Hydrodynamic characteristics of UASB granular sludge produced from combined anaerobic/aerobic treatment systems

The hydrodynamic characteristics of granular sludge is the key factor for efficient operation of up flow anaerobic sludge blanket (UASB) reactor, This research aims to evaluate the hydrodynamic characteristics of anaerobic sludge produced from five different pilot scale configurations, based on its settle ability, expansion characteristics and particle size distribution. An experimental set-up was established to determine the parameters required for settle ability and expandability equations. For particle size distribution, the proposed technique involves the determination of the settling velocities of a sludge sample then calculating the corresponding diameters using a mathematical approach. Results show that the hydrodynamic characteristics of different types of granular sludge have been determined using simple, flexible and low cost techniques. Results also indicated that sludge settling characteristics were not affected by adding supporting plastic media to the UASB reactor. On the contrary, the excess activated sludge returned to UASB reactor enhanced the sludge settling properties. The particle size distribution ranged from 0.06 to 1.1 mm and the corresponding Reynolds number (R e ) for most sludge granules are from 0.1 to 50 which demonstrates that the settling process of the granules is in intermediate flow regime.