--------------------------------------------------------------------------------
MEMORANDUM


TO:	Steam Electric Rulemaking Record

FROM:	Daisy Wang, ERG
	TJ Finseth, ERG

DATE:	April 19, 2013

SUBJECT:	Pollutants of Concern Methodology Memorandum


ERG is providing technical support to the U.S. Environmental Protection Agency's Office of Water, Engineering and Analysis Division (EAD) for development of effluent limitations guidelines and standards (ELGs) for the Steam Electric Power Generating Industry. EPA, with the support of ERG, evaluated characterization data from each of the wastestreams targeted by the proposed ELGs. When developing the effluent limitations included in the proposed ELGs, EPA first evaluates which pollutants are present in the wastewater and whether those pollutants are present at treatable levels. The pollutants that meet these criteria are identified as pollutants of concern (POC) for that specific wastestream. EPA then evaluates which of the POCs to set effluent limits based on factors described in Section 11 of the Technical Development Document for the Proposed Effluent Guidelines and Standards for the Steam Electric Power Generating Point Source Category (Technical Development Document). This memorandum describes the approach used to identify POCs for each wastestream targeted in this rulemaking.
Introduction
Constituents present in combustion residual wastewater are primarily derived from the parent carbon feedstock (e.g., coal, petroleum coke). A number of these constituents have the potential to cause environmental harm depending on the mass pollutant loadings, wastewater concentration, and how organisms are exposed to them in the environment. Constituents that EPA identified as POCs were used as the starting point to identify which pollutants to set effluent limitations. 
Data Used For POC Analysis
EPA conducted a field sampling program as part of the detailed study and rulemaking efforts for the Steam Electric ELGs to characterize the wastewater generated by the industry. The analytes selected for analysis reflect EPA's current understanding of power plant wastewaters, including contributions from scrubber sorbents, treatment chemicals, and other sources. As part of the sampling program, EPA collected analytical data for FGD wastewater, ash transport wastewater, leachate from landfills and impoundments containing combustion residuals, and integrated gasification combined cycle (IGCC) wastewater.
EPA used the following data to identify POCs for each of the different wastestreams:
FGD wastewater: EPA sampled untreated FGD wastewater from seven steam electric power plants operating FGD wastewater treatment systems as part of the rulemaking. EPA reviewed the untreated FGD wastewater data for these seven plants (total of seven sampling points and 28 samples) to identify the FGD wastewater POCs.
Ash transport wastewater: EPA sampled untreated fly ash transport water at one plant during the steam electric detailed study. EPA reviewed the untreated fly ash transport water data from this plant (one sampling point and one sample) to identify the fly ash and bottom ash transport water POCs.
Leachate from impoundments and landfills containing combustion residuals: EPA required a subset of plants to sample their impoundment and landfill leachate as part of the Questionnaire for the Steam Electric Power Generating Effluent Guidelines (Steam Electric Survey). EPA reviewed the untreated leachate data collected from the survey responses to identify POCs for impoundment and landfill leachate.
Gasification wastewater: EPA sampled wastewater streams at two plants operating IGCC generating units as part of the Clean Water Action (CWA) 308 sampling program. EPA reviewed the untreated wastewater data from these two steam electric power plants (total of five sampling points and 20 samples) to identify POCs for IGCC wastewater.
Flue gas mercury control (FGMC) wastewater: EPA does not have any sampling data specific to FGMC wastewater. Based on responses to the Steam Electric Survey, EPA determined that the majority of plants generating FGMC wastewater are collecting the FGMC waste with the bulk of the fly ash removed from the flue gas, therefore EPA assumed that POCs associated with FGMC wastewater will be the same as those for fly ash transport water.
Nonchemical metal cleaning wastes: EPA collected characterization data associated with chemical and nonchemical metal cleaning wastes as part of the 1974 rulemaking.  EPA used data from this previous rulemaking to identify POCs for nonchemical metal cleaning wastes.

For more information on the analytes evaluated in the EPA sampling program, refer to Section 3 of the Technical Development Document.
POC Analysis Methodology
EPA used the analytical data from the various sampling episodes (and other data sources) to identify the POCs considered for this rulemaking. From the list of analytes sampled, EPA eliminated from consideration any pollutants that were never detected in the untreated wastewater samples, EPA then reviewed its data from untreated wastewater samples from individual wastestreams to identify pollutants detected at greater than or equal to 10 times the baseline value in at least 10 percent of all untreated process wastewater samples. This criterion ensures that the pollutant was present in sufficient concentrations at sites where EPA evaluated treatment performance. This is used as a screening tool to identify those pollutants that are quantified in a wastestream at sufficient frequency and at treatable levels.

Using 10 times the baseline value as a screening threshold can facilitate evaluations of treatment system performance and efficacy, since it ensures the influent concentrations are high enough to more readily quantify the degree of pollutant removal resulting from treatment processes such as chemical or biological removal. However, the criterion is less applicable in cases where the technology basis results in complete removal of all pollutants present, such as would occur under the technology options considered for fly ash transport water, bottom ash transport water, and FGMC wastewater. For these "zero discharge" technologies, confirmation that the pollutant is present in the wastestream at quantifiable levels may be sufficient to identify a pollutant as a pollutant of concern. Additionally, in past effluent guidelines rulemakings, EPA has determined that a lower threshold (e.g., 5 times the baseline value) was the appropriate criterion for identifying pollutants of concern. For example, see Section 7 of the Technical Development Document for the Final Effluent Limitations Guidelines and Standards for the Meat and Poultry Products Point Source Category (40 CFR 432) (EPA-821-R-04-011).
EPA used the baseline values that were developed for the 2000 Centralized Waste Treatment (CWT) Industry Effluent Limitations Guidelines for this analysis. The baseline values are generally equal to the nominal quantitation limit identified for the analytical method for a pollutant. For the CWT ELGs, the Agency made several exceptions to this general rule if it determined that reliable measurements of a pollutant could be made at a lower level, or if the nominal quantitation limit could not be reasonably achieved, or if a single baseline value had to be selected when a pollutant had multiple nominal quantitation limits. Generally, the CWT ELGs used the instrument detection limit for EPA Method 1620 as the basis for the metals baseline values, with some exceptions. For the steam electric proposed ELGs, EPA analyzed the samples using EPA Methods 200.7, 200.8 with collision cell, and 1631E. Each of these methods is capable of achieving quantitation limits that are lower than the baseline values from CWT. However, EPA used the CWT baseline values, in most cases, as a more conservative value for the analysis. EPA did make a couple of exceptions and used the minimum level for mercury defined in EPA Method 1631E (i.e., 0.5 ng/L). Additionally, EPA used 2.0 μg/l for arsenic, which is based on a method detection limit study conducted by EPA [CSC, 2013]. Table 3-1 presents the baseline values used for the identification of POCs associated with the proposed Steam Electric ELGs.
Table 3-1. Baseline Values for Steam Electric Industry POCs

                                      POC
                                     Unit
                                Baseline Value
Classicals or Conventionals
   Ammonia as Nitrogen
                                     μg/l
50.0
   Biochemical Oxygen Demand
                                     μg/l
2,000.0
   Chemical Oxygen Demand
                                     μg/l
5,000.0
   Chloride
                                     μg/l
1,000.0
   Nitrate/Nitrite
                                     μg/l
50.0
   Total Cyanide
                                     μg/l
 20.0
   Total Dissolved Solids
                                     μg/l
10,000.0
   Total Phosphorus
                                     μg/l
10.0
   Total Sulfide
                                     μg/l
1,000.0
   Total Suspended Solids
                                     μg/l
 4,000.0
Metals
   Aluminum
                                     μg/l
200.0
   Antimony
                                     μg/l
20.0
   Arsenic
                                     μg/l
2.0
   Barium
                                     μg/l
200.0
   Beryllium
                                     μg/l
5.0
   Boron
                                     μg/l
100.0
   Cadmium
                                     μg/l
5.0
   Calcium
                                     μg/l
5,000.0
   Chromium
                                     μg/l
10.0
   Cobalt
                                     μg/l
50.0
   Copper
                                     μg/l
25.0
   Iron
                                     μg/l
100.0
   Lead
                                     μg/l
50.0
   Magnesium
                                     μg/l
5,000.0
   Manganese
                                     μg/l
15.0
   Mercury
                                     μg/l
0.0005
   Molybdenum
                                     μg/l
10.0
   Nickel
                                     μg/l
40.0
   Phosphorus
                                     μg/l
1,000.0
   Potassium
                                     μg/l
1,000.0
   Selenium
                                     μg/l
5.0
   Sodium
                                     μg/l
5,000.0
   Sulfur
                                     μg/l
1,000.0
   Thallium
                                     μg/l
10.0
   Titanium
                                     μg/l
5.0
   Vanadium
                                     μg/l
50.0
   Zinc
                                     μg/l
20.0
Source: Development Document for Effluent Limitations Guidelines and Standards for the Centralized Waste Treatment Industry, [EPA, 2000]; EPA Method 1631E, [CSC, 2013].

For some pollutants, EPA did not have a baseline value identified from the 2000 CWT ELGs. For these pollutants, EPA used the sample-specific method detection limit (MDL) for the analysis. For some wastestreams (e.g., ash transport water), there were analytes that did not have a baseline value nor a sample-specific MDL; therefore, these analytes were not included in the analysis and were not identified as a POC for the specific wastestream. Using the criteria described above, EPA developed lists of POCs for each fuel combustion wastewater: FGD wastewater, fly ash transport water, bottom ash transport water, landfill combustion residual leachate, impoundment combustion residual leachate, FGMC wastewater, and gasification wastewater.
Results
This section of the memorandum describes the results of the POC analysis for each of the wastestreams for which EPA is proposing revisions to the ELG.
FGD Wastewater Pollutants of Concern
EPA identified 35 POCs for FGD wastewater using the criteria presented in Section 3. Table 4-1 presents the number of samples analyzed for each pollutant in FGD wastewater, the number of sample results that were not detected above the quantitation limit, and the percentage of sample results that were detected at a concentration greater than ten times the baseline value. Table 4-2 lists the POCs identified for FGD wastewater.
Table 4-1. POC Analysis for FGD Wastewater

                                   Pollutant
                          Number of Samples Analyzed
                         Number of Non Detect Results
              Percentage of Sample Results >10x Baseline Value
                             Identified as a POC?
Conventional Pollutants
   Biochemical Oxygen Demand
                                      28
                                       5
                                      4%
                                      No
   Total Suspended Solids
                                      28
                                       0
                                     100%
                                      Yes
Priority Pollutants
   Antimony
                                      28
                                       7
                                      18%
                                      Yes
   Arsenic
                                      28
                                       0
                                     100%
                                      Yes
   Beryllium
                                      28
                                       4
                                      29%
                                      Yes
   Cadmium
                                      28
                                       7
                                      43%
                                      Yes
   Chromium
                                      28
                                       0
                                     100%
                                      Yes
   Copper
                                      28
                                       0
                                      71%
                                      Yes
   Cyanide, Total
                                      28
                                       4
                                      57%
                                      Yes
   Lead
                                      28
                                       0
                                      43%
                                      Yes
   Mercury
                                      28
                                       0
                                      57%
                                      Yes
   Nickel
                                      28
                                       0
                                      71%
                                      Yes
   Selenium
                                      28
                                       0
                                     100%
                                      Yes
   Silver
                                      28
                                      27
                                      4%
                                      No
   Thallium
                                      28
                                       3
                                      43%
                                      Yes
   Zinc
                                      28
                                       0
                                     100%
                                      Yes
Nonconventional Pollutants
   Aluminum
                                      28
                                       0
                                     100%
                                      Yes
   Ammonia
                                      28
                                       7
                                      75%
                                      Yes
   Barium
                                      28
                                       0
                                      43%
                                      Yes
   Boron
                                      28
                                       0
                                     100%
                                      Yes
   Calcium
                                      28
                                       0
                                     100%
                                      Yes
   Chemical Oxygen Demand
                                      28
                                       1
                                      96%
                                      Yes
   Cobalt
                                      28
                                       0
                                      43%
                                      Yes
   Iron
                                      28
                                       0
                                     100%
                                      Yes
   Magnesium
                                      28
                                       0
                                     100%
                                      Yes
   Manganese
                                      28
                                       0
                                     100%
                                      Yes
   Molybdenum
                                      28
                                       3
                                      71%
                                      Yes
   Nitrate Nitrite as N
                                      28
                                       0
                                     100%
                                      Yes
   Nitrogen, Kjeldahl
                                      28
                                       0
                                     100%
                                      Yes
   Phosphorus, Total
                                      28
                                      10
                                      29%
                                      Yes
   Sodium
                                      28
                                       0
                                      71%
                                      Yes
   Sulfate
                                      28
                                       0
                                     100%
                                      Yes
   Tin
                                      28
                                      28
                                      0%
                                      No
   Titanium
                                      28
                                       0
                                     100%
                                      Yes
   Total Dissolved Solids
                                      28
                                       0
                                     100%
                                      Yes
   Vanadium
                                      28
                                       0
                                      61%
                                      Yes
   Chloride
                                      28
                                       0
                                     100%
                                      Yes
Source: EPA Sampling Data, [ERG, 2012b  -  2012h]; Progress Energy Data, [NCDENR, 2011]; Duke Energy Data, [Duke Energy, 2011a-2011b].

Table 4-2. Pollutants of Concern  -  FGD Wastewater

                                Pollutant Group
                             Pollutant of Concern
Conventional Pollutants
                               Oil and Grease[a]

                            Total Suspended Solids
Priority Pollutants
                                   Antimony

                                    Arsenic

                                   Beryllium

                                    Cadmium

                                   Chromium

                                    Copper

                                    Cyanide

                                     Lead

                                    Mercury

                                    Nickel
Priority Pollutants
                                   Selenium

                                   Thallium

                                     Zinc
Nonconventional Pollutants

                                   Aluminum

                                    Ammonia

                                    Barium

                                     Boron

                                    Calcium

                            Chemical Oxygen Demand

                                   Chloride

                                    Cobalt

                                     Iron

                                   Magnesium

                                   Manganese

                                  Molybdenum

                                Nitrate/Nitrite

                              Nitrogen, Kjeldahl

                                  Phosphorus

                                    Sodium

                                    Sulfate

                                   Titanium

                            Total Dissolved Solids

                                   Vanadium
Source: [ERG, 2012b  -  2012h].
a  -  EPA did not analyze its field sampling data for oil and grease. Rather, since the existing steam electric ELGs currently contain BPT limitations applicable to FGD wastewater for oil and grease, EPA already has data from the existing rulemaking demonstrating oil and grease is also a pollutant of concern in FGD wastewater.


Ash Transport Water Pollutants of Concern
EPA identified 24 POCs using the criteria presented in Section 3. Table 4-3 presents the number of samples analyzed for each pollutant in ash transport water, the number of sample results that were not detected above the quantitation limit, and the percentage of sample results that were detected at a concentration greater than ten times the baseline value.
EPA also identified selenium as a POC for fly ash transport water based on a study conducted at Belews Lake that linked fish kills to selenium accumulation in the lake associated with discharges from a power plant, as well as other documented instances of harm caused by discharges of selenium in ash transport water [Lemly, 1985]. As discussed above in Section 3, the criterion EPA used as a screening tool to identify pollutants of concern is less applicable in cases where the technology basis results in complete removal of all pollutants present, such as would occur under the technology options considered for fly ash transport water, bottom ash transport water, and FGMC wastewater. For these "zero discharge" technologies, confirmation that the pollutant is present in the wastestream at quantifiable levels may be sufficient to identify a pollutant as a pollutant of concern. Based on the information in the record for selenium in ash transport water, EPA identified it as a pollutant of concern. Table 4-4 lists the POCs identified for ash transport water.
Table 4-3. POC Analysis for Ash Transport Water

                                   Pollutant
                          Number of Samples Analyzed
                         Number of
Non Detect Results
             Percentage of Sample Results >10x 
Baseline Value
                             Identified as a POC?
Conventional Pollutants
   Total Suspended Solids
                                       1
                                       0
                                     100%
                                      Yes
   Biochemical Oxygen Demand
                                       1
                                       0
                                      0%
                                      No
Priority Pollutants
   Antimony
                                       2
                                       1
                                      0%
                                      No
   Arsenic
                                       2
                                       0
                                     100%
                                      Yes
   Beryllium
                                       1
                                       0
                                     100%
                                      Yes
   Cadmium
                                       2
                                       0
                                      0%
                                      No
   Chromium
                                       2
                                       0
                                     100%
                                      Yes
   Copper
                                       2
                                       0
                                     100%
                                      Yes
   Lead
                                       2
                                       0
                                      50%
                                      Yes
   Mercury
                                       2
                                       0
                                     100%
                                      Yes
   Nickel
                                       2
                                       0
                                      50%
                                      Yes
   Selenium
                                       2
                                       2
                                      0%
                                      No
   Silver
                                       2
                                       2
                                      0%
                                      No
   Thallium
                                       2
                                       1
                                      0%
                                      No
   Zinc
                                       2
                                       0
                                     100%
                                      Yes
Nonconventional Pollutants
   Aluminum
                                       1
                                       0
                                     100%
                                      Yes
   Ammonia
                                       1
                                       0
                                      0%
                                      No
   Barium
                                       1
                                       0
                                     100%
                                      Yes
   Boron
                                       1
                                       0
                                     100%
                                      Yes
   Calcium
                                       1
                                       0
                                     100%
                                      Yes
   Chloride
                                       1
                                       0
                                     100%
                                      Yes
   Cobalt
                                       1
                                       0
                                      0%
                                      No
   Hexane Extractable Material
                                       1
                                       0
                              No Baseline or MDL
                              No Baseline or MDL
   Iron
                                       1
                                       0
                                     100%
                                      Yes
   Magnesium
                                       1
                                       0
                                      0%
                                      No
   Manganese
                                       1
                                       0
                                     100%
                                      Yes
   Molybdenum
                                       1
                                       0
                                     100%
                                      Yes
   Nitrate/Nitrite
                                       1
                                       0
                                     100%
                                      Yes
   Nitrogen, Kjeldahl
                                       1
                                       0
                              No Baseline or MDL
                              No Baseline or MDL
   Phosphorus, Total
                                       1
                                       0
                                      0%
                                      No
   SGT-HEM
                                       1
                                       0
                                      0%
                                      No
   Sodium
                                       1
                                       0
                                     100%
                                      Yes
   Sulfate
                                       1
                                       0
                              No Baseline or MDL
                              No Baseline or MDL
   Tin
                                       1
                                       1
                                      0%
                                      No
   Titanium
                                       1
                                       0
                                     100%
                                      Yes
   Total Dissolved Solids
                                       1
                                       0
                                     100%
                                      Yes
   Vanadium
                                       1
                                       0
                                     100%
                                      Yes
   Yttrium
                                       1
                                       0
                                     100%
                                      Yes
Source: Cardinal Sampling Data, [ERG, 2008].

Table 4-4. Pollutants of Concern  -  Ash Transport Water

                                Pollutant Group
                             Pollutant of Concern
Conventional Pollutants
                               Oil and Grease[a]

                            Total Suspended Solids
Priority Pollutants
                                    Arsenic

                                   Beryllium

                                   Chromium

                                    Copper

                                     Lead

                                    Mercury

                                    Nickel

                                   Selenium

                                     Zinc
Nonconventional Pollutants
                                   Aluminum

                                    Barium

                                     Boron

                                    Calcium

                                   Chloride

                                     Iron
Nonconventional Pollutants
                                   Manganese

                                  Molybdenum

                                Nitrate/Nitrite

                                    Sodium

                                   Titanium

                            Total Dissolved Solids

                                   Vanadium

                                    Yttrium
Source: Cardinal Sampling Data, [ERG, 2008].
a  -  EPA did not analyze its field sampling data for oil and grease. Rather, since the existing steam electric ELGs currently contain BPT limitations applicable to fly ash transport water for oil and grease, EPA already has data from the existing rulemaking demonstrating oil and grease is also a pollutant of concern in fly ash transport water.

Constituents present in ash, and therefore ash transport water, are primarily derived from the type of coal/petroleum coke burned; therefore, EPA expects that the bottom ash transport water will have the same constituents that are found in the fly ash transport water. For this reason, EPA assumed that the POCs for bottom ash transport water are identical to those of fly ash transport water.

Impoundment and Landfill Leachate Pollutants of Concern
EPA identified 16 POCs for combustion residual landfill leachate and 13 POCs for combustion residual impoundment leachate, using the criteria presented in Section 3. Table 4-5 presents the number of samples analyzed for each pollutant in the combustion residual landfill leachate, the number of sample results that were not detected above the quantitation limit, and the percentage of sample results that were detected at a concentration greater than ten times the baseline value. Table 4-6 lists the POCs identified for combustion residual landfill leachate. Table 4-7 presents the number of samples analyzed for each pollutant in the combustion residual impoundment leachate, the number of sample results that were not detected above the quantitation limit, and the percentage of sample results that were detected at a concentration greater than ten times the baseline value. Table 4-8 lists the POCs identified for combustion residual impoundment leachate.

Table 4-5. POC Analysis for Landfill Leachate

                                   Pollutant
                          Number of Samples Analyzed
                         Number of Non Detect Results
                 Percentage of Sample Results >10x Baseline
                             Identified as a POC?
Conventional Pollutants
   Total suspended solids (TSS)
                                      225
                                      91
                                      12%
                                      Yes
Priority Pollutants
   Antimony
                                      226
                                      133
                                      0%
                                      No
   Arsenic
                                      233
                                      49
                                      46%
                                      Yes
   Beryllium
                                      225
                                      200
                                      0%
                                      No
   Cadmium
                                      231
                                      110
                                      7%
                                      No
   Chromium
                                      231
                                      140
                                      7%
                                      No
   Copper
                                      233
                                      121
                                      0%
                                      No
   Lead
                                      223
                                      174
                                      0%
                                      No
   Mercury
                                      231
                                      46
                                      48%
                                      Yes
   Nickel
                                      229
                                      65
                                      4%
                                      No
   Selenium
                                      233
                                      42
                                      28%
                                      Yes
   Silver
                                      222
                                      211
                                      1%
                                      No
   Thallium
                                      225
                                      152
                                      0%
                                      No
   Zinc
                                      226
                                      107
                                      7%
                                      No
Nonconventional Pollutants
   Aluminum
                                      225
                                      72
                                      12%
                                      Yes
   Barium
                                      233
                                       8
                                      0%
                                      No
   Boron
                                      233
                                       6
                                      86%
                                      Yes
   Calcium
                                      233
                                       2
                                      90%
                                      Yes
   Chlorides
                                      232
                                       6
                                      81%
                                      Yes
   Cobalt
                                      229
                                      94
                                      2%
                                      No
   Iron
                                      227
                                      58
                                      26%
                                      Yes
   Magnesium
                                      233
                                       6
                                      37%
                                      Yes
   Manganese
                                      231
                                      26
                                      64%
                                      Yes
   Molybdenum
                                      233
                                      19
                                      65%
                                      Yes
   Sodium
                                      233
                                       2
                                      63%
                                      Yes
   Sulfate
                                      232
                                       1
                                      98%
                                      Yes
   Tin
                                      224
                                      217
                                      0%
                                      No
   Titanium
                                      223
                                      167
                                      5%
                                      No
   Total dissolved solids (TDS)
                                      232
                                       0
                                      95%
                                      Yes
   Vanadium
                                      229
                                      100
                                      5%
                                      No
Source: Steam Electric Survey, [ERG, 2012a];

Table 4-6. Pollutants of Concern  -  Landfill Leachate

                                Pollutant Group
                             Pollutant of Concern
Conventional Pollutants
                               Oil and Grease[a]

                            Total Suspended Solids
Priority Pollutants
                                    Arsenic

                                    Mercury

                                   Selenium
Nonconventional Pollutants
                                   Aluminum

                                     Boron

                                    Calcium

                                   Chlorides

                                     Iron

                                   Magnesium

                                   Manganese

                                  Molybdenum

                                    Sodium

                                    Sulfate

                            Total Dissolved Solids
Source: Steam Electric Survey, [ERG, 2012a];
a  -  The landfill leachate samples were not analyzed for oil and grease (O&G). Rather, since the existing steam electric ELGs currently contain BPT limitations applicable to combustion residual leachate for O&G, EPA already has data from the existing rulemaking demonstrating O&G is also a pollutant of concern in combustion residual leachate.

Table 4-7. POC Analysis for Impoundment Leachate

                                   Pollutant
                          Number of Samples Analyzed
                         Number of Non Detect Results
                Percentage of Sample Results 
>10x Baseline
                             Identified as a POC?
Conventional Pollutants
   Total suspended solids (TSS)
                                      85
                                      38
                                      5%
                                      No
Priority Pollutants
   Antimony
                                      85
                                      54
                                      0%
                                      No
   Arsenic
                                      81
                                      14
                                      28%
                                      Yes
   Beryllium
                                      81
                                      64
                                      0%
                                      No
   Cadmium
                                      81
                                      41
                                      0%
                                      No
   Chromium
                                      81
                                      65
                                      0%
                                      No
   Copper
                                      84
                                      32
                                      0%
                                      No
   Lead
                                      81
                                      52
                                      0%
                                      No
   Mercury
                                      82
                                      19
                                      11%
                                      Yes
   Nickel
                                      85
                                      10
                                      0%
                                      No
   Selenium
                                      81
                                      43
                                      5%
                                      No
   Silver
                                      81
                                      78
                                      0%
                                      No
   Thallium
                                      81
                                      50
                                      0%
                                      No
   Zinc
                                      81
                                      16
                                      5%
                                      No
Nonconventional Pollutants
   Aluminum
                                      85
                                      30
                                      0%
                                      No
   Barium
                                      85
                                       0
                                      0%
                                      No
   Boron
                                      85
                                       0
                                      56%
                                      Yes
   Calcium
                                      85
                                       0
                                      89%
                                      Yes
   Chlorides
                                      85
                                       0
                                      75%
                                      Yes
   Cobalt
                                      85
                                      19
                                      0%
                                      No
   Iron
                                      85
                                       9
                                      39%
                                      Yes
   Magnesium
                                      85
                                       0
                                      25%
                                      Yes
   Manganese
                                      85
                                       1
                                      75%
                                      Yes
   Molybdenum
                                      85
                                      18
                                      22%
                                      Yes
   Sodium
                                      85
                                       0
                                      27%
                                      Yes
   Sulfate
                                      85
                                       0
                                      96%
                                      Yes
   Tin
                                      81
                                      76
                                      5%
                                      No
   Titanium
                                      81
                                      52
                                      1%
                                      No
   Total dissolved solids (TDS)
                                      85
                                       0
                                      99%
                                      Yes
   Vanadium
                                      81
                                      66
                                      0%
                                      No
Source: Steam Electric Survey, [ERG, 2012a].


Table 4-8. Pollutants of Concern  -  Impoundment Leachate

                                Pollutant Group
                             Pollutant of Concern
Conventional Pollutants
                               Oil and Grease[a]
Priority Pollutants
                                    Arsenic

                                    Mercury
Nonconventional Pollutants
                                     Boron

                                    Calcium

                                   Chlorides

                                     Iron

                                   Magnesium

                                   Manganese

                                  Molybdenum

                                    Sodium

                                    Sulfate

                            Total Dissolved Solids
Source: Steam Electric Survey, [ERG, 2012a]
a  -  The impoundment leachate samples were not analyzed for O&G. Rather, since the existing steam electric ELGs currently contain BPT limitations applicable to combustion residual leachate for O&G, EPA already has data from the existing rulemaking demonstrating O&G is also a pollutant of concern in combustion residual leachate.

Gasification Pollutants of Concern
EPA identified 20 POCs for gasification wastewater using the criteria presented in Section 3. Table 4-9 presents the number of samples analyzed for each pollutant in gasification wastewater, the number of sample results that were not detected above the quantitation limit, and the percentage of sample results that were detected at a concentration greater than ten times the baseline value. Table 4-10 lists the POCs identified for gasification wastewater.

              Table 4-9. POC Analysis for Gasification Wastewater
                                       
                                   Pollutant
                          Number of Samples Analyzed
                         Number of Non Detect Results
                 Percentage of Sample Results >10x Baseline
                                     POC?
Conventional Pollutants
   Total Suspended Solids
                                      20
                                      13
                                      0%
                                      No
   Biochemical Oxygen Demand
                                      20
                                       5
                                      55%
                                      Yes
Priority Pollutants
   Antimony
                                      20
                                      16
                                      20%
                                      Yes
   Arsenic
                                      20
                                      10
                                      40%
                                      Yes
   Beryllium
                                      20
                                      16
                                      0%
                                      No
   Cadmium
                                      20
                                      18
                                      0%
                                      No
   Chromium
                                      20
                                      16
                                      0%
                                      No
   Copper
                                      20
                                      16
                                      0%
                                      No
   Cyanide, Total
                                      20
                                       6
                                      70%
                                      Yes
   Lead
                                      20
                                      13
                                      0%
                                      No
   Mercury
                                      20
                                       7
                                      65%
                                      Yes
   Nickel
                                      20
                                      12
                                      20%
                                      Yes
   Selenium
                                      20
                                       0
                                      95%
                                      Yes
   Silver
                                      20
                                      20
                                      0%
                                      No
   Thallium
                                      20
                                       9
                                      10%
                                      Yes
   Zinc
                                      20
                                      16
                                      0%
                                      No
Nonconventional Pollutants
   Aluminum
                                      20
                                      15
                                      25%
                                      Yes
   Ammonia
                                      20
                                       0
                                     100%
                                      Yes
   Barium
                                      20
                                      16
                                      0%
                                      No
   Boron
                                      20
                                       3
                                      80%
                                      Yes
   Calcium
                                      20
                                       8
                                      0%
                                      No
   Chemical Oxygen Demand
                                      20
                                       5
                                      75%
                                      Yes
   Chloride
                                      20
                                       0
                                     100%
                                      Yes
   Cobalt
                                      20
                                      20
                                      0%
                                      No
   Iron
                                      20
                                       3
                                      45%
                                      Yes
   Magnesium
                                      20
                                      12
                                      0%
                                      No
   Manganese
                                      20
                                      15
                                      10%
                                      Yes
   Molybdenum
                                      20
                                      18
                                      0%
                                      No
   Nitrate Nitrite as N
                                      20
                                      14
                                      20%
                                      Yes
   Nitrogen, Kjeldahl
                                      20
                                       2
                                      90%
                                      Yes
   Phosphorus, Total
                                      20
                                       1
                                      0%
                                      No
   Sodium
                                      20
                                       4
                                      80%
                                      Yes
   Sulfate
                                      20
                                      11
                                      45%
                                      Yes
   Tin
                                      20
                                      20
                                      0%
                                      No
   Titanium
                                      20
                                      18
                                      0%
                                      No
   Total Dissolved Solids
                                      20
                                       2
                                      90%
                                      Yes
   Vanadium
                                      20
                                       9
                                      0%
                                      No
Source: CWA 308 Monitoring Data, [ERG, 2012i].


Table 4-10. Pollutants of Concern  -  Gasification Wastewater

                                Pollutant Group
                             Pollutant of Concern
Conventional Pollutants
                           Biochemical Oxygen Demand
Priority Pollutants
                                   Antimony

                                    Arsenic

                                    Cyanide

                                    Mercury

                                    Nickel

                                   Selenium

                                   Thallium
Nonconventional Pollutants
                                   Aluminum

                                    Ammonia

                                     Boron

                            Chemical Oxygen Demand

                                   Chloride

                                     Iron

                                   Manganese

                                Nitrate/Nitrite

                              Nitrogen, Kjeldahl

                                    Sodium

                                    Sulfate

                            Total Dissolved Solids
Source: CWA 308 Monitoring Data, [ERG, 2012i]

1.0.1 Flue Gas Mercury Control Wastewater Pollutants of Concern
As described in Section 6.4 of the Technical Development Document, for activated carbon injection (ACI) systems, the activated carbon can either be injected upstream or downstream of the primary particulate removal system. When the activated carbon is injected upstream of the primary particulate removal system, the FGMC waste is captured with the fly ash removed by the system. When the activated carbon is injected downstream of the primary particulate removal system, the FGMC waste must be collected in a separate particulate removal system, typically a fabric filter baghouse, and residual fly ash that passes through the primary particulate removal system may also be captured in the system.
The FGMC waste/fly ash from either of these configurations can be handled using either a wet sluicing system or dry handling system. Based on process knowledge and engineering judgment, EPA concluded that the pollutants of concern for FGMC wastewater are likely to be identical to the pollutants of concern identified for fly ash transport water. This is due to the fact that, when activated carbon is injected into the flue gases, the carbon intermixes with the fly ash particles, and then the commingled mixture of activated carbon (which adsorbs mercury and other pollutants from the flue gases) and fly ash particles is captured together and transferred to the FGMC wastewater. Based on this conclusion, EPA identified 25 POCs associated with FGMC wastewater. Table 4-11 lists the POCs identified for FGMC wastewater, which is the same as the list for fly ash transport water.
Table 4-11. Pollutants of Concern  -  Flue Gas Mercury Control Wastewater

                                Pollutant Group
                             Pollutant of Concern
Conventional Pollutants
                               Oil and Grease[a]

                            Total Suspended Solids
Priority Pollutants
                                    Arsenic
1. --------------------------------------------------------------------------------

                                   Beryllium
2. --------------------------------------------------------------------------------

                                   Chromium
3. --------------------------------------------------------------------------------

                                    Copper
4. --------------------------------------------------------------------------------

                                     Lead
5. --------------------------------------------------------------------------------

                                    Mercury
6. --------------------------------------------------------------------------------

                                    Nickel
7. --------------------------------------------------------------------------------

                                   Selenium
8. --------------------------------------------------------------------------------

                                     Zinc
Nonconventional Pollutants
                                   Aluminum
9. --------------------------------------------------------------------------------

                                     Boron
10. --------------------------------------------------------------------------------

                                    Barium
11. --------------------------------------------------------------------------------

                                    Calcium
12. --------------------------------------------------------------------------------

                                   Chloride
13. --------------------------------------------------------------------------------

                                     Iron
14. --------------------------------------------------------------------------------

                                   Manganese
15. --------------------------------------------------------------------------------

                                  Molybdenum
16. --------------------------------------------------------------------------------

                               Nitrate/Nitrite 
17. --------------------------------------------------------------------------------

                                    Sodium
18. --------------------------------------------------------------------------------

                                   Titanium
19. --------------------------------------------------------------------------------

                            Total Dissolved Solids
20. --------------------------------------------------------------------------------

                                   Vanadium
21. --------------------------------------------------------------------------------

                                    Yttrium
Source: [ERG, 2008].
Nonchemical Metal Cleaning Wastes Pollutants of Concern
As part of the 1974 rulemaking, EPA collected characterization data associated with chemical and nonchemical metal cleaning wastes. Based on the data collected during that rulemaking, EPA determined that TSS, oil & grease (O&G), copper, and iron were pollutants of concern for metal cleaning waste warranting regulation. As such, EPA set BPT limitations for these four pollutants in discharges of metal cleaning wastes, including both nonchemical and chemical cleaning wastes. For additional information regarding the pollutants that may be present in nonchemical metal cleaning wastes, see the 1974 Development Document for Effluent Limitations Guidelines and New Source Performance Standards for the Steam Electric Power Generating Point Source Category [U.S. EPA, 1974]. 
Based on this assessment, EPA determined that TSS, O&G, copper, and iron are POCs for nonchemical metal cleaning wastes. Table 4-12 presents the four POCs for nonchemical metal cleaning wastes. 
Table 4-12. Pollutants of Concern  -  Nonchemical Metal Cleaning Wastes

                                Pollutant Group
                             Pollutant of Concern
Priority Pollutants
                                    Copper
Conventional Pollutants
                            Total Suspended Solids

                               Oil & Grease
Nonconventional Pollutants
                                     Iron
Source: [U.S. EPA, 1974].

References
1. Computer Sciences Corporation (CSC). 2013. Results of the ICP/MS Collision Cell Method Detection Limit Studies in the Synthetic Flue Gas Desulfurization Matrix. (16 January). DCN SE03872.
2. Duke Energy. 2011a Industry Provided Sampling Data from Duke Energy's Belews Creek Steam Station. (17 August). DCN SE01808.
3. Duke Energy. 2011b Industry Provided Sampling Data from Duke Energy's Allen Steam Station. (17 August). DCN SE01809.
4. Eastern Research Group (ERG). 2008. Final Sampling Episode Report, Buckeye Power Company's Cardinal Power Plant. (August 26). DCN SE02107.
5. Eastern Research Group (ERG). 2012a. Steam Electric Technical Questionnaire Database ("Steam Electric Survey"). (Date). DCN SE01958.
6. Eastern Research Group (ERG). 2012b. Final Sampling Episode Report, Duke Energy Carolinas' Belews Creek Steam Station. (13 April). DCN SE01305.
7. Eastern Research Group (ERG). 2012c. Final Sampling Episode Report, We Energies' Pleasant Prairie Power Plant. (13 April). DCN SE01306.
8. Eastern Research Group (ERG). 2012d. Final Sampling Episode Report, Duke Energy Miami Fort Station. (13 April). DCN SE01304.
9. Eastern Research Group (ERG). 2012e. Final Sampling Episode Report, Duke Energy Carolinas' Allen Steam Station. (13 April). DCN SE01307.
10. Eastern Research Group (ERG). 2012f. Final Sampling Episode Report, Mirant Mid-Atlantic, LLC's Dickerson Generating Station. (13 April). DCN SE01308.
11. Eastern Research Group (ERG). 2012g. Final Sampling Episode Report, Allegheny Energy's Hatfield's Ferry Power Station. (13 April). DCN SE01310.
12. Eastern Research Group (ERG). 2012h. Final Sampling Episode Report, RRI Energy's Keystone Generating Station. (13 April). DCN SE01309.
13. Eastern Research Group (ERG). 2012i. Final Power Plant Monitoring Data Collected Under Clean Water Act Section 308 Authority ("CWA 308 Monitoring Data"). (30 May). DCN SE01326.
14. NCDENR. 2011. North Carolina Department of Environment and Natural Resources (NCDENR). State Provided Sampling Data from North Carolina's Progress Energy Roxboro Plant. (26 June). DCN SE01812.
15. U.S. EPA. 1974. Development Document for Effluent Limitations Guidelines and New Source Performance Standards for the Steam Electric Power Generating Point Source Category. Washington, D.C. (October). DCN SE02917.
16. U.S. EPA, 2000. Development Document for Effluent Limitations Guidelines and Standards for the Centralized Waste Treatment Industry. (August). DCN SE02920.
