Three phase flow behaviour of granular upflow anaerobic sludge blanket reactors.
Anaerobic upflow sludge blanket (UASB) bioreactors are widely applied for industrial wastewetar treatment. Their development started by the research team of Gatze Lettinga in 1970s and the technology was rapidly abosrbed by the industry. These bioreactors are special because they rely on either formation of heavy microbial flocs or dense microbial granules that have excellent settling properties with the latter settling much faster compared to flocs. The good settleability of microbial aggregates allows to keep a high concentration of them in the bioreactors and consequently high volumes of wastewater can be treated in a relatively small volume. Thus stable and strong granules are key to design compact bioreactors.
Despite the fact that the technology is widely applied, even experiened practitioners have faced a problem where granules at full scale become unstable and disintegrate without an obvious reason. This is because there is still no consensus on the mechanisms of granulation and ideal conditions for granulation are not fully undesrtood. One factor that is believed to affect granulation is the hydrodynamic behaviour of these reactors. In this project we are working on the development of a 3-phase computational fluid dynamics model to describe hydrodynamics of these reactors at lab-scale. Perhaps even more importantly we are working on experimental determination of flow fields of various phases in these reactors.
The role of organic substrate and shear forces on anaerobic sludge granulation