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首页> 外文期刊>Journal of Membrane Science >Biofouling of reverse osmosis membranes: Role of biofilm-enhanced osmotic pressure
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Biofouling of reverse osmosis membranes: Role of biofilm-enhanced osmotic pressure

机译：反渗透膜的生物污染：生物膜增强渗透压的作用

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A bench-scale investigation of RO biofouling with Pseudomonas aeruginosa PA01 was conducted in order to elucidate the mechanisms governing the decline in RO membrane performance caused by cell deposition and biofilm growth. A sharp decline in permeate water flux and a concomitant increase in salt passage were observed following the inoculation of the RO test unit with a late exponential culture of P. aeruginosa PA01 under enhanced biofouling conditions. The decrease in permeate flux and salt rejection is attributed to the growth of a biofilm comprised of bacterial cells and their self-produced extracellular polymeric substances (EPS). Biofilm growth dynamics on the RO membrane surface are observed using confocal microscopy, where active cells, dead cells, and EPS are monitored. We propose that the biofilm deteriorates membrane performance by increasing both the trans-membrane osmotic pressure and hydraulic resistance. By comparing the decrease in permeate flux and salt rejection upon fouling with dead cells of P. aeruginosa PA01 and upon biofilm growth on the membrane surface, we can distinguish between these two fouling mechanisms. Bacterial cells on the membrane hinder the back diffusion of salt, which results in elevated osmotic pressure on the membrane surface, and therefore a decrease in permeate flux and salt rejection. On the other hand, EPS contributes to the decline in membrane water flux by increasing the hydraulic resistance to permeate flow. Scanning electron microscope (SEM) images of dead cells and biofilm further support these proposed mechanisms. Biofilm imaging reveals an opaque EPS matrix surrounding P. aeruginosa PA01 cells that could provide hydraulic resistance to permeate flux. In contrast, SEM images taken after fouling runs with dead cells reveal a porous cake layer comprised of EPS-free individual cells that is likely to provide negligible resistance to permeate flow compared to the RO membrane resistance. We conclude that "biofilm-enhanced osmotic pressure" plays a dominant role in RO biofouling.
机译：为了阐明铜绿假单胞菌PA01对RO生物污染的实验规模，旨在阐明控制由细胞沉积和生物膜生长引起的RO膜性能下降的机制。在增强生物污染条件下，用铜绿假单胞菌PA01的后期指数培养物接种RO试验装置后，观察到渗透水通量急剧下降，并且盐通过量随之增加。渗透通量和脱盐率的降低归因于由细菌细胞及其自身产生的细胞外聚合物（EPS）组成的生物膜的生长。使用共聚焦显微镜观察反渗透膜表面生物膜的生长动力学，其中可以监测活性细胞，死细胞和EPS。我们建议生物膜通过增加跨膜渗透压和水力阻力来恶化膜性能。通过比较铜绿假单胞菌PA01死细胞结垢时和膜表面生物膜生长时渗透通量和盐截留率的降低，我们可以区分这两种结垢机理。膜上的细菌细胞阻碍了盐的向后扩散，从而导致膜表面的渗透压升高，从而降低了渗透通量和盐分截留率。另一方面，EPS通过增加渗透液的水力阻力而导致膜水通量的下降。死细胞和生物膜的扫描电子显微镜（SEM）图像进一步支持了这些提出的机制。生物膜成像显示，围绕铜绿假单胞菌PA01细胞的不透明EPS基质可为渗透通量提供水力阻力。相反，在用死细胞进行结垢后拍摄的SEM图像显示，由无EPS的单个细胞组成的多孔滤饼层与RO膜的阻力相比，可能对渗透流的阻力可忽略不计。我们得出结论，“生物膜增强的渗透压”在反渗透生物污垢中起着主导作用。

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