Analysis of integrated kinetic and flow models for anaerobic digesters

Abstract

Abstract The objective of this paper is to develop anaerobic digestion models that integrate features from the kinetics of the process with those from flow (or hydraulic) behavior in modern anaerobic digesters. First, a detailed kinetic model based on the one described in Kalyuzhnyi [S.V. Kalyuzhnyi, Batch anaerobic digestion of glucose and its mathematical modeling. II. Description, verification and application of model, Bioresour. Technol. 59 (1997) 249–258] was modified to account the production of endogenous residue. The two digesters studied in this work are the UASB (upflow anaerobic sludge blanket) and the EGSB (expanded granular sludge bed) reactors. The flow models for those digesters have to take into account the different flow behaviors for the effluent and the sludge. The flow model for the UASB reactor was based on that of Bolle et al. [W.L. Bolle, J. van Breugel, G.C. van Eybergen, N.W.F. Kossen, W. van Gils, Kinetics of anaerobic purification of industrial wastewater, Biotechnol. Bioeng. 28 (1986) 542–548], which was generalized in this work to take into account the volume variations of the reactor sections in non-steady state. The model for the EGSB reactor was developed from the experimental results described in Brito and Melo [A.G. Brito, L.F. Melo, A simplified analysis of reaction and mass transfer in UASB and EGSB reactors, Environ. Technol. 18 (1997) 35–44]. With the kinetic and flow models, integrated models for anaerobic digestion in selected modern anaerobic digesters are developed and validated, and many simulations of these models under different scenarios are described. In particular, the anaerobic digestion in an UASB reactor simulation shows that the volume variations of the sections of this reactor proposed in this work are necessary to accurately describe the behavior of such digester in non-steady state.