Notice of RetractionEffect of filamentous bacteria on the operation of membrane bioreactor (MBR)

Notice of Retraction

After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE´s Publication Principles.

We hereby retract the content of this paper. Reasonable effort should be made to remove all past references to this paper.

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The effects of the conditions of nitrogen- and phosphorus-deficiency on the filamentous abundance index (FI), the removal efficiency of pollutants and the membrane fouling were investigated. The results indicated that the removal efficiency of COD_Cr reduced obviously at nitrogen deficiency and FI was higher than that at phosphorus deficiency. When filamentous bulking happened, FI increased and the micro-animals: swimming ciliates→vorticella→rotifers→Epistylis→arcella became the dominant population in turn, which could be indicative for the operation of the MBR. When FI increased from 2 to 4, Zeta potential lowered and extracellular polymeric substances (EPS) and the relative hydrophobicity (RH) in the mixed liquor rose sharply, that accelerated the membrane fouling. Filamentous bulking has the important influence on the RH of membrane, the dynamic contact angles of polluted membrane were 64°(FI=1), 67°(FI=2), 71°(FI=3), 76°(FI=4)and 81°(FI=5), respectively. The increase of EPS and sludge volume index (SVI) has reinforced the adsorption of filamentous bacteria on the membrane surface, which caused the membrane fouling to become more serious. Filamentous bulking, which influenced the operation of MBR, should be avoided in MBR.