Efforts are on worldwide to make desalination units more energy efficient and environment-friendly. Water has always been a volatile topic in Australia, the world's driest inhabited continent. Yet, protesters are complaining that a planned desalination facility outside Melbourne, Victoria, will generate too much freshwater. The $3-billion government-owned plant will produce more than 300,000 cubic meters of drinkable water a day when it opens in 2011, placing it among the world's biggest. Environmental groups claim that the plant is unnecessary. Even if water consumption rose by 25 percent, there would be an excess of about 60 percent in supply over consumption by 2016! "Desalination is the most energy-intensive form of water supply," says Peter Gleick, president of the Pacific Institute, an independent environmental think-tank in Oakland, California. In California alone, proposals have been put forward for at least 20 new large desalination facilities, which together could ultimately supply some 6 percent of the state's urban water demand. Even the very energy-intensive thermal plants in the Gulf region, which purify seawater by boiling and condensing, can produce fresh water at less than $1 per cubic meter. And the desalination plant at Ashkelon in Israel, once the world's largest, produces more than 300,000 cubic meters of freshwater per day at costs of around 50 cents per cubic meter. But on average, the technique is 3.5 times more expensive than using other sources of freshwater such as pumping from aquifers. Technological future Advances in chemical engineering promise to make desalination more affordable. Polyamide membranes are the basic components of reverse-osmosis plants, which produce more than half of the world's desalinated water and are replacing less-efficient thermal distillation facilities. To remove dissolved organic matter and other impurities, brackish water or seawater is pre-filtered and then forced under pressure through bundles of these semi-permeable membranes, which separate salts from the water. Pretreatment cannot fully prevent the membranes from fouling and degrading, so they need to be cleaned chemically and replaced frequently