New Source Performance Standards (NSPS) and Emissions Guidelines for Sewage Sludge Incineration (SSI) Units

Stack Testing for Air Quality ControlHistory of NSPS and Emissions Guidelines for SSI Units

On Feburary 21, 2011, the Environmental Protection Agency finalized new source performance standards (NSPS) and emissions guidelines for new and existing sewage sludge incineration (SSI) units. The rule, per the EPA research is expected to impact 204 units currently in operation. This rule is one of the many new standards for units that emit pollutants under the MACT (Maximum Achievable Control Technology) Standards, and was enacted under Section 129 of the Clean Air Act (See also: New RICE Rules for MACT Standards and Compliance.)

The purpose of the rule is to reduce emissions of a number of toxic air pollutants, also known as hazardous air pollutants, that are known or suspected of causing cancer and other serious health benefits.

On April 27, 2012, the EPA issued a Denial of Reconsideration Petitions for the Final Rule.

Affected SSI Units

An SSI unit is an incinerator or combustion device that is used to burn dewatered sewage sludge. The units are typically owned by municipalities, and located at wastewater treatment facilities. They come in two primary types. The first – Multiple Hearth – covers over 80 percent of the identified SSI units. The other units are Fluidized Bed combustors. Most of the affected units are in the Eastern parts of the United States, with the largest number of facilities in New York, Pennsylvania, and Michigan. There are a significant number on the West Coast as well. Units incinerating sludge at other types of facilities, such as commercial, industrial, and institutional, will be covered under different air pollution incineration standards.

Sewage Sludge Treatment Plants are regulated under 40 CFR Part 60, Subpart O, as well as 40 CFR Part 61, Subparts C and E. The new source performance standards for these units have been promulgated under Subpart LLLL, and the Emission Guidelines themselves are promulgated under Subpart MMMM. The EPA estimates that of the 204 active SSI units, 155 are currently meeting these emission limits, and forty will need to install one or more air pollution control device.

Regulated Pollutants for SSI

The following table lists the Regulated Pollutant, the unit of measurement for emission limits, and the Emission Limit itself for both Multiple Hearth and Fluidized Bed Incinerators.



Emission Limit for MH Incinerators

Emission Limit for FB Incinerators


mg/DSCM @7% O2



Carbon Monixde

ppmvd @7% O2




ppmvd @7% O2




mg/DSCM @7% O2



Oxides of Nitrogen

ppmvd @7% O2




mg/DSCM @7% O2



Dioxins/Furans, Total Equivalency Quality

ng/dscm @7% O2 (TEQ)



Dioxins/Furans, Total Mass Basis

ng/dscm @7% O2 (TMB)



Particulate Matter

mg/DSCM @7% O2



Sulfur Dioxide

ppmvd @7% O2




Measuring Emissions

To measure and quantify the emission rates for these pollutants, it is typically necessary to do an Emissions Sampling Program, or Stack Test, conducted by a qualified and accredited stack testing organization. The EPA has reference methods for quantifying emissions for each regulated pollutant, and the testing must be done in accordance with those methods. The methods in question can be found on the EPA website.

Mercury Emissions and the Ontario Hydro Method

Mercury (Hg) is one of the strictly regulated pollutants. Mercury has been shown through research to adversely affect developing brains in children, including detrimental effects on IQ, learning, and memory. However, controlling mercury emissions can be tricky, dependent on what form the Mercury takes in the emission from the stack. There are two primary types: Oxidized and Particle-Bound, and the control devices associated with controlling those two types are different. For that reason, during stack testing to determine existing emissions, many owners of SSI units elect to perform a special Mercury Speciation test, utilizing ASTM Ontario Hydro Method. The data taken from this sampling can be used to determine the best approach to further controlling emissions for that specific stack.

Sludge and Scrubber Water Analysis

Many facilities often undertake fuel analysis on the sludge feedstock itself, to determine the base level of pollutants in the sludge prior to being incinerated. These measurements can be utilized to determine the current effectiveness of emissions controls.

About Environmental Source Samplers, Inc. (ESS)

ESS has some of the most experienced SSI test crews in the country. In the last six months, ESS has conducted this nearly identical test series for SSIs at multiple municipal facilities in Virginia, Ohio, and New York.  All test series have been completed on-time and on budget. ESS has a history of working with chief WWTP consultants that extends back to 1990, and has partnered with some of the leading experts on SSI in the nation. Our experience in some of the more exacting methodologies required by the SSI test program is unsurpassed in this industry.

Brian Mellor About Brian Mellor

Brian Mellor works with Environmental Source Samplers, Inc. (ESS), an environmental consulting firm specializing in stack testing, CEMS Testing, and EPA air emissions compliance.

ESS has conducted international stack testing projects at Johnson Atoll, in the Philippines, the Dominican Republic, Hong Kong, and various parts of Europe. If you need a team that will do your international job with efficiency and effectiveness, call ESS at (910) 799-1055 or visit