Distribution characteristics of extracellular polymeric substances and cells of aerobic granules cultivated in a continuous‐flow airlift reactor

Abstract BACKGROUND: Most studies on the cultivation of aerobic granules to date have been based on the sequencing batch reactor ( SBR ). A continuous flow airlift fluidized bed reactor ( CAFB ) was set up, and the operating conditions which promoted granulation in the SBR were not controlled. The distribution characteristics of extracellular polymeric substances ( EPS ) and cells of the aerobic granules were studied under these operating conditions. RESULTS: Cells, polysaccharide and protein were all distributed uniformly throughout the granules, confirmed by both confocal laser scanning microscopy and scanning electron microscopy observations. However, for the granules in the SBR , the core of the granules was usually composed of protein and dead cells, and living cells survived only in their outer layers. Such a distribution of granules in the CAFB was confirmed to be related to the advanced oxygen transfer ability and strong shear force in the CAFB . Even microbial cells in the center were supplied with sufficient food to maintain bioactivity. Thus, the CAFB performed COD removal very efficiently. CONCLUSION: Cells and EPS in the aerobic granules of a CAFB were more uniformly distributed compared with those in granules of the reported SBR reactors, owing to the particular operating conditions of the CAFB . © 2012 Society of Chemical Industry