The Township and City of Ypsilanti, Michigan, sits outside the Detroit metropolitan area. When the Ypsilanti Community Utilities Authority (YCUA) needed to replace its multiple hearth biosolids incinerator, it turned to Tetra Tech. New air toxics rules from Michigan and the U.S. Environmental Protection Agency (EPA) warranted additional pollution control measures beyond conventional scrubbing for new incinerator installations. Tetra Tech’s solution was a fluidized bed biosolids incinerator system with an activated carbon filter—the first of its kind in the nation. The result is the cleanest burning, most advanced municipal biosolids incinerator system in the country.

Future installations will have to meet or surpass the bar set by this project, which included a fluidized bed incinerator with a four-step emissions control system consisting of the following:

  • Venturi scrubber
  • Impingement tray scrubbers
  • Wet electrostatic precipitator
  • Granular-activated carbon adsorbers (the first municipal application in the country)

Tetra Tech addressed several unique issues during the study and design phases, including expanding the service area and increasing capacity; the YCUA Board’s directive that the new facility should exemplify the community’s environmental leadership; and that the Michigan Department of Environmental Quality’s air quality requirements are more stringent than those of the EPA.

Tetra Tech worked with more than 20 YCUA wastewater treatment plant personnel including representation from operations, mechanical, information technology, laboratory, health and safety, and executive administrators to determine the most viable biosolids management alternative. Over a four-month period, the project team took field trips and held special meetings to evaluate the management alternatives of landfilling, pelletization, land application, lime-stabilized agricultural reuse, composting, and incineration.

Because of Tetra Tech’s commitment to sustainability and our experience with regulatory consulting, we addressed these challenges through an innovative design using the latest technologies and processes.

Performance testing revealed that system emissions were cleaner than the air permit requirements dictated. Despite handling 60 percent more biosolids daily than the previous incinerator, this state-of-the-art system resulted in a net reduction of emissions, contributing to improved air quality in the community and setting a new nationwide standard.


The YCUA Biosolids Incinerator Project won an American Council of Engineering Companies National Honor award in 2007.