Mitigating membrane fouling with sinusoidal spacers

Membrane fouling is a major drawback of reverse osmosis (RO) membrane filtration as it negatively affects the quantity and quality of the treated water and the lifespan of the membrane. Spacers play a pivotal role in the hydrodynamics of the membrane channel thus influencing membrane fouling. Building on our previous work (Xie et al., Journal of Membrane Science, 2014, 453:92-99) where a series of novel sinusoidal spacers were built, we investigate here the spacers' ability to mitigate foulant deposition onto membrane surfaces. Experiments were performed and a three-dimensional computational fluid dynamics (CFD) model was built. The results of experiments with humic acid and calcium ions (a surrogate foulant recipe) showed that certain sinusoidal spacers had less fouling than mesh spacers. Furthermore, the fouling on membranes diminished as the tortuosity (ratio of amplitude to wavelength of the sinusoidal pattern) increased. CFD simulations explored the development of fouling over time and the CFD results were compared with scanned images of fouled membranes. The simulation results matched well with the experimental results and suggested that wall shear stress alteration by the spacers could be a mechanism for fouling reduction.