Designed to deliver up to 100 billion litres (100 gigalitres) of water each year, South Australia’s desalination plant at Port Stanvac, 25km southwest of Adelaide, is part of the state’s Water for Good plan to secure water for the future.

The facility will draw seawater from 1.4km off the coast and convert it to desalinated drinking water using a process known as reverse osmosis. During the process the sea water is pressurised and pushed through a series of superfine membranes. The dissolved salts and impurities are filtered out and collected as a saline concentrate, leaving desalinated drinking water which is 99% free of impurities.

The facility has been designed and built by AdelaideAqua, who will then operate and maintain the plant for 20 years. At the heart of the plant are two reverse osmosis buildings, each capable of delivering 150 million litres of desalinated water a day. Watson Fitzgerald & Associates have been working on the site for 12 months as the HVAC contractors with Company Director Peter Spencer as the Project Manager.

“The mechanical design includes a range of smoke exhaust, supply air and general exhaust fans, along with rotary vents and transfer fans from Fantech,” he said. “And because the plant processes salt water, all fans and components must be made from stainless steel or powder coated to prevent rust.

“The design is relatively simple; however, the large footprint of the two reverse osmosis buildings has made installation more difficult. Five Ø1800mm stainless steel axial smoke spill fans and attenuators had to be individually lifted onto the roof of the first building. Each unit weighed about 1.5 tonnes and had to be lifted 30 metres by a 130 tonne crane to reach its final support frame.

Fantech Sales Engineer Jean Butterfield said the desalination plant was the largest project the South Australian office had worked with. “Many of the fans were non-standard sizes and had to be built specifically for this project,” she said.

Another unusual aspect of the project was ventilating the tunnel pumping station which is located 40m underground.

The station is responsible for pumping sea water into the plant and discharging the concentrated saline back into the sea. These fans will be installed at ground level and ducted through to the pumping station below to ensure the motors are kept cool and remain in operation.

Peter said, at an estimated cost of $1.8 billion, the desalination plant was one of the largest infrastructure projects in the state. “There are currently about 1400 people employed on site, including 25 of our people”.

He said the first building was due to be completed mid-year. It is anticipated that it will start producing drinking water by the end of July 2011. Work has started on the second building and it should be completed in December 2012.