Pertinence of sludge settleability and membrane fouling in membrane bioreactor
膜-生物反应器中活性沉降性能与膜污染相关性研究

The evolution of activated sludge settleability and its pertinence to membrane fouling in a submerged membrane bioreactor were studied. It was found that SVI(sludge volume index)gradually increased and the sludge settleability was reduced, which was resulted by sludge bulking caused by filamentous bacteria growth. The pertinence of sludge settleability and membrane fouling was identified. With the escalating of SVI, the average increasing rate of transmembrane pressure increased, the stable filtration period was shortened, and the two stages (slow increase stage and rapid increase stage) of the transmembrane pressure were more obvious. At the same time, the increasing rates of transmembrane pressure at the slow increase stage and rapid increase stage increased and decreased with increased SVI respectively. The observation by using the scanning electronic microscopy presented the loosen structure and large thickness of the cake layer formed on the membrane surface when the sludge with filamentous bacteria and high SVI value was filtered. Influence of the sludge setteability on the transmembrane pressure was related with the structure and thickness of the cake layer on the membrane.