By Antonia von Gottberg, Darren Lawrence and Christoph Kullmann
Membrane bioreactors (MBR) with submerged membrane modules have set the standard for the next generation of biological wastewater treatment plants as they offer two main advantages; a significantly improved effluent quality and a substantially smaller footprint. Besides the huge application in industrial wastewater treatment there are many municipal applications where MBR technology is being implemented. An example is the Bega Valley Sewerage Program (BWSP) in Australia which includes state-of-the-art MBR plants.
Bega Valley is located on the southeastern coastline of New South Wales (NSW). It includes the towns of Cobargo, Wolumla, Kalaru and Candelo. The capacity of the valley’s wastewater treatment systems was being stretched by urban growth and by seasonal population increases during the holiday period. Some unsewered villages in the valley were at risk for environmental and public health issues caused by discharge from septic tanks.
In order to maintain Australia’s Environment Protection Authority compliance and to enhance environmental outcomes, the Bega Valley Shire Council developed the Bega Valley Sewerage Program, which includes the installation of new pressurized sewage collection systems coupled with membrane bioreactor (MBR) treatment plants in the towns of Cobargo, Wolumla, Kalaru and Candelo (BVSP, 2004–2006). The Cobargo MBR plant was commissioned in July 2006 and Wolumla and Candelo were commissioned in 2007. Kalaru will follow sometime in 2008.
The entire program is designed to keep capital and operating costs at a minimum and to produce a very high quality effluent for reuse. Reclaimed water from the MBR plants will be used in an irrigation scheme on public facilities, replacing potable water as the primary source. In future, reclaimed water may also be used for toilet flushing and to provide a vehicle wash down facility.
Example of MBR Technology
There are many different configurations of MBR technology. One example that optimizes both membrane and module design is the PURON™ submerged hollow fiber UF module from the authors’ company. The patented module is designed to avoid the clogging and sludging that is an issue with some MBR module designs offered today. The module features hollow fiber membranes with a pore size of approximately 0.05 micron. The lower ends of the membrane fibers are fixed in a header while the upper ends are individually sealed and are free to move laterally. All solids and particulates remain on the outside of the fibers while permeate is sucked out of the inside of the fibers by means of a vacuum.
