Inhibition of biofouling in membrane bioreactor by metabolic uncoupler based on controlling microorganisms accumulation and quorum sensing signals secretion.

Biofouling is a limiting bottleneck in the development of membrane bioreactor (MBR) since the birth of this technology. Recently, the biofouling control strategy based on interfering with the bacterial quorum sensing (QS) system is highly desirable for biofouling control in MBR. In this study, three lab-scale parallel MBR systems were operated over 100 days to investigate the inhibitory effect of a metabolic uncoupler (3,3',4',5-tetrachlorosalicylanilide, TCS) on biofouling and the potential mechanism for biofouling control. Compared to the control MBR, the fouling cycle duration of MBR 2 with 100 μg/L TCS extended over two times. The attached biomass on membrane in MBR 2 decreased over 50% at the end of each operating period, which indicated that the addition of TCS significantly mitigated microorganisms accumulation on membrane. The content of interspecies QS signal (autoinducer-2) and intraspecific QS signals (N-octanoyl--homoserine lactone, C8-HSL) was reduced by the TCS, suggesting the secretion of QS signals in MBR were affected by uncoupler. Although the addition of TCS induced brief fluctuations of extracellular proteins and polysaccharides, microorganisms seemed to rapidly acclimatize to the presence of TCS and then the secretion of extracellular polymeric substances (EPS) was inhibited by 100 μg/L TCS. The continuous operation of MBR was not be affected by the low-concentration uncoupler via the analysis of substrate removal and sludge growth. This study systematically evaluated the effect and inhibitory efficiency of TCS on biofouling, biomass accumulation, QS signals, EPS and treatment performances, demonstrating the feasibility of metabolic uncoupler for biofouling control in MBR.