Modelling of the Periodic Anaerobic Baffled Reactor (PABR) based on the retaining factor concept

The fact that the active biomass is continuously removed from the continuou sly stirred anaerobic digesters, leading to long retention times, has been overcome in a number of high rate systems based on immobilisation of the ac tive biomass, such as the Upflow Anaerobic Sludge Blanket Reactor (UASBR) a nd the Anaerobic Baffled Reactor (ABR). A kinetic model of glucose consumpt ion, which was developed based on a batch kinetic experiment, was used for the development of a dynamic model for the prediction of the behaviour of t he recently developed flexible reactor called the Periodic Anaerobic Baffle d Reactor (PABR) [(1998) Wat. Sci. Technol. 38(8-9), 401-408]. The PABR may be operated as a UASBR, an ABR or at an intermediate mode. The key assumpt ion of the model is that the hydraulic behaviour of a PABR is equivalent wi th the behaviour of CSTRs in series as concerning the dissolved matter, whe reas the biomass is allowed to be retained in the PABR through a retention factor accounting for precipitation. The model adequately predicted the exp erimental behaviour of a glucose fed PABR. The model was subsequently used to examine the behaviour of the PABR as a function of operating conditions, both for constant and varying loading rates. It was shown that for differe nt cases, the reactor should best be operated as a UASBR or as an ABR. (C) 2000 Elsevier Science Ltd. All rights reserved.