Shear stress in a pressure-driven membrane system and its impact on membrane fouling from a hydrodynamic condition perspective: a review

Pressure-driven membrane technology has gained increasing popularity in municipal/domestic and industrial wastewater treatment, desalination, and water reclamation. Careful manipulation of surface shear stress, which plays a vital role in membrane fouling control from a purely hydrodynamic perspective, can minimise concentration polarisation of solute on flat sheet membranes, or enhance the particle back transport from hollow fibre membranes. This review considers the techniques to generate turbulence and shear at the membrane surface, the magnitude of shear stress, and the experimental, as well as numerical methods for evaluation of shear stress. The findings are presented in terms of the amount of shear stress reported to control membrane fouling in these systems. Operational disadvantages of fouling control via application of shear stress occur while changing the properties of the solute or particles, such as cell breakup, bacterial population change, or shear stress classification. The literature teaches that future developments on shear stress for membrane systems must be addressed, in addition to energy consumption, shear stress distribution and the development of combined analytical methods to characterise and visualise shear in situ for different membrane configurations.