[Changes of Microbial Community Structure in Activated Sludge Bulking at Low Temperature].

The mechanism of activated sludge bulking in Zhengzhou wastewater treatment plant was studied by measurement of water quality parameters and high-throughput sequencing technology. The change of SVI value was significantly negatively correlated with the seasonal temperature variation, and sludge bulking was easy to occur during December to the next April, but the water quality was not affected. The result verified by high-throughput sequencing technology analysis showed that the microbial community structure of bulking sludge was significantly different from that of the non-bulking one. The dominant filamentous bacteria in the bulking sludge in this plant were Saprospiraceae and Flavobacterium. Therefore, the activated sludge bulking in this wastewater treatment plant was caused by the propagation of filamentous bacteria at low temperature.

[Biodegradability of extracellular polymeric substances (EPS) produced by aerobic granules].

Aerobic granules were cultivated with synthetic wastewater and were added in the course of aerobic starvation. Results showed that EPS produced by aerobic granules was composed of 40% biodegradable and 60% nonbiodegradable EPS. Among these, only biodegradable EPS could be utilized by their producers, while nonbiodegradable EPS contributed to maintain the spatial structures of aerobic granules. EPS extracted from fresh aerobic granules was fed as the sole carbon source to their own producers and activated sludge and was utilized by them. The average biodegradation rate of activated sludge in terms of EPS was 1.5 times faster than that of aerobic granules. When EPS extracted from starved aerobic granules was fed as the sole carbon source to their own producers and activated sludge, it could not be utilized and could not be energy source.