Evaluation of the dual digestion system 2: operation and performance of the pure oxygen aerobic reactor

Abstract

In a comprehensive study of the performance of a full-scale (45 m3) pure oxygen autothermal thermophilic aerobic reactor of a sewage sludge dual digestion system, it was found that: Biological heat generation rate was directly proportional to the biological oxygen consumption rate at 13,1 MJ/kgO; respiration quotient (mol CO2 generated per mol O2 consumed) was 0,66; vent gas was saturated with water vapour even at the high vent gas flow rates; COD and/or VS removal rates were poor parameters for quantifying the biological heat generation rate and controlling the reactor temperature. Increases in reactor temperature could be completely and virtually instantaneously controlled by means of the oxygen supply rate (OSR) for as long as the reactor was oxygen limited. The rapidity of response and close correlation between the oxygen transfer rate (OTR) and the biological heat generation rate make the OTR and the OSR pivotal parameters in the operation, control, design and simulation of oxygen limited autothermal thermophilic aerobic reactors in dual digestion.