NACWA Letter to M. Hale 

June 2, 2009 

Page 1 

EXECUTIVE COMMITTEE

PRESIDENT

Marian A. Orfeo

Director of Planning 

& Coordination

Massachusetts Water 

Resources Authority

Boston, MA

VICE PRESIDENT

Kevin L. Shafer

Executive Director

Milwaukee Metropolitan 

Sewerage District

Milwaukee, WI 

TREASURER

Jeff Theerman

Executive Director

Metropolitan St. Louis

Sewer District

Saint Louis, MO

SECRETARY

David R. Williams

Director of Wastewater

East Bay Municipal 

Utility District

Oakland, CA

PAST PRESIDENT

Christopher M. Westhoff

Assistant City Attorney 

Public Works General Counsel

City of Los Angeles

Los Angeles, CA

EXECUTIVE DIRECTOR

Ken Kirk

June 2, 2009 

Matt Hale 

Director, Office of Resource Conservation and Recovery 

U.S. Environmental Protection Agency, Ariel Rios Building 

1200 Pennsylvania Avenue, N. W. Mail Code: Mail Code: 5301P 

Washington, DC 20460 

Via Electronic Mail: hale.matt@epa.gov 

Dear Matt, 

Thank you again for taking time to meet with NACWA to discuss your office’s efforts 

to develop a definition of solid waste for Clean Air Act regulatory purposes. As we 

outlined during the meeting and in our February 2 comments, we believe the 

regulatory status of sewage sludge (biosolids) is clear – it is expressly exempted by the 

RCRA statutory definition of solid waste as ‘solid and dissolved materials in 

domestic sewage.’ Congress considered the potential overlap in authority over 

biosolids and chose to comprehensively regulate biosolids under the Clean Water 

Act. EPA’s many rulemakings regarding the definition of solid waste have 

consistently recognized this Congressional mandate.

NACWA understands that the EPA Office of Air and Radiation is developing 

regulations for solid waste incineration units under Section 129 of the Clean Air Act. 

By clarifying that sewage sludge is excluded from the definition of “solid waste” by 

the domestic sewage exclusion, EPA is acknowledging that it must regulate sewage 

sludge incinerators (SSIs) under Section 112 instead of Section 129. This will help 

ensure that incineration remains one of the five available options for biosolids 

management. 

For many years, NACWA has been supporting EPA’s efforts to develop SSI 

regulations under Section 112 of the Clean Air Act. NACWA helped EPA update its 

database so that it included the significant emission reductions achieved by the Part 

503 regulations of SSIs under the Clean Water Act. We have attached a description of 

the data provided by NACWA in response to EPA’s initial estimates of the SSI 

contribution of certain compounds in urban areas regulated under Section 112(k). It 

is our understanding that these corrections and updates resulted in EPA concluding 

that SSIs were not major sources of hazardous air pollutants and that they provided a 

far smaller percent contribution than originally estimated by EPA. 
NACWA Letter to M. Hale 

June 2, 2009 

Page 2 

As area sources regulated under Section 112(k) of the Clean Air Act, NACWA members can be allies in EPA’s 

effort to address risks in urban areas. NACWA members have unique authorities under the Clean Water Act to 

regulate the discharges of non-domestic users of the sewer system. POTW indirect discharge permits can be 

used to reduce the concentration of compounds of concern in the sewage sludge and reduce the amount of

these compounds that may be emitted into the urban environment. On the other hand, the unpredictable 

nature of the domestic sewage contribution would make it virtually impossible for a POTW to simultaneously 

meet all of the established MACT limits for emissions regulated under Section 129. 

We believe that the best way to ensure SSIs are properly regulated under Section 112 is to include in the 

regulatory definition of solid waste now under development an express exclusion for domestic sewage and the 

sludge generated from the processing of domestic sewage. NACWA believes that the scope of the exclusion is 

clear and the existing Part 503 regulations supplemented with targeted reductions under Section 112(k) provide 

a sound basis for comprehensive biosolids regulation. 

Again, thank you and your staff for meeting with us. Please do not hesitate to contact me if you need additional 

information about SSIs or would like to discuss the issue further. 

Sincerely, 

Chris Hornback 

Senior Director, Regulatory Affairs 

ATTACHMENT 

cc: Robert Dominak, Northeast Ohio Regional Sewer District 

 Robert Wayland, USEPA 

 Rick Stevens, USEPA 
Sewage Sludge (Biosolids) Incinerators (SSIs) Percentage Contribution

to each of the 30 urban HAPs regulated under Section 112 of the CAA

A. 1,1,2,2-Tetrachloroethane

 EPA SSI Emission Estimate - 6% of total 

Concentrations of 1,1,2,2 - Tetrachloroethane in analyzed biosolids were below the detection limit of 0.52 mg/dry kg.

Give the high exhaust gas temperatures for SSIs (1200 -1400°F for Multiple Hearth Incinerators and 1500 -1600°F for Fluidized Bed Incinerators) 

and very low Total Hydrocarbon emissions (0 - 50 ppm), emissions of 1,1,2,2 -Tetrachloroethane from SSI are negligible.

B. Acrylonitrile

 EPA SSI Emission Estimate - 3% of total

Concentrations of Acrylonitrile in analyzed biosolids were below the detection limit of 0.011 mg/dry kg.

Give the high exhaust gas temperatures for SSIs (1200 -1400°F for Multiple Hearth Incinerators and 1500 -1600°F for Fluidized Bed Incinerators) 

and very low Total Hydrocarbon emissions (0 - 50 ppm), emissions of Acrylonitrile from SSIs are negligible.

C. Arsenic Compounds

 EPA SSI Emission Estimate - 2% of Total

Emissions of Arsenic from SSIs are regulated under 40 CFR Part 503 (Use or Disposal of Sewage Sludge).

Through the use of venturi/impingement tray scrubbing systems and controlling burning zone temperatures, arsenic emissions

are normally less than 1% of the arsenic concentrations in the sewage sludge. A survey of 20 NACWA member POTWs 

that practice incineration revealed average emissions of 0.0019 tons/year in 2002. 

D. Cadmium Compounds

 EPA SSI Emission Estimate - 11% of total

Emissions of Cadmium from SSIs are regulated under 40 CFR Part 503 (Use or Disposal of Sewage Sludge).

Through the use of venturi/impingement tray scrubbing systems and controlling burning zone temperatures, cadmium emissions

are normally less than 1% of the cadmium concentrations in the sewage sludge. A survey of 16 NACWA member POTWs 

revealed total cadmium emissions in 2000 of 0.28 tons, while EPA had estimated cadmium emissions from these 16 POTWs to 

be 4.08 tons per year. The reduction in cadmium emissions are also due to EPA's Pretreatment Program.
E. Chloroform

 EPA SSI Emission Estimate - 0%

NACWA agrees with EPA's SSI emission estimate for chloroform.

F. Chromium Compounds

 EPA SSI Emission Estimate - 1%

Emissions of Chromium from SSIs are regulated under 40 CFR Part 503 (Use or Disposal of Sewage Sludge).

Through the use of venturi/impingement tray scrubbing systems and controlling burning zone temperatures, chromium emissions

are normally less than 1% of the chromium concentrations in the sewage sludge. A survey of 20 NACWA member POTWs 

revealed average cadmium emissions in 2002 of 0.0033 tons per POTW. The negligible chromium emissions are also due to 

EPA's Pretreatment Program.

G. Dioxins (2,3,7,8 - TCDD)

 EPA SSI Emission Estimate - 5% 

In a 1994 report, U.S. EPA estimated that the SSIs in the U.S. emitted a total of 23 grams TEQ (Dioxin) to the atmosphere each year. 

This was approximately 0.25% of total Dioxin emissions. A study conducted by NACWA/Cambridge Environmental revealed that that actual

total emissions was 8 grams per year and that SSIs were a negligible source of dioxins.

H. Lead Compounds

 EPA SSI Emission Estimate - 7%

Emissions of Lead from SSIs are regulated under 40 CFR Part 503 (Use or Disposal of Sewage Sludge).

Through the use of venturi/impingement tray scrubbing systems and controlling burning zone temperatures, lead emissions

are normally less than 1% of the lead concentrations in the sewage sludge. A survey of 20 NACWA member POTWs 

revealed average cadmium emissions in 2002 of 0.0222 tons per POTW. The negligible lead emissions are also due to 

the use of unleaded gasoline.

I. Manganese Compounds

 EPA SSI Emission Estimate - 0%

NACWA agrees with EPA's SSI emission estimate for manganese.
J. Mercury Compounds

 EPA SSI Emission Estimate - 3%

The 230 biosolids incinerators located in the United States are a very minor source of mercury. For example.

conservative (high) estimates show these units collectively emit less than 0.9 metric tons (1 U.S. ton) of mercury to the atmosphere each year,

which is roughly 0.5% of the total amount of mercury annually emitted to the atmosphere in North America. 

POTWs that practice incineration are subject to the National Emission Standards for Hazardous Pollutants (NESHAPs) standard of 3,200 grams mercury 

per 24-hours as a plant-wide ceiling. Actual mercury emissions from each of these POTWs are less than 200 grams in 24-hours. This is primarily due to 

the fact that mercury concentrations in biosolids are typically less than 1 mg mercury /dry kg. Applying these results to available emission inventory 

estmiates would reduce the stated impact of biosolids incinerators even more.

K. Nickel Compounds

 EPA SSI Emission Estimate - 1%

Emissions of Nickel from SSIs are regulated under 40 CFR Part 503 (Use or Disposal of Sewage Sludge).

Through the use of venturi/impingement tray scrubbing systems and controlling burning zone temperatures, nickel emissions

are normally less than 1% of the chromium concentrations in the sewage sludge. The negligible nickel emissions are also due to 

EPA's Pretreatment Program.

L. Polychlorinated Biphenyls

 EPA SSI Emissions Estimate - 18%

Testing of sewage sludge for PCBs revealed concentrations below the detection limits. This is due to the banning the manufacturer and use

of PCBs in the 1970s. In addition, due to the high temperatures within an incinerators (1400 -1600°F), any PCBs that could possibly end up 

in sewage sludge would be destroyed during the incineration process.

M. Vinyl Chloride

 EPA SSI Emissions Estimate - 1%

Testing of sewage sludge for vinyl chloride revealed concentrations below the detection limits. 

RPD

6-1-09