The Water Corporation of Western Australia turned on the country's largest seawater reverse osmosis (SWRO) plant back in November 2006, starting the delivery of a planned 45 gigalitres of drinking water a year into the Perth public supply system. Built by the Multiplex-Degremont Joint venture in alliance with the Water Corporation, the plant at Kwinana is the largest in the southern and eastern hemispheres. Bryan Orchard looks at the technologies involved.