

2 : D = detected and ND = non

- detected.



### Chemical Precipitation Followed By Vapor

- Compression Evaporation Treatment Technology Option for FGD Wastewater

All concentration values at both brine concentrator distillate and crystallizer condensate are below the daily and monthly limits.

### Page 94 

### Vapor

- Compression Evaporation Treatment Technology Option for Gasification Wastewater

The table below provides a list of all the daily data that are above the maximum d aily limits for each pollutant.

Table 4. 5

. Listing of all daily values that are above the daily limits for vapor

- compression evaporation t reatment for gasification wastewater.

Plant Name Data Source Pollutant (unit) Date Daily Limit 1 Concentra
tion Indicat

or 2 Above daily limit

Polk EPA Sampling Selenium (ug/L) 10/26/2011 453 470 D Yes

1 : Daily limit set for each pollutant.

2 : D = detected and ND = non

- detected.



### The table below provides a list of all the daily values that are above the monthly limits for each pollutant , along with other daily values collected in the same month

.

Table 4. 6

. For vapor

- compression evaporation treatment for gasification wastewater, a listing of all the daily values that are above the monthly limits, along with any other daily values
collected in the same month

.

Plant

Name Data Source Pollutant (unit) Date Monthly
Limit 1 Concentr
ation Indicato

r 2 Above
Monthl

y limit Above daily
limit

Polk EPA Sampling Selenium (ug/L) 10/18 /2011 227 180 D No No

Polk EPA Sampling Selenium (ug/L) 10/19 /2011 227 140 D No No

Polk EPA Sampling Selenium (ug/L) 10/26 /2011 227 470 D Yes Yes

Polk EPA Sampling Selenium (ug/L) 10/27 /2011 227 320 D Yes No

Polk EPA Sampling TDS (m g/L) 10/18/2011 22 23 D Yes No

Polk EPA Sampling TDS (m g/L) 10/19 /2011 22 12 D No No

Polk EPA Sampling TDS (m g/L) 10/26 /2011 22 11 D No No

Polk EPA Sampling TDS (m g/L) 10/27 /2011 22 19 D No No

1 : Daily limit set for each pollutant.

2 : D = detected and ND = non

- detected.



### 2. Comparison of the Effluent Limits to Influent Data

In addition to comparing the proposed limits to the effluent data used to develop the limits, EPA also compared the proposed limits to the influent data

. Sections below provide the influent summary statistics for all plants f r om which the data were used as the bas is for calculating the limits.

### Page 95 

### Chemical Precipitation Treatment Technology Option for FGD Wastewater

Table below provides the summary statistics for influent (FGD Purge) for arsenic and mercury at Hatfield’s Ferry, Keystone, and Miami Fort

. Also provided in the table are the proposed daily maximum limits for each pollutant.

Table 4. 7 . Summary statistics for the influent (FGD Purge) concentrations for plants from which the data were used as the basis for calculating the limits for chemical precipitation treatment technology option for FGD wastewater

. Pollutant (proposed daily limits ) Plant Name Summary Statistics for influent by Pollutant and Plant Name

N Minimum Median Mean Maximum

Arsenic (Daily Limit = 8 ug/L) Hatfield’s Ferry 8 300.0 1,575.0 1,796.3 4,610.0
Keystone 8 450.0 2,035.0 1,815.0 3,080.0

Miami Fort 8 320.0 682.5 727.3 1,310.0

Mercury (Daily Limit = 242 ng/L) Hatfield’s Ferry 8 184,000.0 467,000.0 465,125.0 789,000.0
Keystone 8 18,800.0 514,000.0 404,225.0 622,000.0

Miami Fort 8 44,000.0 227,500.0 235,375.0 384,000.0



### Chemical Precipitation Followed By Biological Treatment Technology Option for FGD

Wastewater

The table below presents the influent (FGD Purge) summary statistics for all plants f r om which the data w ere used as the basis for calculating the limits

. Also provided in the table are the proposed daily limits for each pollutant

. It should be noted that even though EPA transferred the limits for arsenic and mercury from chemical precipitation to the biological treatment technology option for FGD wastewater, the comparison between the influent values
for Allen and Belews Creek and t he limits for the chemical precipitation technology option are still provided below

.

Table 4. 8 . Summary statistics for the influent (FGD Purge) concentrations for plants from which the data were used as the basis for calculating the limits for biological treatment technology option for FGD wastewater

. Pollutant (proposed daily limits ) Plant Name Summary Statistics for influent by Pollutant and Plant Name

N Minimum Median Mean Maximum

Arsenic 1
(Daily Limit = 8 ug/L ) Allen 63 105.0 208.0 233.3 619.0

Belews Creek 70 92.0 278.0 411.4 2,820.0

Mercury 1
(Daily Limit = 242 ng/L) Allen 62 18,500.0 49,950.0 52,219.4 120,000.0

Belews Creek 73 1,000.0 185,000.0 194,417.8 697,000.0

Nitrate

- nitrite as N (Daily Limit = 0.17 mg/L) Allen 8 14.0 29.5 32.0 51.0

Belews Creek 8 14.0 15.5 16.6 21.0

Selenium (Daily Limit = 16 ug/L) Allen 63 849.0 1,660.0 1,685.2 3,260.0

Belews Creek 76 1,660.0 6,625.0 6,797.3 26,200.0

1 : The limits were transferred from chemical precipitation for FGD wastewater.

### Page 96 

### Chemical Precipitation Followed By Vapor

- Compression Evaporation Treatment Technology Option for FGD Wastewater

The table below presents the influent (FGD Purge) summary statistics for all plants f r om which the data w ere used as the basis for calculating the limits

. Also provided in the table are the proposed daily limits for each pollutant.

Table 4. 9

. Summary statistics for the influent (FGD Purge) concentrations for plants from which
the data were used a s the basis for calculating the limits for vapor

- compression evaporation treatment technology option for FGD wastewater

. Pollutant (proposed daily limits ) Plant Name Summary Statistics for influent by Pollutant and Plant Name

N Minimum Median Mean Maximum

Arsenic (Daily Limit = 4 ug/L, based on the
detection limit) Brindisi 2 53.0 54.0 54.0 55.0

Mercury (Daily Limit = 39 ng/L ) Brindisi 2 21,100.0 24,000.0 24,000.0 26,900.0

Selenium (Daily Limit = 5 ug/L, based on the
detection limit) Brindisi 2 220.0 255.0 255.0 290.0

Total Dissolved Solids (Daily Limit = 50 mg/L) Brindisi 2 13,000.0 14,000.0 14,000.0 15,000.0



### Vapor

- Compression Evaporation Treatment Technology Option for Gasification Wastewater

The table below pres ents the influent summary statistics for all pollutant s at Polk and
Wabash River

. Also provided in the table is the p roposed daily limit for each pollutant

. As mentioned above, the data for arsenic and mercury at Wabash River failed the data editing criteria, thus the data for the se two pollutants at Wabash River were excluded from developing the limits for this technology option

. However, for completeness, the summary statistics for arsenic and mercury are provided in the table below

.

### Page 97 

### Table 4. 10 . Summ ary statistics for the influent (vapor compression evaporator influent) concentrations from plants for which the data were used as the basis for calculating the limits for vapor

- compression evaporation treatment technology option for gasification wastewate r.
Pollutant (p roposed daily limits ) Plant Name Summary Statistics for influent by Pollutant and Plant Name

N Minimum Median Mean Maximum

Arsenic (Daily Limit = 4 ug/L , based on

detection limit ) Polk 4 220.0 280.0 280.0 340.0

Wabash River 4 4.0 4.5 4.5 5.0

Mercury (Daily Limit = 1.76 ng/L) Polk 4 17.0 85.9 70.4 92.7

Wabash River 4 5.0 9.9 8.7 9.9

Selenium (Daily Limit = 453 ug/L) Polk 4 720.0 1,295.0 1,277.5 1,800.0

Wabash River 4 800.0 890.0 920.0 1,100.0

Total Dissolved Solids (Daily Limit = 38 mg/L ) Polk 4 4,500.0 4,600.0 4,575.0 4,600.0

Wabash River 4 3,600.0 4,400.0 4,225.0 4,500.0