Unconventional approach produces ultra-pure water

April 1 2008, A new Scandinavian spin-off company is researching a novel way to remove the worst contaminants from water using carbon dioxide gas. Traditional water-purification techniques such as filtration or distillation attempt to remove the contaminants from water by fluid flow. This new technology reverses conventional thinking by drawing clean water molecules away from the contaminated matter leaving ultra pure water.

The company behind the new technique - ECOWAT AS - is a spin-off from the SINTEF Group, a research organization based in Norway, headed by former SINTEF scientist Tore Skjetne.

“The less contamination that remains in the water, the more will traditional purification methods struggle to make the water completely pure. But we don’t have this problem; the less contamination left in the water, the more efficient is our technique,” explains Skjetne.

The ECOWAT process begins by transforming water molecules into crystals known as gas hydrates. Gas hydrates are compounds that form when molecules of gas meet water molecules under particular conditions of temperature and pressure. The gas hydrates are formed when carbon dioxide gas is brought into contaminated water at high pressure and low temperature. The water and the CO2 molecules grow together into tiny spherical snowflakes – without the water droplets becoming enclosed in the crystals. This makes the hydrates resemble dry snow, which is important as the product does not block the pores in the purification plant.

The snow-like material is then separated from the contaminated fluid by centrifugation and when it thaws the majority of the CO2 evaporates. This CO2 can also be used in the purification process.

To date, very large units of equipment are needed to remove compounds such household detergents or oil from water. If water has to be ultra-purified, which is required by pharmaceutical and food industries the only way to obtain it has been to use energy-intensive distillation. The ECOWAT will have a much smaller and more energy efficient system.

The first planned use for ECOWAT is to produce pure water to be used in gas turbines on offshore installations which will help to reduce greenhouse gas emissions. Ultra pure water can be introduced in the gas turbines as steam which can lower the combustion temperature and reduce the emissions of environmentally damaging gases.

“Our aim is to be able to supply water for use in offshore turbines in 2010,” says Tore Skjetne. “This sector alone is a billion Norwegian kroner market.”