Modeling the performance of an anaerobic baffled reactor with the variation of hydraulic retention time

• A novel model is developed to simulate ABR performance with a variation of HRT.
• Biomass retention factor is introduced into the IWA ADM1.
• Liquid–gas transfer is integrated into the biochemistry process derived from ADM1.
• The model provides a holistic insight into the anaerobic process in ABRs.

Anaerobic baffled reactors (ABRs) have been widely used in engineering but very few models have been developed to simulate its performance. Based on the integration of biomass retention and liquid–gas mass transfer of biogas into the biochemical process derived in the International Water Association (IWA) Anaerobic Digestion Model No.1 (ADM1), a mathematical model was developed to predict volatile fatty acids (VFAs), chemical oxygen demand (CODCr) and biogas in a 4-compartment ABR operated with variable hydraulic retention time (HRT). The model was calibrated and validated with the experimental data obtained from the reactor when the HRT decreased from 2.0 to 1.0 d by stages. It was found that the predicted VFAs, CODCr and biogas agreed well with the experimental data. Consequently, the developed model was a reliable tool to enhance the understanding among the mechanisms of the anaerobic digestion in ABRs, as well as to reactor’s designing and operation.