Bioparticle characteristics of tapered anaerobic fluidized-bed bioreactors

When the volumetric loading is greater than 50 kg-COD/m3-d, the performance of the tapered anaerobic fluidized-bed bioreactors is more efficient than that of the conventional anaerobic fluidized-bed bioreactor; however, the increasing percentages of the COD removal efficiency are not very significant when the taper angle is greater than 5°. The arithmetic means of the biofilm thickness, specific surface area and specific biomass of the former (increased with the increasing taper angle) are all larger than those of the latter; and the distribution of bioparticles in the former is more uniform than that in the latter. There is a fairly good agreement between the experimental and simulated removal efficiencies of the substrate, and thus, the proposed kinetic model can be used for the predicting purpose. The sensitivity analysis result together with the calculated values of Thiele modulus and the effectiveness factor reveal that the acetate methanogenesis in the anaerobic fluidized-bed bioreactors is reaction-controlled, and the biofilm is fully penetrated by the substrate.