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MEMORANDUM 

To: Amy Hambrick, U.S. EPA, Sector Policies and Programs Division/Natural 

Resources and Commerce Group 

From: Eastern Research Group, Inc. 

Date: January 2011 

Subject: Revised Estimation of Impacts for New Units Constructed Within Five 

Years After Promulgation of the SSI NSPS 

1.0 INTRODUCTION 

The U.S. Environmental Protection Agency (EPA), under section 129 of the Clean 

Air Act (CAA), is required to develop new source performance standards (NSPS) 

regulating emissions of nine pollutants from sewage sludge incineration (SSI) units: 

hydrogen chloride (HCl), carbon monoxide (CO), lead (Pb), cadmium (Cd), mercury (Hg), 

particulate matter (PM), total mass basis dioxins/furans (TMB PCDD/PCDF) and toxic 

equivalency basis dioxin/furans (TEQ PCDD/PCDF ), nitrogen oxides (NOx), and sulfur 

dioxide (SO2). This memorandum describes the estimation of cost and emission impacts 

of complying with the NSPS. Section 2.0 discusses the estimation of the number of new 

sources that may be constructed within five years after promulgation of the SSI NSPS. 

Section 3.0 discusses the methodology used to estimate cost and emissions reductions 

from complying with the maximum achievable control technology (MACT) floor level of 

control required in the NSPS, and Section 4.0 discusses control options more stringent 

than the MACT floor level of control. 

2.0 ESTIMATION OF NEW SOURCES 

Several significant changes have occurred to SSI units in the past 20 years. The 

U.S. EPA’s Office of Water (OW) set emission and discharge standards for sewage sludge 

disposal methods (including incineration) in 1993 (40 CFR part 503). As a result of the 

503 rule, many wastewater treatment facilities chose to use alternative methods for 

disposing of sewage sludge, such as landfilling or land application, rather than try to meet 

the incineration requirements. Many of the closed incinerators had been operated by 

municipalities or agencies serving smaller populations, i.e., less than 50,000 people.1 

The general trend has also been for facilities still incinerating sewage sludge to 

replace older multiple hearth (MH) units with newer fluidized bed (FB) units because of 

better emissions performance, savings in fuel cost, and flexibility in operation. Since 1988, 

there have been over 40 new FB systems installed, with 11 replacing existing MH units.2 

Discussions with the National Association of Clean Water Agencies (NACWA), the 
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industry trade group, indicated that only FB units are likely to be constructed in the 

future.3 Consequently, it was assumed that any new units that would be built after 

promulgation of the NSPS would be a FB design. 

In order to estimate the number of new sources that may be constructed in the five 

years following promulgation of the NSPS, the number of sources being constructed five 

years prior to proposal of the rule was reviewed to determine if there was a trend. Under 

EPA’s “New Source Review” (NSR) program, if a company is planning to build a new 

plant or modify an existing plant such that air pollution emissions will increase by a large 

amount, then the company must obtain an NSR permit. The NSR permit is a construction 

permit which requires the company to minimize air pollution emissions by changing the 

process to prevent air pollution and/or installing air pollution control equipment. The 

NSR program defines control levels based on the type of program the source is subject to: 

reasonably available control technology (RACT), best available control technology 

(BACT), or lowest achievable emissions reduction (LAER). Information from the EPA’s 

RACT/BACT/LAER database contains case-specific information on the “Best Available” 

air pollution technologies that have been required to reduce the emission of air pollutants 

from stationary sources. This information has been provided by State and local permitting 

agencies. The database was searched for sewage sludge incineration units permitted or 

constructed since 2005. The search results showed two fluidized bed (FB) units at the 

R.L. Sutton Water Reclamation facility in Georgia were permitted in 2005 and completed 

construction in 2008 and are currently in operation.4 Additional information collected 

from State environmental agencies and permits indicated an additional 3 units at the Mill 

Creek Wastewater Treatment Plant in Ohio were expected to finish construction and be in 

operation in 2010.5 All of these new FB units were replacements for MH units. 

Based on the data collected, and assuming the trend in construction continues, five 

additional FB units will be permitted to be constructed in five years after the NSPS is 

proposed. However, given the time necessary to review and assess the requirements of 

the NSPS and plan, permit, and construct incineration units, it is unlikely that all five 

would be in operation in the five years. For this analysis, it was assumed at least two new 

FB units would be constructed and in operation in this time period. 

3.0 METHODOLOGY USED TO ESTIMATE COST AND EMISSION 

REDUCTIONS OF THE MACT FLOOR LEVEL OF CONTROL 

Cost and emission reductions for new units complying with the NSPS were 

calculated by: (1) determining the controls that these units would most likely apply if the 

NSPS were not in place (referred to as the baseline level of control), (2) calculating the 

cost of complying with the NSPS emission levels, and (3) estimating the emissions 

reduction from complying with the NSPS emissions levels. Each of these steps is 

discussed in more detail. 
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3.1 Determining Baseline Controls

The baseline level of control that new units would likely implement (in the absence 

of the NSPS) was determined from reviewing the most common controls used at existing 

FB units, as shown in the SSI inventory memorandum1 and the database revisions 

memorandum.6 Table 3-1 shows the distribution of controls. Based on this information, 

the baseline controls assumed for the new units are a combination of venturi scrubbers and 

impingement scrubbers. Data gathered on the controls currently used at FB units indicates 

that few FB units operate an afterburner, because their CO emissions are already low. 

However, the analysis includes costs for afterburners because ACI/FF are needed for 

mercury control, and in order for these controls to operate effectively, an afterburner 

would need to be installed to keep moisture levels low (alternatively, a regenerative 

thermal oxidizer or waste-heat boiler could be used). In reality, new FB units that are 

constructed are likely to be designed to meet the CO level. Costing an afterburner 

provides a conservative estimate of costs. 

3.2 Calculating Baseline Emissions

The SSI baseline emissions memorandum7 documents the calculation of baseline 

emissions from existing FB SSI units. Baseline emissions are calculated on a mass basis 

by multiplying the concentration of the pollutant in the emission stream, flow rate of the 

emission stream, and the hours of operation of the SSI unit. For units where no emissions 

test data were collected, baseline emissions were generally estimated using an average 

uncontrolled concentration and applying reduction efficiencies associated with the control 

devices located at each SSI unit for each pollutant. Baseline concentrations used in the 

new source analysis are the same baseline emissions applied to fill data gaps for FB units 

having a venturi/impingement scrubber combination. 

A default flue gas flow rate was determined for FB units based on the average of 

known flow rate data for this subcategory. The data is described in further detail in the 

database revisions memorandum.6 Similarly, default values for sludge feed rates, unit 

capacities, and operational hours were determined by averaging the known data for these 

parameters for the FB subcategory. 

Table 3-2 shows the average concentration factors, average dry sludge capacity, 

and operating hours, as well as other default parameters necessary for the costs. These 

factors were applied to each new unit estimated to be constructed within the next five 

years. Table 3-3 shows the estimated baseline concentrations for new units. 

3.3 Calculating Costs and Emission Reductions

Costs were calculated using the procedures and algorithms discussed in the 

memorandum, “Revised Cost and Emissions Reduction of Complying with the MACT 

Floor for Existing SSI Units”.8 Control devices costed out were those that would be 
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necessary to meet the MACT floor level of control for new sources. Wet electrostatic 

precipitators (WESP) can be used for PM control; however, because an 

ACI/FF/afterburner combination was determined to be necessary for new sources to meet 

the NSPS limits for Hg and PCDD/PCDF, a FF was assumed to be sufficient for PM and 

lead control. Table 3-3 shows the comparison of baseline emissions levels to MACT floor 

levels to determine the amount of pollutant reduction needed and the types of control 

devices that would be used to meet the levels. Emission reductions from applying the 

MACT floor requirements to the baseline emission levels are presented in Table 3-3. The 

inputs to the cost algorithm are presented in Table 3-2. 

Table 3-4 shows the estimated total capital investment (TCI) and total annual costs 

(TAC) calculated for a single unit using the cost algorithms previously discussed. The 

table also shows the monitoring, testing, reporting, and recordkeeping costs. The table 

shows the TCI and TAC for the two new FB units that are assumed to be constructed and 

in operation in the five years after proposal of the NSPS. Table 3-5 shows the detailed 

capital and annual costs of continuous CO emissions monitoring for each new SSI unit 

(continuous CO emissions monitoring costs were not presented in the “Cost and 

Emissions Reduction of Complying with the MACT Floor for Existing SSI Units” 

memorandum because it was an alternative monitoring requirement and not required). 

4.0 ANALYSIS OF BEYOND THE FLOOR OPTIONS 

The control technologies costed to achieve the MACT floor levels are generally 

the most effective controls available: fabric filters for PM, Cd, Pb; activated carbon 

injection with fabric filters and afterburners/RTO for Hg and PCDD/PCDF; afterburners 

for CO; and packed bed scrubbers for HCl and SO2. In addition, incremental additions of 

activated carbon have not been proven to achieve further reductions above the projected 

flue gas concentration estimated to achieve the limits for new sources. Data gathered 

does not indicate that any FB units operate NOx controls, such as selective noncatalytic 

reduction, selection catalytic reduction, or flue gas recirculation because the NOx

emissions are already low. To meet the NSPS NOx limit SNCR costs were calculated. In 

reality, new FB units that are constructed are likely to be designed to meet the NOx level 

using low NOx burners. Costing an SNCR provides a conservative estimate of costs. No 

beyond the floor options were analyzed for this analysis because we are not aware of any 

technologies or methods to achieve emission limits more stringent than the MACT floor 

limits for new units, which are based on the lowest emitting FB units. 

5.0 REFERENCES 

1. Inventory Database for the Sewage Sludge Incineration Source Category. 

Memorandum from Eastern Research Group to Amy Hambrick, U.S. 

Environmental Protection Agency. June 2010. 

2. A Comparison of Fluid Bed and Multiple Hearth Biosolids Incineration. Ky 

Dangtran, John Mullen, and Dale Mayrose. Paper presented at the 14th Annual 
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Residuals and Sludge Management Conference. February 27-March 1, 2000, 

Boston MA. 

3. Meeting minutes from Sewage Sludge Incinerator Informational Meeting with the 

National Association of Clean Water Agencies (NACWA). Research Triangle 

Park, NC. August 25, 2009 

4. R.L. Sutton Water Reclamation Wastewater Treatment permit # 4953-067-0018-V01-1 RACT/BACT/LAER Clearinghouse. http://cfpub.epa.gov/rblc/

5. Mill Creek Wastewater Treatment Plant. Final permit to install. Permit 

Application #14-05837. 

6. Post-Proposal SSI Database Revisions and Data Gap Filling Methodology. 

Memorandum from Eastern Research Group, Inc. to Amy Hambrick, U.S. 

Environmental Protection Agency. January 2011. 

7. Revised Estimation of Baseline Emissions From Existing Sewage Sludge 

Incineration Units. Memorandum from Eastern Research Group to Amy 

Hambrick, U.S. Environmental Protection Agency. January 2011. 

8. Revised Cost and Emissions Reduction of Complying with the MACT Floor for 

Existing SSI Units. Memorandum from Eastern Research Group to Amy 

Hambrick, U.S. Environmental Protection Agency. January 2011.