- Analysis by Cristen Conger
Oil skimmers enlisted to sop up an estimated 71.2 to 139 million gallons of oil spewed from the Deepwater Horizon site generally consist of equipment to corral the greasy pools and skimming mechanisms to suck up the oil-seawater solution. According to the Associated Press, the ragtag armada has removed around 33 million gallons of oil across hundreds of square miles of oil-drenched water.
Due to the size of the Deepwater Horizon spill, oil skimming has been an all-hands-on-deck effort, comprised of commercial oil skimming vessels maintained by BP, other companies, private boats retrofitted with skimming equipment and oil skimmers maintained by the U.S. Coast Guard.
“The Coast Guard has 24 Vessels of Opportunity skimming systems strategically located throughout the country…and most have been moved down to the Gulf region in response to the spill,” said Michael Popovich, environmental equipment specialist for First Coast Guard District, District Response Advisory Team.
Following the Exxon Valdez spill in Prince William Sound, the Oil Pollution Act of 1990 required the Coast Guard and oil companies to maintain emergency oil skimmers, like the Coast Guard’s Vessels of Opportunity, in case of a similar environmental catastrophe.
Yet, over the past 20 years, not much has changed about how oil skimmers work.
“(Oil skimming) is a mechanical means of removal, so there’s not a lot of high tech to it,” Popovich said. “It’s just a time-consuming process of trying to pick that oil up off the surface, and some skimming platforms are better than others.”
Since oil spreads over the surface of seawater, the skimming process usually begins by lassoing giant puddles of oil with floating barriers called containment booms. Then, skimmer mechanisms attempt to siphon oil from the water for disposal or reuse.
But smoothly separating fluids with two different viscosities isn’t easy.
“Even in the most ideal (weather) conditions, you’re still going to get a percentage of water and a percentage of oil when you skim,” Popovich told Discovery News.
To further complicate water and oil’s sticky relationship, the type of oil leaked and the amount of time it floats around impacts viscosity and, in turn, skimming success. Consequently, Popovich says the oil skimmers cleaning up the Deepwater Horizon spill employ a “multitude” of methods.
For instance, the Coast Guard Vessels of Opportunity use weir skimmer systems that collect oil using floating separators that disrupt the water-oil interface where the two liquids meet.
On the other hand, liquid separation skimmers promoted by actor Kevin Costner and recently commissioned by BP spin oil-water emulsions in centrifuges that essentially skim and separate at the same time.
In shallower waters near shorelines, belt skimmers attract oil with bands of oleophilic (oil-loving) material that are then squeezed dry.
“You have big plastic drums that rotate, and the oil adheres to it and you scrape it off,” said Tim Lindsey, associate director of the Illinois Sustainable Technology Center. “That’s pretty primitive technology.”
Lindsey has developed a prototype for a new floating telescoping weir skimming system he claims could dramatically improve oil skimming efficiency.
“The problem with most of the current (oil skimmers) they’re using is they have to come in direct contact with the oil to work,” Lindsey said. “You have to go back and forth across the water as though you’re mowing the lawn or vacuuming the floor, and when you’re in an environmentally sensitive area, that’s a problem because of the damage you can do by trying to make contact."
His proposed solution diverts oil with the floating weirs and then runs it through an oil-coalescing material, such as polypropylene balls, that fully extracts the oil.
And Tim Lindsey isn’t the only one tossing oil skimming suggestions BP’s way. When he submitted his prototype to the company two weeks ago, Lindsey said his was one of 65,000 proposals already being considered.
Louisiana State University engineer Chandra Theegala also has ideas about how to de-oil the Gulf with less time and money.
“Our (patent-pending) LSU skimmer overcomes several of the existing limitations,” Theegala said.“It’s simple and has no moving parts other than a commercially available and well-proven pump, so there’s nothing to break. As it doesn’t require a centrifuge, the energy requirements are small."
In light of the Deepwater Horizon disaster, the recent flood of oil skimming innovation after two decades of relative standstill makes sense, as Theegala explains.
“The Exxon Valdez sparked new interest in skimming and related technologies in the ‘90s; however, when the interest and mechanisms for funding dry up, researchers no longer pursue it actively." Theegala explained. “Then, when we have a major oil spill like the current BP spill, we are totally unprepared. I ‘m hoping the same story will not get repeated now.”
Although progress may seem slow, Coast Guard specialist Popovich urges the public to recognize the inherent difficulty of scooping oil slicks off the mercurial seawater surface, and BP’s oil skimmer downsizing may signal that the vessels are making a dent in cleaning up the massive spill.
“The oil that’s out there is going to continue to weather, and the skimming platforms out there … will become more efficient in recovering oil, so it’s tough to say how long it’ll take to recover,” Popovich said. “Certainly several more weeks is probably on the low end, and that’s based on whether any more oil is introduced into the environment.”
http://news.discovery.com/tech
AP Photo/Pat Sullivan
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