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.
Memorandum

September 1, 2015

Page 2

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.

1

 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.2

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.3Tables A-1 and A-2, included as 

attachments to this memorandum, include the plant-level discharge flow rates used to estimate 

 

1 The cost of equalization tanks is small. Even if a plant decided an equalization tank was needed, it would increase 

the capital costs by only two to three percent. 

2 EPA estimated chemical precipitation costs for those plants identified as discharging fly ash transport water or 

bottom ash transport water after adjusting the population for the Coal Combustion Residual (CCR) rule and the 

Clean Power Plan and excluding oil-fired and small generating units.

3 EPA excluded plants with only a pollutant loading or only a compliance cost (e.g., only pollutant loadings are 

estimated for plants that handle fly ash wet and dry but have capacity to handle all ash dry; only costs were 

estimated for plants that recycle bottom ash). 
Memorandum

September 1, 2015

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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 plantlevel. 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.