No bio foul-up at Sydney Olympics

US Filter Australia-Vivendi Water is supplying a wastewater reclamation plant that will recycle sewage and rainwater runoff at the Sydney Olympic Games Site in Homebush Bay.

US Filter Australia/Vivendi Water is supplying a wastewater reclamation plant that will recycle sewage and rainwater runoff at the Sydney Olympic Games Site in Homebush Bay.

Part of the purification process will involve the use of reverse osmosis technology from Dow. The recycled water will be used for irrigation and toilet flushing at the Olympic Games Village and Homebush Bay Olympic Games facilities.

The water treatment plant has been designed to produce 7.5 ML/day of filtered water and 2.0 ML/day of desalinated water. The plant has been designed to handle a mixture of treated and reclaimed sewage water and surface water runoff, and a dual membrane process is used to achieve the required purity of the treated water.

The dual membrane process uses Memcor CMF microfiltration technology and reverse osmosis, using fouling resistant Filmtec membranes from Dow. The US Filter CMF micro-filtration unit allows continuous filtration down to 0.2 microns, but reverse osmosis is required at the next level in order to purify the water to the molecular level.

Natural conditions working against the Olympic Games organisers include warm weather, nutrient rich water sources, and the presence of micro-organisms negatively effect the efficiency of standard RO purification units.

Bio-fouling blocks the flow of water through the membrane and effects the production of fresh water. A single, viable micro-organism replicating every twenty minutes under ideal conditions can produce a progeny and plugging legacy in excess of 4.7 x 1021 within twenty four hours.

The biological species of concern for RO system operators are those that adhere to the inside of the membrane surface and excrete a sticky mass which traps nutrients for the microscopic creatures that create them.

The Filmtec Fouling Resistant membrane is a surface modified polyamide that resists bacterial adhesion. This is said to extend the time between membrane cleaning and increases cleaning efficiency, whilst maintaining high salt rejection and the productivity performance of standard RO elements.

The Filmtec FR elements are constructed using automated element construction. The use of automation results in a higher level of precision, impossible to achieve using traditional manual manufacturing methods.

Because of this level of precision there are fewer gaps inside the membrane for organisms to set up housekeeping. In traditional, hand rolled membranes not only are there more spaces for organisms to grow, but a rougher surface area is also a better place for the organisms to stick and cultivate.