Angular vibrations for fouling control during ultrafiltration of microalgae in a spiral wound module

Abstract

Previous studies have shown that vibration- or rotation-based techniques can effectively mitigate the fouling and concentration polarization during membrane filtration. However, it is difficult to incorporate these active enhancement techniques with spiral wound modules (SWMs), which are widely employed in drinking water and wastewater treatment. In this work a prototype membrane system was developed to accommodate angular vibrations with a modified SWM. With this prototype system, a series of filtration experiments were designed and implemented to investigate the effect of angular vibrations on the ultrafiltration algal fouling process in an SWM. The experimental results indicate that the algal fouling in an SWM can be effectively controlled (up to ∼28.5 % at 15 Hz) by applying angular vibrations in conjunction with appropriate operating conditions; the underlying mechanisms are discussed using a mathematical model that accounts for the relative motion between the fluid and membrane when they are subject to external accelerations, related to the vibration frequency, filtration period and position along coiled membrane leaves. A quantitative analysis is also presented to demonstrate the potential of using angular oscillations to control the algal fouling in an SWM with a lower energy consumption compared to the conventional method of increasing the cross-flow rate.