New inexpensive method to clean oil from water

The rainbow effect caused by varying thicknesses of oil film on water’s surface might be pretty to look at but is indicative of polluted water. This “oil sheen” proves especially difficult to remove, even when the water is aerated with ozone or filtered through sand. But now a University of Utah engineer 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.

The new process created by Andy Hong, a professor of civil and environmental engineering at the University of Utah, uses two existing technologies – ozone aeration and sand filtration – but significantly changes the former method. Instead of attempting to turn the entire hydrocarbon (oil) content in the water into carbon dioxide and water by just bubbling ozone through polluted water, the new process converts it into a form that can be retained by sand filtration.

To achieve this Hong 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.

Compared with larger bubbles from normal ozone aeration, the tiny bubbles provide much more surface area for the oxygen in ozone to react chemically with the oil. Hong says pollutants tend to accumulate on the bubbles because they are not very water-soluble and 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 a sheen – into acids and chemicals known as aldehydes and ketones. Most of those substances, in turn, help the remaining oil droplets to clump together so they can be removed by conventional sand filtration, he adds.

Hong says his method could be used to clean a variety of pollutants in water, including refinery wastewater and oil spills at refineries or on waterways where the spill could be vacuumed, and then treated on-site or on a barge. Hong also says so-called “produced water” from oil and gas drilling sites on land, which normally is re-injected underground, could instead be treated and put to beneficial uses, such as irrigation, especially in arid regions where oil and gas tend to be produced.

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Tags: andy hong, dirty water, hydrocarbon oil, inexpensive method to clean oil from water, microscopic bubbles, oil content, oil film, polluted water, rainbow effect, tiny bubbles

This entry was posted on Wednesday, November 18th, 2009 at 9:22 am and is filed under Cutting-edge Research, Innovation, environment, gizmag. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.