Low pressure membrane processes - doing more with less energy

This paper discusses strategies to reduce energy usage in low pressure membrane processes. Studies on the role of air bubbling to control fouling in submerged membrane systems are described. Factors of importance are shown to include fibre movement and the use of the most appropriate bubble size. Results are given that favour the use of small bubbles, and this is supported by shear stress analysis using particle image velocimetry. It is also shown, for deadend filtration of low solids feed, that the optimal flux based on conventional economics is much greater than the optimal flux based on minimization of energy usage. This observation may be of general applicability and illustrates the capital cost penalty inherent in minimizing environmental impact of membrane processes.