Ozone bubble method to remove polluted oil sheen from water

November 16th, 2009 - 4:35 pm ICT by ANI  

Washington, Nov 16 (ANI): The oil sheen frequently seen on polluted water can now be removed thanks to a new ozone bubble method developed by an University of Utah engineer.

Andy Hong, a professor of civil and environmental engineering has developed an inexpensive new method to remove oil sheen by repeatedly pressurizing and depressurizing ozone gas, creating microscopic 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,” said Hong.

In laboratory experiments, he showed 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.

He said that the method could be used to clean a variety of pollutants in water and even soil.

Hong said that his method uses two existing technologies - ozone aeration and sand filtration - and adds a big change to the former.

Instead of just bubbling ozone through polluted water, he uses repeated cycles of pressurization of ozone and dirty water so the ozone saturates the water, followed by depressurization so the ozone expands into numerous microbubbles in the polluted water, similar to the way a carbonated beverage foams and overflows if opened quickly.

The tiny bubbles provide much more surface area - compared with larger bubbles from normal ozone aeration - for the oxygen in ozone to react chemically with oil.

Hong says pollutants tend to accumulate on the bubbles because they are not very water-soluble.

The ozone in the bubble attacks certain pollutants because it is a strong oxidant.

The reactions convert most of the dispersed oil droplets - which float on water to cause sheen - into acids and chemicals known as aldehydes and ketones.

He added that most of those substances, in turn, help the remaining oil droplets clump together so they can be removed by conventional sand filtration.

Hong showed that the new method not only removes oil sheen, but also leaves the treated water so that any remaining acids, aldehydes and ketones are more vulnerable to being biodegraded by pollution-eating microbes.

The study has been published in the journal Chemosphere. (ANI)

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