G6.1: Anaerobic Digester - Steady States, Transients and Control

Abstract The model of Andrews and Graef (1974) was used as a basis of simulation of stationary and dynamic behaviour of an anaerobic digester. It was found, that multiple stable stationary states exist in the continuously operated digester. The feed-batch type of operation can give higher substrate conversion than the continuous operation. The introduction of the time-lag into the microorganism growth function causes appearance of both stable and unstable periodic states of the digester. The questions of controllability and the possibilities of multivariable control strategy has been discussed.