Demonstration of Thermophilic Aerobic-Anaerobic Digestion at Hagerstown, Maryland

摘要

This report describes the successful operation of a new and novel approach to digestion of sludge at the Hagerstown wastewater treatment plant. The process, known as dual digestion, involved the coupling of a full-scale experimental aerobic reactor to an existing full-scale anaerobic digester for the treatment of Hagerstown's raw sludge. In the process, sludge is aerobically digested at thermophilic conditions, using pure oxygen for about one day, followed by a longer period of 8 to 16 days of mesophilic (or thermophilic) anaerobic digestion. The system handled 16,400 gallons of raw sludge per day with average autothermal temperature in the aerobic digester of 51C. Pathogen analyses of the raw and digested sludge samples indicated the process significantly reduced pathogen levels beyond that achieved by conventional anaerobic digestion practice. The dual digestion process proved itself to be an effective sludge stabilization process achieving an overall volatile solids destruction of 42 percent.