Application of anaerobic digestion model No. 1 on thermophilic anaerobic digestion with microbial immobilization media for biogas production from sugarcane vinasse

Anaerobic Digestion Model no.1 (ADM1) for the “Mixed Reactor Compartment” of AQUASIM with modified kinetic parameters was proven to be effective in predicting the behavior of thermophilic anaerobic digestion of sugarcane vinasse in a continuous stirred tank reactor (CSTR) equipped with unwoven textile as the microbial immobilization media. The modified kinetic parameters implied higher microbial growth rate constants in the CSTR with microbial immobilization media than the CSTR without media. The 16 s rRNA assay confirmed the inferences on the physical interpretation of the kinetic parameters. Microbial immobilization media shifted the initially homogeneous microbial composition in the CSTR's bulk liquid into methanogenic dominance in the biofilm attached to the media and acidogenic dominance in the liquid bulk after 90 days of operation. The remarkable finding of this study was that the segregated microorganisms indicated a beneficial micro-environment for both acidogenic and methanogenic populations to have favorable conditions for each of them. ADM1 well predicted the effect of this segregation with modified kinetic parameters and confirmed by the 16 s rRNA assay on the reactor's liquid and biofilm samples.