Reducing the membrane fouling in cross-flow filtration using a facile fluidic oscillator

Abstract

Membrane fouling is a main factor that hinders the wide spread adoption of membrane filtration process. In this study, we demonstrate that a passive fluidic oscillator can effectively reduce the fouling and enhance the permeate flux in cross-flow microfiltration. The oscillator produces a pulsating flow of frequency 56–115 Hz and pressure amplitude 500–700 kPa, which leads to transient high shear rates, surface scouring and back-flushing effects. As a result, it mitigates the concentration polarization, prevents micropores clogging, and inhibits the formation of fouling layer. Its applications for filtration of an inorganic particulate suspension and an organic macromolecular solution, as well as the effect of the operating pressure of the oscillator and the membrane material were investigated. In comparison with the static filtration, the membrane fouling was significantly reduced for both the feed solutions using the oscillator. The current method was further tested for recovery of bacterial capsular polysaccharide from 100 L of pneumococcus fermentation broth. The recovery ratio was improved from 2.0% to 39.3% using the conventional method to around 100% with the oscillator. The process time was also greatly reduced by 30%. Furthermore, though the oscillator provides dynamic filtration, it works under constant pressure without the need of additional motors and stirrers. Potentially, it could be applied to some currently existing filtration systems, to improve the flux performance but without increasing too much the system complexity.