Membrane Bioreactors: Appropriate Technology for Water Purification in South Africa?

Membrane Bioreactors represent the concrescence of the two highly exciting and rapidly evolving fields of biotechnology and materials science. By definition, a membrane bioreactor is any system that integrated membrane separation and biological transformation. The applications range from tissue engineering for bio-artificial organ development, through the production of high-value products, to water purification and wastewater re-use. The first application of a membrane bioreactor for waste treatment was reported when Smith et al. (1969) used an ultrafiltration (UF) membrane to re-circulate activated sludge back to the aeration tank. Subsequently, 4 major membrane bioreactor formats have evolved, which are currently researched or applied. These 4 formats are 1) biomass retention bioreactors, 2) Bubbleless oxygenation bioreactors, 3) Fixed film reactors and 4) extractive membrane bioreactors. These will be dealt with individually below. Formats and applications Biomass Retention Bioreactors Reactors of this type, in which a microfiltration (MF) or UF membrane at as a separation barrier to retain and recycle high molecular weight compounds and biomass to a conventional tank reactor, are by the far the most established membrane bioreactor technology in use for waste treatment. This reactor type i