ABSTRACT
Aerobic digestion is employed to stabilize sludge and to lower its solids content. Aerobic digestion is a valuable process for industrial waste application, when convenience and ease of operation overshadow any concern for recoverable energy. Aerobic digestion is best described as a continuation of the basic biological system involving first the destruction of remaining substrate organics and formation of cells, followed by the endogenous respiration of the cells. Theoretical aerobic digestion models are usually based on first-order kinetics, with the final form dependent on the process configuration. Pure oxygen aerobic digestion is an emerging technology in which pure oxygen replaces air as the oxidant, possibly applicable for large installations. Thermophilic aerobic digestion or autothermal aerobic digestion is an emerging technology developed to operate in the thermophilic zone, utilizing heat energy released from the reaction to sustain process conditions. Cryophilic digestion involves low-temperature operation, applicable to small treatment plants at cold climatic conditions.
