Largest Municipal ATAD — Class A Biosolids at Middletown WWTP

The City of Middletown, Ohio owns and operates a conventional activated sludge wastewater treatment plant (WWTP). The former biosolids management plan at Middletown consisted of lime stabilization and land application of the biosolids. The Middletown lime stabilization system produced Class B biosolids that were stockpiled outside on an uncovered, concrete pad enroute to land application at nearby farmlands.Faced with excessive odor complaints, looming regulatory action, and an overall concern with the long-term viability of its existing biosolids management plan, the City of Middletown commissioned a biosolids utilization study that resulted in a new sludge stabilization facility at its 26-mgd wastewater treatment plant.The new 2nd generation Autothermal Thermophilic Aerobic Digestion (ATAD) facility boasts a processing capacity of 34,000 dry pounds per day and is the largest in North America. Since coming online in May 2009, the facility has reduced solids volume, eliminated odor and regulatory complaints, and continues to practice beneficial reuse via land application.