Modeling of the anaerobic digestion of sewage sludge: Evaluation of several reactor configurations

Sewage sludge is usually degraded by means of anaerobic digestion in order to produce biogas and stabilized sludge. Several reactor configurations have been implemented or studied intending to optimize the process; however, there is a lack of reliable mathematical models that can be used for this purpose. This paper deals with that issue by using a simplified model for the anaerobic treatment of sewage sludge. The performance of a conventional continuous digester was compared with a plug-flow reactor and the influence of the recycle ratio, a two-phase system and the reactor size effect and the influence of the temperature in a thermophilic-mesophilic operation were evaluated.