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COMPARATIVE EVALUATION OF MESOPHILIC AND THERMOPHILIC DIGESTION - PHASE I. TEMPERATURE TRANSITION STUDIES
Citation:
Kugelman, I. AND V. Guida. COMPARATIVE EVALUATION OF MESOPHILIC AND THERMOPHILIC DIGESTION - PHASE I. TEMPERATURE TRANSITION STUDIES. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-89/001a.
Description:
As part of a larger study on the comparison between mesophilic and thermophilic anaerobic digestion, a study of the operation of anaerobic systems under temperature transition was conducted. Systems seeded with domestic sewage sludge, but subsequently fed a chemically defined complex medium, were operated at 20- and 30-day detention times at 35 C. The temperature was raised to 55 C at rates varying from 0.25 C to 2.5 C per day in duplicate, parallel units. Irrespective of temperature rise rate, as soon as the temperature exceeded 45 C methane production shut down. The units were held at 45 C until recovery occurred. Once recovery of methane production ability occurred, transition to 55 C took place with little incident except for minor difficulty at 51 C. Data analysis indicated that rate of temperature rise had little effect on the total time required to obtain stable operation at 55 C; detention time had a minor effect with longer detention time yielding superior result. Two other studies were conducted: a temperature drop study and a steady-state comparison between mesophilic and thermophilic operation. Sudden temperature drops below 50 C gave adverse effects. Steady-state mesophilic operation was superior, especially at lower detention times.