Variability in THC, CO & NOx Emissions from SSIs 

Robert Dominak 

to: 

Amy Hambrick 

05/20/2010 11:37 AM 

Cc: 

RSCHMIDT, Michael Galbraith, Maria Gomez-Taylor, Ron Myers, Ketan Patel, Suzanne Rudzinski, 

Rick Stevens, "Mark Feltner", "Dave Taylor", akrantz, CHornback, kjones 

Hi Amy, 

The following is a summary of the items that we discussed during our recent telephone conversations: 

1. Carbon monoxide (CO) emissions are substantially lower from fluidized bed incinerators than multiple 

hearth incinerators, due to their configuration. 

2. Under the Part 503 Regulation, total hydrocarbon (THC) emissions are a surrogate for all potentially toxic 

compounds emissions, including dioxins. 

3. POTWs located in New Jersey that practice incineration were subject to a CO limit of 100 ppm prior to 

the promulgation of the Part 503 Regulation's 100 ppm THC limit. As a result, U.S. EPA allowed all POTWs 

that practice incineration to use an alternate CO limit of 100 ppm on a monthly average basis in lieu of a 

THC of 100 ppm on a monthly average basis. 

4. A CO Limit of 100 ppm is substantially more stringent than a THC limit of 100 ppm. For example, an SSI 

with THC emissions of 20 ppm could have CO emissions of 3,000 ppm. 

5. NOx and CO emissions from SSIs are inversely proportional. 

6. NOx and THC emissions from SSI are inversely proportional. 

Given the complexity of these issues, I pulled from my files a 1997 report that Pacific Environmental 

Services prepared for U.S. EPA titled "An Investigation of Alternative Means for Demonstrating Compliance 

with the Part 503 Total Hydrocarbon Operational Standards", and a 1999 Water Environment Research 

Foundation (WERF) report titled "Evaluating and Measuring Biosolids Incinerator Emissions." 

The following is a summary of the pertinent items contained within these reports: 

Pacific Environmental Services Study 

The main purpose of the Pacific Environmental study was to determine if there was a relationship between 

concentrations of THC and CO in SSI exhaust gases, so that CO monitors (which are easier to operate and 

maintain) could be used in lieu of THC monitors to demonstrate compliance with the Part 503 Regulation's 

monthly THC limit. 

The study mainly focused on multiple hearth incinerators located in Arlington VA and Cleveland OH, and a 

fluidized bed incinerator located in Huntington West VA. In addition, data was obtained from 6 other POTWs 

that have multiple hearth incinerators. 

The PES study did not find a detailed enough correlation between THC and CO and noted that SSI 

operating parameters (e.g., feed rate, moisture content of the sewage sludge, heat value of the sewage 

sludge, etc.) affect the concentrations of both THC and CO in exhaust gases. As a result, EPA decided not 

to allow CO monitors to be used in lieu of THC monitor, where a POTW is demonstrating compliance with 

THC limit of 100 ppm. 
Below are five scanned pages from the PES Report (i.e., the cover page and four graphs). The graphs 

clearly demonstrate that THC and CO are related, but that the relationship varies from Plant to Plant, having 

many variables that can impact the emissions. 

Water Environment Research Foundation Study 

The main purpose of the WERF Study was to address present and future emission concerns for POTWs 

that operate multiple hearth incinerators. 

The primary findings of the study were as follows: 

1.The team reviewed more than 153 NOx emission tests that were conducted on 24 multiple hearth 

incinerators and found that NOx emissions from multiple hearth incinerators vary from 3 lbs/dry ton to 14 

lbs/dry ton 

2. NOx emissions increased as the top hearth or afterburner temperature increased. 

3. NOx emissions increase with oxygen content. 

4. NOx and THC Emissions are inversely proportional. 

5. NOx and CO emissions are inversely proportional. 

6. CO emissions are substantially higher than THC emissions. 

7. Both THC and CO emissions decrease with temperature, while NOx emissions increase. 

Attached are five scanned pages from the WERF report (i.e., the cover page and four graphs.) 

Please do not hesitate to contact me if you have any questions concerning the attached graphs, or if you 

need additional information concerning THC, CO and NOx emissions from SSIs. 

Thanks, 

Bob Dominak 

Co-Chair NACWA Biosolids Management Committee 

Residuals & Air Emissions Manager 

Northeast Ohio Regional Sewer District 

3900 Euclid Avenue 

Cleveland, OH 44134 

Phone: 216-881-6600 ext. 6405 

E-Mail: dominakr@neorsd.org 






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f,,'uaffng and Measuring Biasolids Inanerator Emis

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fWJIlJDIing and Measuring Biosalid, Indnerator Emissions 2·27