Abstract Fouling is the main hurdle for all membrane-based systems treating water with high fouling propensity. A novel imaging approach was applied in a forward osmosis (FO) system with spacers to follow in-situ and real-time deposition of fluorescent beads as bacteria proxy on the membrane using large-field high-resolution epifluorescence microscopy. For the first time, this study quantifies the impact of crossflow velocity (1.3 or 13 cm s-1) and permeate water flux (6 or 30 L m-2 h-1) on spatiotemporal patterns of initial cake layer formation (4 h). The total amount of deposited particles on the membrane increased by 84 fold as the ratio of permeate water flux over crossflow velocity, D, was raised by 54 fold. Spatial distribution of particles was more homogenous at higher D ratio, while particle accumulation rates decreased by 50% over 4 h. Distribution of local velocities of particle flow paths elucidated the observed spatial deposition patterns. These new quantitative results highlight that the ratio of permeate water flux over crossflow velocity impacts all aspects of particle deposition and may aid in designing new spacer geometries. We also suggest that appropriate hydrodynamic conditions may be a viable tool to postpone the onset of fouling in new and cleaned membrane modules.

中文翻译：

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地点、时间和原因？在正渗透中量化颗粒沉积与错流速度和渗透水通量的关系

摘要 污染是所有基于膜的系统处理具有高污染倾向的水的主要障碍。一种新的成像方法应用于带有垫片的正向渗透 (FO) 系统，以使用大视野高分辨率落射荧光显微镜跟踪荧光珠作为细菌代理在膜上的原位和实时沉积。本研究首次量化了错流速度（1.3 或 13 cm s-1）和渗透水通量（6 或 30 L m-2 h-1）对初始滤饼层形成（4 小时）时空模式的影响. 随着渗透水通量与错流速度 D 的比率增加 54 倍，膜上沉积颗粒的总量增加了 84 倍。在较高的 D 比下，颗粒的空间分布更均匀，而颗粒积累率在 4 小时内下降了 50%。粒子流动路径的局部速度分布阐明了观察到的空间沉积模式。这些新的定量结果强调，渗透水通量与横流速度的比率影响颗粒沉积的所有方面，并可能有助于设计新的间隔几何形状。我们还建议，适当的水动力条件可能是推迟新的和清洁过的膜组件中结垢发生的可行工具。