Glycogen accumulating population and its anaerobic substrate uptake in anaerobic-aerobic activated sludge without biological phosphorus removal

The presence of a glycogen accumulating population and its abilities of substrate uptake and storage in anaerobic-aerobic activated sludge fed with mainly acetate were investigated. Because a low phosphorus/carbon feeding ratio (2/100, wt/wt) was used to suppress the growth of polyphosphate-accumulating bacteria, the sludge exhibited no biological phosphorus removal activity. Still, under anaerobic conditions, acetate, propionate, butyrate, valerate, pyruvate, lactate, most key intermediates in the tricarboxylic acid cycle, and gluconate were taken up and stored as polyhydroxyalkanoate (PHA); and glucose, fructose, maltose, sucrose, trehalose, and raffinose as cellular glycogen and PHA. The energy and reducing equivalents required for the carbon uptake and storage were generated from the glycolysis of either cellular glycogen or a sugar taken up. Results of substrate uptake further suggested that the sludge preferred to utilize glucose instead of cellular glycogen as an energy source during acids uptake. Different morphological types of bacteria with deposits of cellular PHA granules after substrate uptake were observed as the majority in the sludge, suggesting that they could assimilate or possibly scavenge most of the dissolved substrate of the waste water and dominate in the deteriorated biological phosphorus removal processes.