Mock Antidegradation Alternatives Analysis
Cooling Water System Chemical Change
Gilded Grist, LLC
May 2011
Table of Contents
Executive Summary
Existing Conditions and Design Parameters
Receiving Stream Network
Effluent Limitations
POC Identification and Tier Protection Level
Identification & Discussion of Alternatives
Alt. No. 1: Land Disposal
Alt. No. 2: Zero Blowdown
Alt. No. 3: Discontinue Use of Chemicals
Alt. No. 4: Continue Use of Chemical A
Alt. No. 5: Replace Chemical A with Chemical B
Preferred Alternative
Justification of Degradation
Project Social and Economic Importance
Appendix A
List of Tables
Table 1: Current Stream Designations
Table 2: UAA Status
Table 3: Impairment Status
Table 4: Existing NPDES Permit Limits (Outfall 001)
Table 5: Pollutants of Concern
Table 6: Alternatives and Present Worth Costs
Table 7: Alternative Classification and Evaluation
Gilded Grist, LLC
Antidegradation Alternatives Analysis
May 19, 2011
Executive Summary
Gilded Gristan ethanol production facility located in Pleasantville County near Anywhere, IA. Gilded Grist currently adds Chemical A to its cooling water system to prevent corrosion and scale formation. It is proposing to discontinue the use of Chemical A and replace it with Chemical B. Chemical B is believed to be a more effective chemical to prevent corrosion and scale formation.
A total of five alternatives were evaluated including the base pollution control alternative, 3 non-degrading alternatives and one less-degrading alternative. The alternatives were evaluated based on their practicability, economic efficiency, affordability and degradation on a pollutant-by-pollutant basis. Two of the non-degrading alternatives (Zero Blowdown and Discontinuing Use of Chemicals)were determined to be non-practicable while the third (Land Application) was found to be not economically efficient. The two remaining alternatives (Continued Use of Chemical A and Replacement of Chemical A with Chemical B) were found to be reasonable. Replacement of Chemical A with Chemical B was found to be the least degrading reasonable alternative and is the preferred alternative.
Although the preferred alternative is considered less degrading and expected to improve overall water quality in the receiving stream network, degradation for one pollutant of concern will occur. Therefore, a description of the project social and economic importance is included at the end of this analysis.
Existing Conditions and Design Parameters
Cooling tower blowdown is currently discharged via Outfall 001 which is listed in Gilded Grist’s NPDES permit. No other wastewater stream is combined with the blowdown prior to discharge. No change in discharge volumes is proposed and the discharge flow rates will remain the same as existing. A target concentration of 1 mg/L of Chemical A is currently maintained in the cooling tower with maximum observed concentrations of 2 mg/L. A target concentration of 2 mg/L of Chemical B is proposed for the cooling tower with a maximum concentration of 3 mg/L. Wastewater treatment is not currently required to meet effluent limitations of the NPDES permit and as such there are no additional applicable design parameters.
Receiving Stream Network
The existing discharge receiving stream network consists of an unnamed creek tributary to the Winnebago River. Downstream the Winnebago River is tributary to the Shell Rock River which is in turn tributary to the Cedar River. The Cedar River is tributary to the Iowa River shortly prior to the Iowa River’s confluence with the Mississippi River.
The current receiving stream network designations,Use Attainability Analysis (UAA)and impairment status are summarized in Tables 1, 2 and 3:
Table 1: Current Stream Designations
Stream / Current Designation / SourceUnnamed Cr. / General & A1, B(WW-1) / UAA & 567 IAC 61.3(1)b
Winnebago R. / A1, B(WW-1), HH / 2/17/10 Surface Water Classification Doc.
Shell Rock R. / A1, B(WW-1), HH / 2/17/10 Surface Water Classification Doc.
Cedar R. / A1, B(WW-1), HH, C / 2/17/10 Surface Water Classification Doc.
Iowa R. / A1, B(WW-1), HH / 2/17/10 Surface Water Classification Doc.
Mississippi R. / A1, B(WW-1), HH, C / 2/17/10 Surface Water Classification Doc.
Table 2: UAA Status
Stream / UAA Type(s) / Fieldwork Complete? / Recommended Designation(s) / StatusUnnamed Cr. / Recreational and
Aquatic / Yes / General Use to A2, B(WW-2) / General Use segment designation final. A2, B(WW-2) segment pending EPA approval.
Table 3: Impairment Status
Stream / Impairment(s)1 / TMDL Status / NotesUnnamed Cr. / None / N/A / Not monitored
Winnebago R. / Bacteria / Not scheduled / From confluence with Shell Rock R. extending upstream past confluence with Unnamed Cr.
Shell Rock R. / Bacteria / Not scheduled / From City of Shell Rock city limits upstream to Flood Cr.
Cedar R. / Bacteria/Biological/Nitrate / EPA Approved TMDLs for nitrate and bacteria / Biological impairment for mussels. Discharge present prior to TMDL approvals but no WLAs for Golden Grist assigned.
Iowa R. / Bacteria / Bacteria TMDL Development Scheduled for 2014 - 2015 / Impaired segment in Louisa County
Mississippi R. / Bacteria/Arsenic/
Aluminum / Not scheduled / Multiple downstream segments impaired
- Source: Final 2008 Impaired Waters List (EPA Approved)
Effluent Limitations
Table 4: Existing NPDES Permit Limits (Outfall 001)
Parameter / Concentration (mg/L) / Mass (lbs/d)7-d / 30-d / Max. day / 7-d / 30-d / Max. day
TSS / 30 / 45 / 125 / 188
pH (min. - max. std. units) / 6.5 / 9.0
TRC / 0.020 / 0.035 / 0.083 / 0.146
Iron / 1.0 / 1.0 / 4.17 / 4.17
Sulfate / 1,514 / 1,514 / 6,317 / 6,317
Due to considerations identified in the following section, no new effluent limits or changes to the existing effluent limits are expected to result from the proposed chemical switch.
POC Identification and Tier Protection Level
Chemical A and Chemical B both exhibit aquatic toxicity per the information provided in Appendix A. Neither Chemical A nor Chemical B contain any substances or result in any degradation products that alone or in combination with other substances present in the discharge would contribute to sludge deposits, floating debris, oil, grease, scum, objectionable odor, color, turbidity, or undesirable or nuisance aquatic life. Neither Chemical A nor Chemical B contain any elements or compounds included in Table 1 of Section 567 IAC 61.3(3) of the Iowa Administrative Code and do not have any known bioaccumulative, mutagenic, teratogenic or carcinogenic effects when introduced into the aquatic environment. In addition, neither Chemical A nor Chemical B or their degradation products alone or in combination with other substances present in the discharge or receiving waters produce additive or synergistic toxicity effects. Chemical A and Chemical B are equally biodegradable or persistent in the aquatic environment.
Therefore, the sole potential effect to the receiving stream’s water quality for both Chemical A and Chemical B is aquatic toxicity. Both the existing maximum concentration of Chemical A and the proposed maximum concentration of Chemical B are below ½ of the LC50 for the most sensitive species tested.
Chemical A is currently used and its presence in the discharge constitutes an existing water quality condition. Chemical B contains different compounds than Chemical A. Degradation within Iowa’s Antidegradation Implementation Procedure is defined as “A decline in the chemical, physical, or biological conditions of a surface water as measured on a pollutant-by-pollutant basis”. Pollutants of Concern are defined as “those pollutants which are reasonably expected to be present in the discharge and may reasonably be expected to negatively affect the beneficial uses of the receiving water”. Since Chemical B will be a new pollutant which is expected to be present in the discharge and has associated aquatic toxicity effects on laboratory test species its presence in the discharge would be considered degradation as defined in Iowa’s implementation procedure.
Table 5: Pollutants of Concern
POC / Secondary or WQBEL? / Beneficial Use Affected / TierChemical A / None / Aquatic life / 2
Chemical B / None / Aquatic life / 2
Identification & Discussion of Alternatives
Alt. No. 1: Land Disposal
Gilded Grist’s cooling tower operates on a continuous, year-round basis. Use of the blowdown wastewater for irrigation purposes or disposal via dedicated land application site(s) would be seasonal and dependent on climatic conditions. Therefore, any alternative utilizing land application as the sole means of blowdown disposal would require significant storage facilities in addition to land and irrigation equipment. Land application of blowdown wastewater would not eliminate the need for use of a scale & corrosion inhibitor and the estimated cost for this alternative is well in excess of the 115% economic efficiency criterion. Therefore, it is not a reasonable alternative as defined in Iowa’s implementation procedure.
Alt. No. 2: Zero Blowdown
Elimination of blowdown wastewater from an evaporative cooling system is possible but not practicable. Zero blowdown can be achieved when water loss from windage is equivalent to the blowdown rate using a high number of cycles of concentration. The high degree of concentration using this operational scheme requires special treatment of the cooling tower water using ion exchange softening or reverse osmosis, which would in turn generate additional concentrated wastewater residuals which are more difficult to dispose of and if discharged arguably more detrimental to the aquatic environment than the blowdown wastewater itself.
A dry cooling tower could be used in place of the existing evaporative cooling tower to achieve zero blowdown. However, this would require construction of a completely new cooling system for the facility. The existing evaporative cooling system is less than five years old with an expected remaining design life of at least 15 years provided that it is properly maintained. Replacement of the existing evaporative cooling system with a dry system is not practicable at this time, but may be considered at the end of the existing system’s useful life.
Alt. No. 3: Discontinue Use of Chemicals
Discontinuing the use of all scale & corrosion inhibitors is not a practicable alternative. Without use of a scale & corrosion inhibitor scale & corrosion products will foul the cooling system components, reducing the efficiency of the cooling tower and eventually cause total failure of the system. Control of scale and corrosion without chemical addition by electrical and/or ionization treatment of cooling water is currently marketed by at least one manufacturer. This treatment method may ultimately prove to be a viable method for controlling the chemistry of evaporative cooling systems without chemical addition. However, Gilded Grist believes that this technology is currently in an early stage of development and unproven in a similar application.
Alt. No. 4: Continue Use of Chemical A
Continued use of Chemical A is a practicable and affordable alternative, and is considered the Base Pollution Control Alternative (BPCA) in this analysis.
Alt. No. 5: Replace Chemical A with Chemical B
Gilded Grist believes that replacement of Chemical A with Chemical B will not only provide more effective scale & corrosion control, but will also improve the quality of the effluent and water quality in the receiving stream. This is the preferred alternative.
Table 6 summarizes the alternatives identified. Table 7 summarizes the evaluation of alternatives with respect to classification as non-degrading, less-degrading or the base pollution control alternative as well as the practicability, economic efficiency and affordability of each alternative.
Table 6: Alternatives and Present Worth Costs
Alt. No. / Description / Present Worth Cost11. / Land Disposal / $185,750
2. / Zero Blowdown / N/A
3. / Discontinue Use of Chemicals / N/A
4. / Continue Use of Chemical A / $65,750
5. / Replace Chemical A with Chemical B / $65,750
- The costs presented in this mock analysis are for illustrative purposes only. Actual costs for alternatives may vary. Present worth values are calculated using a discount rate of 4.125% (18 CFR 704.39 discount rate for 2011) and a 20-year design period.
Table 7: Alternative Classification and Evaluation
Alt. No. / BPCA, NDA or LDA? / Is the Alternative Reasonable?Practicable? / Economically Efficient? / % of BPCA / Affordable? / Reasonable?
1. / NDA / Yes / No / 283 / N/A / No
2. / NDA / No / N/A / N/A / N/A / No
3. / NDA / No / N/A / N/A / N/A / No
4. / BPCA1 / Yes / Yes / 100 / Yes / Yes
5. / LDA / Yes / Yes / 100 / Yes / Yes
- This alternative is also a non-degrading alternative since use of Chemical A is an existing water quality condition that pre-dates Iowa’s current Antidegradation policy.
Preferred Alternative
Alternative No. 5,Replacement of Chemical A with Chemical B, is thepreferredreasonable alternative. The BPCA (Alternative No. 4 - Continue Use of Chemical A) is technically a non-degrading alternative since its use is an existing water quality condition that pre-dates Iowa’s current Antidegradation policy. However, as noted previously the sole potential water quality effect to the receiving stream due to use of either Chemical A or Chemical B is aquatic toxicity. As shown in Appendix A, Chemical B will have lower toxicity than Chemical A at the proposed feed concentrations. Therefore, replacement of Chemical A with Chemical B will constitute an improvement in the water quality of the receiving stream and is considered the least degrading reasonable alternative.
Justification of Degradation
The preferred treatment alternative will result in degradation for one pollutant (Chemical B) but will at the same time remove an existing pollutant (Chemical A) and result in an overall water quality improvement. Alternatives which eliminate the discharge of both Chemical A and Chemical B were found to be not practicable or not economically efficient.
Since Iowa’s Antidegradation Implementation Procedures apply on a pollutant-by-pollutant basis and degradation will occur for one pollutant, the Social and Economic Importance (SEI) of the project must be demonstrated.
Project Social and Economic Importance
- Identify the affected community:
The City of Anywhere and surrounding rural areas are the directly affected community.
- Identify relevant factors that characterize the social and economic conditions of the affected community:
Gilded Grist’s facilities employ 40 people and purchase corn from the surrounding area. The facilities produce ethanol and distillers grains which are used as an alternative fuel source and animal feed product, respectively.
- Describe the important social and economic development associated with the project:
The selected alternative will ensure continued efficient operation of the facilities as well as the industry’s services to & investment in the City of Anywhere and surrounding areas.
Appendix A
Chemical Toxicity Information
Table A-1: Acute Toxicity
Chemical A / Chemical BDischarge concentration* / 1.0 - 2.0 mg/L / 2.0 - 3.0 mg/L
Species tested / Ceriodaphnia dubia
Test duration / 48 hr.
LC50 / 5.92 mg/L / >1,000 mg/L
Target Conc./LC50 / 0.17 / N/A
Max. Conc./LC50 / 0.34 / N/A
Species tested / Pimephales promelas
Test duration / 96 hr.
LC50 / 13.9 mg/L / >1,000 mg/L
Target Conc./LC50 / 0.07 / N/A
Max. Conc./LC50 / 0.14 / N/A
*Observed (Chemical A) and proposed (Chemical B) chemical concentrations within the cooling
water system. The lower value is the target concentration and the upper value is the maximum concentration. These are maximum potential discharge concentrations assuming that the cooling water system concentration is equal to the blowdown discharge concentration.
Table A-2: Chronic Toxicity
Chemical A / Chemical BDischarge concentration* / 1.0 - 2.0 mg/L / 2.0 - 3.0 mg/L
Species tested / Ceriodaphnia dubia
Test duration / 7-d
NOEC (reproduction) / 1.12 mg/L / 2.25 mg/L
Target Conc./NOEC / 0.89 / 0.89
Max. Conc./NOEC / 1.79 / 1.33
IC25 (reproduction) / 1.88 mg/L / 3.85 mg/L
Target Conc./IC25 / 0.53 / 0.52
Max. Conc./IC25 / 1.06 / 0.78
Species tested / Pimephales promelas
Test duration / 7-d
NOEC (mortality) / 3.11 mg/L / >1,000 mg/L
Target Conc./NOEC / 0.32 / N/A
Max. Conc./NOEC / 0.64 / N/A
IC25 (reproduction) / 6.69 mg/L / >1,000 mg/L
Target Conc./IC25 / 0.15 / N/A
Max. Conc./IC25 / 0.30 / N/A
*Observed (Chemical A) and proposed (Chemical B) chemical concentrations within the cooling
water system. The lower value is the target concentration and the upper value is the maximum concentration. These are maximum potential discharge concentrations assuming that the cooling water system concentration is equal to the blowdown discharge concentration.
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