Settling Properties of Activated Sludge from a Sequencing Batch Reactor (SBR)

The purpose of this work was to examine the settling properties of activated sludge from a sequencing batch reactor (SBR). The experiments were carried out in a bench-scale reactor, fed with wastewater from the University of Olsztyn treatment plant. Concentrations of the examined activated sludge varied between 2.5 and 6.0 kg SS m-3. Laboratory analyses of the sludge comprised: sludge concentration, settleability, sedimentation velocity and sludge volume index (SVI). The study revealed very good settling properties of the sludge. Low SVI (30- 60 ml g-1 SS) was responsible for an intensive and quick sedimentation which shortened the settle phase to less than one hour. Moreover, low SVI prevented the sludge from bulking. High dissolved oxygen concentrations in the aeration tank during the react phase resulted in little sludge biomass growth, which is very important from the viewpoint of sludge disposal at a wastewater treatment plant.