Effect of Organic Loading and DO on Stability of Hypersaline Aerobic Granular Sludge
Published on: 2015-08-15
In order to investigate the effect of organic loading and dissolved oxygen (DO) on the characteristics of hypersaline aerobic granular sludge in some sequencing batch reactors (SBR), the indicators of sludge were analyzed such as the sludge volume index (SVI), minimal sedimentation rate, dehydrogenase activity, extracellular polymeric substances (EPS) component and size distribution of granule. Results indicate that the effect of organic loading and DO on the stability of aerobic granular sludge is significant. The organic loading which is over low or over high does not go against the stability of granular sludge. Over high organic loading can inhibit the growth of granular sludge and decrease the dehydrogenase activity and the content of extracellular proteins (PN), which cause granular sludge disintegrate and worse stability of granular sludge. The content of EPS in granular sludge achieves maximum under the organic loading of 5.4 kgCOD•(m3•d)-1, and the EPS is given priority to with extracellular proteins, resulting in the larger of average particle size, uniform of size distribution, thus the granular sludge displays a good stability. Over low DO can easily trigger filamentous bacteria breeding, and which can cause that granular sludge is unstable, increasing DO concentration can promote the growth of granular sludge, and the size distribution can be more concentrated, but over high DO can affect the stability of the system, because providing over high hydraulic shear force can lead to granular sludge disintegrating. When the reactor is controlled under DO of 6mg•L-1, the EPS is mainly with extracellular polysaccharide.