Water

OPERATING EXPERIENCE AND PLANT DATA ON WASTE WATER DISCHARGES

Detailed analyses have been conducted on process wastewater discharged at the Wabash River IGCC power plant. Results were reported for metals, cyanide, ammonia, and water quality (e.g., pH), but excluded sulfides, other anions, and organic compounds. Streams included were cooling tower blowdown; gasification plant process waste water; regeneration waste water from the demineralizer in the power block; rainwater collected in both the gasification and the power blocks; equipment purges (blowdowns) and water wash-downs during maintenance preparation procedures; and un-recycled condensed water from the process cooling water was not tested. Results are presented in Table 1.

Table 1. Wabash River Process Waste Water Discharge1

PARAMETER/ CONSTITUENT UNIT PERMIT LEVEL MONTHLY AVERAGE PERMIT LEVEL DAILY MAXIMUM 1997
MONTHLY AVERAGE
1998
MONTHLY AVERAGE
1999
MONTHLY AVERAGE
Ammonia (as Nitrogen) mg/l 27.14 54.29 3.93 6.56 8.8
Arsenic mg/l 0.018 0.043 0.0077 0.0199a <0.01
Cadmium mg/l 0.010 0.025 <0.0038 <0.008 <0.01
Chromium mg/l 3.47 8.07 <0.006 <0.0108 <0.0167
Hexavalent Chromium mg/l 0.014 0.032 <0.01 <0.0120 <0.01
Copper mg/l 0.040 0.093 <0.01 <0.0145 0.0185
Cyanide mg/l 0.019 0.044 0.107a 0.2798a 0.1438a
Lead mg/l 0.260 0.606 <0.08 <0.08 <0.08
Mercury mg/l 0.0005 0.001 <0.005 <0.0005 <0.0006
Nickel mg/l 2.91 6.78 <0.02 <0.0236 <0.1140
Selenium mg/l 0.017 0.040 0.0714a 0.230a 0.1380a
Zinc mg/l 0.241 0.560 0.05 0.0414 0.1363
pH mg/l 6.0 to 9.0 6.0 to 9.0 7.99 8.4 7.5

Process water from the Wabash facility originally demonstrated out of compliance levels for arsenic, cyanide and selenium. While not included in the table, daily maximums routinely exceeded permit levels for cyanide and selenium and occasionally for arsenic. However, installation of a wastewater mechanical vapor recompression (MVR) system in 2001, like the system described earlier for the Polk plant, has apparently solved this problem. This treatment method strips and dehydrates (to a salt) the majority of the contaminants in a selected process wastewater stream with beneficial water re-use of the condensed vapor.2

Similar tests were conducted on the treated wastewater from the Dow Chemical’s Louisiana Gasification Technologies Inc. (LGTI) IGCC plant. Results are presented in Table 2 for many of the same analytes listed in Table 1. The major differences between LGTI results and those at Wabash deal with lead and cyanide. Both are an order of magnitude higher at LGTI. The Wabash facility, however, is more representative of current state-of-the-art performance of wastewater treatment equipment. The LGTI plant also had experienced elevated cyanide levels in their wastewater discharge. Total average cyanide levels were measured to be 1.5 mg/l, with a 95% confidence interval of 0.3 to 2.7 mg/l. Average ammonia content (as nitrogen) was measured to be 7.3 mg/l in the treated process wastewater, which corroborates the levels measured at the Wabash River plant.

Table 2. LGTI River Process Waste Water Discharge Analytes—Ammonia, Cyanide, Metals, Water Quality3

ANALYTE UNITS AVERAGE 95% CONFIDENCE LEVEL
Ammonia (as Nitrogen) mg/l 7.3 3.6
Arsenic mg/l 0.0038 0.0024
Beryllium mg/l 0.0006 0.0013
Cadmium mg/l 0.005 0.0024
Chloride mg/l 0.88 0.15
Chromium mg/l 0.0087 0.003
Hexavalent Chromium mg/l - -
Copper mg/l 0.015 0.0044
Cyanide mg/l 1.5 1.2
Lead mg/l 0.33 0.25
Manganese mg/l 0.0024 0.0034
Mercury mg/l <0.00003 -
Nickel mg/l 0.022 0.042
Selenium mg/l 0.032 0.02
Zinc mg/l - -
pH mg/l 8.75 -
Chemical Oxygen Demand mg/l 53 3.9

Organic analytes were also measured in the treated wastewater discharge with results indicating very low concentrations of aldehydes, volatile organic compounds, and semi-volatile compounds.4 Table 3 provides a partial listing of the reported results. Note that these results will differ depending on the gasifier type, fuel, and water treatment methods employed in an IGCC plant.

Table 3. LGTI River Process Waste Water Discharge Analytes—Organic Compounds5

ANALYTE UNITS AVERAGE 95% CONFIDENCE LEVEL
ALDEHYDES
Acetaldehyde mg/l <0.01 Not Calculated
Acrolein mg/l <0.01 Not Calculated
Benzaldehyde mg/l <0.01 Not Calculated
Formaldehyde mg/l <0.01 Not Calculated
VOLATILE ORGANIC COMPOUNDS
1,1,1-Trichloroethane µg/l <0.87 Not Calculated
1,1-Dichloroethane µg/l <0.59 Not Calculated
Benzene µg/l <0.46 Not Calculated
Carbon disulfide µg/l <0.49 Not Calculated
Chlorobenzene µg/l <0.32 Not Calculated
Vinyl acetate µg/l <0.64 Not Calculated
SEMI-VOLATILE COMPOUNDS
1,2,4 -Trichlorobenzene µg/l <0.53 Not Calculated
1,2-Dichlorobenzene µg/l <0.64 Not Calculated
2-Fluorobiphenyl µg/l 61.2 15
Anthracene µg/l <0.70 Not Calculated
Benz(a)pyrene µg/l <0.70 Not Calculated
Benz(a)anthracene µg/l <0.77 Not Calculated
Pyrene µg/l 11 5.6

  1. Staff of Wabash River Energy Ltd, “Wabash River Coal Gasification Repowering Project-Final Technical Report,” Prepared under Cooperative Agreement with DOE: DE-FC21-92M29310, August 2000.
  2. Amick, P., “Power Industry: Gasification-Based Repowering of a Coal Fired Plant The Wabash River IGCC,” Global Energy Presentation to GTC Gasification Workshop, September 12, 2001.
  3. Staff of Wabash River Energy Ltd, “Wabash River Coal Gasification Repowering Project-Final Technical Report,” Prepared under Cooperative Agreement with DOE: DE-FC21-92M29310, August 2000.
  4. Williams, A., et al., “Trace Substance Emissions from a Coal-Fired Gasification Plant: Summary Report,” Report prepared for EPRI, U.S. DOE, and LGTI by Radian International, TR-106964, November 1996.
  5. Staff of Wabash River Energy Ltd, “Wabash River Coal Gasification Repowering Project-Final Technical Report,” Prepared under Cooperative Agreement with DOE: DE-FC21-92M29310, August 2000.

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