Investigation of shear stress behavior on membrane surfaces in reciprocating membrane bioreactors using fluid-structure interaction simulations

Abstract

Although reciprocating membrane bioreactors (rMBRs) have been developed as energy-efficient wastewater treatment technologies, fouling removal mechanisms are yet to be elucidated. This study conducted simulations of fluid-structure interaction and experiments using particle image velocimetry to investigate the behavior of shear stress on the membrane surface in rMBRs. Simulations were performed on the three-dimensional model, varying parameters such as average reciprocating velocity (ARV), moving distance (MD), and membrane slack ratio (MSR). The results found that fluid advection can hinder foulant adhesion to the membranes. Increasing the ARV from 4 to 12 cm/s under shear stress resulted in higher fluid resistance and inertial forces, leading to elevated shear stress. The effect of MD on shear stress was negligible within the range of 4 - 12 cm. An intermediate level of MSR from 0 to 3% promoted turbulence around the membrane, thereby increasing shear stress. The response surface suggested that it may be desirable to simultaneously increase the ARV and MSR to maximize shear stress. However, this increase can also lead to stability failure by increasing the principal stress in the membrane potting area. This study provides insights into fouling removal mechanisms to improve the efficiency of rMBRs.