A federal appeals court has remanded portions of the Environmental Protection Agency’s 2011 sewage-sludge incinerator rule to the agency for further review but left the current maximum achievable control-technology air-emission limits in place.

At issue in the case was EPA’s methodology for setting new limits for emissions from new and existing sewage-sludge incineration (SSI) units at wastewater treatment plants. 

The new limits require numerous wastewater treatment plants that have SSI units to add costly air-emission controls, says Nathan Gardner-Andrews, general counsel for the National Association of Clean Water Agencies (NACWA).

At the time the rules were finalized in February 2011, EPA said about 40 of the 204 SSI units operating in the U.S. would need to install one or more devices for air pollution control and that two new SSI units could be built within the following five years.

The final rule set new emission guidelines for two SSI categories: multiple hearth and fluidized bed. The rule established limits for nine pollutants emitted from the regulated SSI units: mercury, lead, cadmium, hydrogen chloride, particulate matter, carbon monoxide, dioxins/furans, nitrogen oxides and sulfur dioxide.

NACWA and the Sierra Club each challenged the 2011 rule in court, although for different reasons.

They both contended that EPA’s methodology in collecting data on pollutants emitted by SSI’s was flawed. But the Sierra Club argued that it would like to see stronger emissions limits in place. NACWA contended that a more comprehensive EPA survey and analysis would show that less stringent emissions limits are needed.

EPA surveyed SSI units at only nine municipalities and supplemented those results with numbers from state environmental agencies’ public databases.

In its Aug. 20 ruling, a three-judge panel of the U.S. Circuit Court of Appeals for the District of Columbia concluded, “We agree that in some respects EPA has not adequately established that its estimations are reasonable, and so remand parts of the sewage sludge incinerator rule to EPA for further proceedings without vacating the current standards.”

Ken Kirk, NACWA executive director, said in a statement that the remand “is a clear statement that EPA’s technical justifications for the rule are inadequate …. As a result of [the] decision, EPA must go back and get these SSI emission limits right.