Sunday, 30 January 2011

How are oil spills cleaned up?

How are oil spills cleaned up?
Mystic, Connecticut
Dear Alina:
When an oil tanker runs aground or wrecks in the ocean (as recently happened off northwestern Spain), one of the first questions many people ask is "How will that mess get cleaned up?" While the specifics of the cleaning process vary according to the type and location of the spill, groups such as the Office of Response and Restoration (part of the National Oceanic and Atmospheric Administration) and the International Tanker Owners Pollution Federation Ltd. share the same general plans of attack.The key methods for cleaning up oil spills are:
  • Booms -- Floating barriers placed around the oil or around whatever is leaking the oil. Booms contain the oil so skimmers can collect it.
  • Skimmers -- Boats, vacuum machines, and oil-absorbent plastic ropes that skim spilled oil from the water's surface after booms have corralled it. The skimmer collects oil into a container so it can be removed.
  • Chemical dispersants -- Materials that break down the oil into its chemical constituents. This helps disperse the oil and make it less harmful to wildlife and shorelines.
  • In-situ burning -- Igniting freshly spilled oil while it's still floating on the water.
Booms, skimmers, and chemical dispersants are perhaps the most frequently used methods to clean up ocean oil spills. Every method has its advantages and disadvantages, and the effectiveness of any cleaning method depends on ocean currents and tides, as well as the weather. Some methods can be as harmful to the environment as the oil spill itself. National governments also regulate what chemicals can be used in the ocean.If the spilled oil reaches shore, experts use another set of cleaning methods. Low- or high-pressure water hoses can wash oil off beaches, as can vacuum trucks. Sponge-like materials called "sorbents" can absorb oil and are often used in the final stages of cleanup. Even shovels and road equipment can come in handy to remove oily sand and gravel from a beach. Sometimes the sand and gravel are cleaned elsewhere and replaced on the beach. Animals, such as sea birds, must be washed by human hands using a diluted solution of dishwashing liquid. Unfortunately, even careful cleaning will not save all oiled birds.
Oil spills in rivers pose slightly different problems, but similar methods are used as to clean them up. In rivers, there are often plants much closer to the water, and it's very difficult to remove oil from plants. Oiled vegetation can be flushed with water to remove the oil, but severely damaged plants will need to be destroyed and removed entirely.