Document ID: EPA-HQ-OW-2009-0819-5622
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2015-11-03T05:00Z

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

TO:	Steam Electric Rulemaking Record

FROM:	 Danielle Lewis, ERG
	Anna Dimling, ERG

DATE:	September 30, 2015

SUBJECT:	Evaluation of Chemical Precipitation Costs for Ash Transport Water

	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. As part of this technical support, EPA, with support from ERG, evaluated chemical precipitation as a potential basis for a technology option for the treatment of fly ash transport water and bottom ash transport water.  Based on EPA's analysis, described below, EPA found costs for chemical precipitation treatment of fly ash and bottom ash transport water to be comparable or higher than the cost for converting to dry handling or closed loop technologies. Additionally, the chemical precipitation technology removes fewer pollutants compared to conversion to dry handling; therefore, EPA did not include chemical precipitation treatment as part of the regulatory options (see Section 8 of the Technical Development Document for the Final Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source Category (EPA-821-R15-007) for more details on the regulatory options).  This memorandum describes the methodology EPA used to estimate capital costs to install a chemical precipitation system for the treatment of fly ash transport water and bottom ash transport water, and a comparison of chemical precipitation treatment system capital costs to estimated capital costs for the dry handling or closed-loop technologies.

	For this evaluation, EPA used the chemical precipitation cost module along with generating unit-level discharge flow rates for fly ash transport water and bottom ash transport water to estimate plant-level capital costs to install a chemical precipitation treatment system. EPA included the following pieces of equipment in the chemical precipitation design basis:

   * Pumps.
   * Tanks (e.g., reaction tanks, holding tanks).
   * Chemical feed systems for the addition of lime, organosulfide, ferric chloride, and polymers.
   * Mixers. 
   * Clarifiers.
   * Filter presses.
   * Sand filters.
   * Mercury analyzer.

 For each piece of equipment, EPA obtained cost information from vendors for various sizes of the equipment (e.g., flow, volume). Then EPA related all of these to an associated flow rate using information based on the technology design basis (e.g., tank volume related to flow by design residence time). EPA then used the cost and flow information to generate an equation that could estimate the costs for any steam electric power plant wastewater flow rate.
	The chemical precipitation cost module, as described in the Incremental Costs and Pollutant Removals for the Final Effluent Limitation Guidelines and Standards for the Steam Electric Generating Point Source Category ("Costs and Loads Report"; DCN SE05831), is the same cost module used to estimate costs associated with chemical precipitation systems used to treat flue gas desulfurization (FGD) wastewater.  As described in Section 6.1 of the Costs and Loads Report, the chemical precipitation cost module estimates capital and operation and maintenance (O&M) costs to install and operate a chemical precipitation system specifically designed and operated to treat steam electric power plant wastewater. To estimate the capital costs associated with the treatment of fly ash transport water and bottom ash transport water, EPA summed the capital cost output elements, including purchased equipment (with the exception of the equalization tank), direct capital costs, and indirect capital costs,  from the cost module for the purposes of this cost analysis.  EPA excluded capital costs associated with equalization tanks (See Section 6.1.6.3 of DCN SE05831) because EPA believes plants would be likely to continue operating existing ash settling impoundments instead of installing large holding tanks for equalization.  EPA used the same residence time and other equipment sizing bases as described in the Costs and Loads Report to cost chemical precipitation for FGD wastewater.
	
	EPA estimated plant-level capital costs for each plant discharging fly ash, bottom ash, or combined ash transport water to treat these wastestreams with a chemical precipitation system. Cost estimates reflect separate treatment system costs for the treatment of fly ash transport water and bottom ash transport water. EPA used discharge flow rates from the "Ash Transport Water Input Table" (See Section 4.1.2 of DCN SE05831), which is the basis for the ash transport water loadings calculations.  For plants with ash transport water flows identified as combined ash sluice, EPA used responses from the Questionnaire for the Steam Electric Power Generating Effluent Guidelines (DCN SE05903) to separate the flow into contributions from fly ash sluice and bottom ash sluice using the unit flow fraction consistent with the methodology used to develop the "Ash Transport Water Input Table" (See Section 4.1.2.3 of DCN SE05831).  To allow EPA to compare the cost of chemical precipitation treatment to the dry/closed-loop ash handling technologies, EPA then identified which plants discharge ash transport water (fly ash or bottom ash) and incur costs for dry ash handling or closed-loop systems for use in this analysis. EPA identified 16 plants discharging fly ash transport water and 95 plants discharging bottom ash transport water and incurring dry ash handling costs. Tables A-1 and A-2, included as attachments to this memorandum, include the plant-level discharge flow rates used to estimate the costs associated with a chemical precipitation treatment system for fly ash transport water and bottom ash transport water, respectively. 
	
	For the 16 plants included in this analysis that discharge fly ash transport water, EPA estimated a total capital cost of $2.3 billion to install chemical precipitation systems.  For the 95 plants included in this analysis that discharge bottom ash transport water, EPA estimated a total capital cost of $6.7 billion to install chemical precipitation systems. Tables A-1 and A-2 include the plant-level cost estimates.

	EPA compared the capital costs estimated for the chemical precipitation systems to the capital cost estimated for the dry ash handling or closed loop ash handling system on a plant-level.  Plant-level capital costs for dry handling or closed loop ash handling systems are included in Tables A-1 and A-2.  For the 16 plants discharging fly ash transport water, chemical precipitation treatment systems capital costs are almost 17 times more expensive than dry handling on an industry-level.  For the 95 plants discharging bottom ash transport water, chemical precipitation systems capital costs are almost two times more expensive than dry handling or closed loop systems on an industry-level. Because the costs for chemical precipitation treatment of fly ash and bottom ash transport water were found to be higher than the cost for converting to dry handling or closed loop technologies, and the chemical precipitation treatment removes fewer pollutants, EPA did not include this treatment technology as part of the regulatory options.