“Second Generation” ATAD – A-TAD Better? – Two Case Studies of Conversion From “First Generation” to “Second Generation” ATAD Systems

Autothermal Thermophilic Aerobic Digestion (ATAD) is becoming more prevalent due to its advantages over conventional aerobic digestion, including the generation of a Class “A” product, a relatively small footprint, and reduced biosolids for end disposal.Both the Grand Chute-Menasha West Wastewater Treatment Facility (WWTF) in Neenah, Wisconsin and the Edwards Wastewater Treatment Plant (WWTP) operated by the Eagle River Water and Sanitation District located in Edwards, Colorado have “First Generation” ATAD systems and are in the process of converting the systems to “Second Generation” ATAD systems.The “Second Generation” ATAD systems include process modifications over the “First Generation” ATAD systems such as better mixing and process control that have resulted in higher volatile solids reduction, lower product volume, less odor generation and less sidestream impacts at several installations. This paper explores the advantages of the “Second Generation” ATAD systems over the original installations and the reasons why the two plants decided to convert their systems to the newer ATAD systems.