Washington, Nov 16 (IANS) Oily deposits that pollute the sea and kill marine life could be cleaned up with a new method developed by an engineer.

Small amounts of oil leave a fluorescent sheen on polluted water. Oil sheen is hard to remove, even when the water is aerated with ozone or filtered through sand.

Now an University of Utah (U-U) engineer has developed a low cost method to remove oil sheen by repeatedly pressurising and depressurising ozone gas, creating tiny bubbles that attack the oil so it can be removed by sand filters.

'We are not trying to treat the entire hydrocarbon (oil) content in the water to turn it into carbon dioxide and water but we are converting it into a form that can be retained by sand filtration, which is a conventional and economical process,' says Andy Hong, professor of civil and environmental engineering.

In lab experiments, Hong demonstrated that 'pressure-assisted ozonation and sand filtration' effectively removes oil droplets dispersed in water, indicating it could be used to prevent oil sheen from wastewater discharged into coastal waters.

Hong says the method - for which patents are pending - also could be used to clean a variety of pollutants in water and even soil, including 'produced water' from oil and gas drilling sites on land, according to a varsity release.

Such oily water normally is re-injected underground. 'If we have technology to clean it, it could be put into beneficial uses, such as irrigation, especially in arid regions where oil and gas tend to be produced,' says Hong.

These findings were reported online this week in Chemosphere.