Microbial community in biofilm on membrane surface of submerged MBR: effect of in-line cleaning chemical agent

The objective of this study was to investigate the change in microbial community pattern with the effect of cleaning agent using a quinone profile that is used for membrane in-line chemical cleaning in SMBR. The dominant quinone types of biofilm were ubiquinone (UQs)-8, -10, followed by menaquinone (MKs)-8(H-4), -7 and UQ-9, but those of suspended microorganisms were UQ-8, UQ-10 followed by MKs-8(H-4), -7 and -11. Both UQ and MK contents decreased with increasing NaClO dosage and it seems that there is more resistance from UQ compared to MK. In addition, COD and DOC concentrations increased with increasing NaClO dosage up to 0.05 g-NaClO/g-SS. The organic degradation performance of the microbial community in the presence of NaClO was impaired. The present study suggested that larger added amounts of NaClO caused an inhibition of organic degradation and cell lysis.