Aerobic granules were obtained from a laboratory-scale sequential aerobic sludge blanket (SASB) bioreactor fed with glucose as the main source of
carbon and energy. Aerobic granules at different growth stages which are conventionally called as young, mature, old, and disrupted granules (Fig. 7.2), were selected manually using following principles:
(1) young granules are those of regular shape, smooth surface, and their diameters are smaller than 2 mm;
(2) mature granules are those with diameters bigger than 2 mm, fluffy edge, and without black core inside;
(3) old granules are those with diameters bigger than 1 mm and with black core inside;
(4) disrupted granules have irregular shape and appear as fluffy flocs.
The observation of the different growth stages of aerobic granules implied that the development of aerobic granules might go through a sequence of specific, but poorly understood chemical and biological processes. The investigation on tracking the microbial population dynamics from young to old granules would provide important information to identify the key organisms in aerobic granules development. This information would in turn provide useful physiological indicators for the purpose of monitoring and controlling this novel wastewater treatment process.
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