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This work aims to reduce membrane fouling by reducing the amount of solute at the membrane surface. Fouling reduces throughput and productivity of membrane systems and as such increases operating costs and reduces profitability of water treatment industries. This is achieved by implementing destabilizing electro-osmotic flow control. The significance of this project lies in linking feedback control of electro-osmotic effects with spacer design to maximize flow instabilities. This project will advance modelling of flow in membrane channels and develop a novel feedback flow control strategy that enhances mixing. The effectiveness and operability of the new fouling reduction approach on real-world membrane systems will be evaluated.

Recent research outcomes include:

1. Characterizing and designing localized electro-osmotic effects in a membrane channel using CFD simulations. A slip velocity with a time-varying waveform was imposed at the membrane surface to mimic the electroosmotic flow effect in the membrane channel. Analysis of the hydrodynamic and mass transfer characteristics in the channel has shown that electroosmotic flow instability enhances mass transfer. Greater mass transfer was observed with increasing voltage. The optimal frequency of the input voltage was identified from the frequency response analysis.
2. Experimental studies on electro-osmotic flow effects. This includes the design and building of the electrodes, membrane channel, electrical field actuation devices and local velocity (CTA) sensor. Experimental studies were conducted with a high voltage amplifier to introduce the electroosmotic field with different frequencies in a small channel with salt water. An EMI minimisation strategy was developed for the CTA sensor. The effect of the electro-osmotic field on the flow in the membrane channel was detected, showing some indication of enhanced mixing.
3. The preliminary theoretical feedback control. An optimal control algorithm was developed based on the measurement of the gradient of the velocities near the wall of the membrane. The CFD simulations with the proposed control show the “ideal” waveform of the voltage applied to the electrodes.
4. The operability of membrane systems. While it was too early to study the impact of the electroosmotic fouling reduction technique on membrane system operation, generic issues of membrane processes, including mitigation of the variation in feed concentrations, effects of multi-stage filtration and recycle streams were studied.