UV assisted backwashing for fouling control in membrane bioreactor operation

Membrane fouling is a major bottleneck to cost effective application of membrane bioreactor (MBR) for wastewater treatment. This study evaluated a novel fouling control strategy of using UV irradiation to enhance the effectiveness of backwashing. Coupling UV irradiation with NaClO backwashing resulted in significantly lower membrane fouling, suggesting a higher fouling control efficacy than only NaClO backwashing. The signal molecule (C8-HSL) monitoring results suggested the NaClO backwashing could remove the foulants but lead to bacterial stress and thus resulted in more signal molecule being secreted by the microorganisms in the MBR. In contrast, UV irradiation in the mixed liquor constantly suppressed the signal molecule levels and thereby inhibited the fouling development. The confocal laser scanning microscopy analysis suggested that the significant formation of large bacterial aggregates on the membrane surface were avoided after UV assisted backwashing compared to permeate or NaClO backwashing without UV irradiation. Besides, the UV assisted backwashing did not significantly affect the microbial community structure and compromise the water treatment performance of the MBR.