The causes of non-filamentous activated-sludge bulking in a long-term pilot-scale sequencing batch reactor(SBR)

Activated-sludge bulking was found in a pilot-scale SBR with long-term operation over 200 days,fed with real domestic wastewater. This paper focuses on the analysis of the relationship between sludge bulking and factors such as temperature,the content of extracellular polymeric substances (EPS),sludge loading and DO. The results showed that non-filamentous activated-sludge bulking generally occurred at low temperature (16℃),which led to poor settleability of the sludge. The MLSS of the SBR gradually decreased to less than 1200 mg·L-1 when non-filamentous activated-sludge bulking was found in the system. The content of EPS in the bulking sludge was higher than that in the normal sludge,and bulking sludge was difficult to recover although DO and temperature were 2.0 mg·L-1 and 20℃,respectively. Finally,the reasons causing activated-sludge bulking were analyzed and preventive approaches are suggested.