Bridging the gap between membrane bio-reactor (MBR) pilot and plant studies

An integrated numerical approach was developed and implemented to study the hydrodynamic characteristics of pilot and plant systems of membrane bio-reactor (MBR). The approach incorporated Eulerian multiphase model, porous medium scheme, and also successfully took into account the vertically dependent filtration flux and the effect of mixed liquor suspended solids (MLSS) on mixed liquor viscosity. Utilizing this integrated numerical approach, a clear distinction of up-flow and down-flow regions within the pilot single module had been simulated. The simulated mixed liquor velocity and air hold-up agreed well with published experimental measurements and theoretical estimation, respectively. However, when a total of 160 modules were consolidated into an actual plant operation (i.e. Plant A), the average mixed liquor and air velocities of each module encountered a drop of approximately 50-80% lower compared to the pilot system. This implied that an approach applicable for the studies on both pilot and plant simulations was essential to identify and subsequently improve the problem. One example of optimization was by enlarging the tank size for the plant system (i.e. Plant 13). With this minor design modification, the mixed liquor and air velocities were improved by 50% and noticeable up-flow and down-flow circulations were achieved. (C) 2008 Published by Elsevier B.V.