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Bioremediation

Bioremediation is a process in which certain eubacteria are used to degrade hazardous substances found in the environment. Recently bioremediation has been used to treat oil spills. Research on this process has been conducted on several oil spills, including the Exxon Valdez disaster in PrinceWilliam Sound, Alaska. How are eubacteria used in treating oil spills? Biodegradation is a natural process in which certain eubacteria is break down or consume petroleum and release carbon dioxide. These eubacteria are sometimes called hydrocarbon-oxidizing eubacteria because they destroy petroleum molecules by adding oxygen to them. The newly oxygenated molecules then are further broken down by the eubacteria until only end products remain.
Hydrocarbon-degrading eubacteria occur naturally although their numbers vary from one environment to another. In Prince William Sound and nearby areas the community of such degraders contains hundreds of different organisms that act together to degrade the petroleum and its product.
Eubacteria that degrade hydrocarbon require three components to grow: hydrocarbons, oxygen and nutrients. Oxygen is plentiful on the surface layers of the beaches in Prince William Sound because of their contact with the air. Normally the population of hydrocarbon-degrading eubacteria is the Exxon Valdez spill, these eubacteria accounted for less than 0.1 percent of the naturally occurring eubacteria found on the beaches. After the oil spill the availability of hydrocarbons was unlimited and the hydrocarbon-degrading eubacteria accounted for more than 10 percent of all eubacteria on the beaches. Any further growth in the population of these eubacteria is limited only by the availability of nutrients such as nitrogen and phosphorus.
One way to increase the population of these naturally occurring eubacteria is to add the nutrients as fertilizers. The application of fertilizers to beaches is difficult however because tidal and wave action quickly wash away water soluble nutrients. In addition introducing nitrogen and phosphorus into sheltered bays and estuaries might cause algal blooms and eutrophication. To minimize these problems researchers have developed several special methods for applying fertilizers. One method uses fertilizers that stick to or dissolve in the oil, another use granules that release the fertilizer over several days or weeks and a third uses an automatic spray system apply fertilizer at low tide.

In May 1989 the Environmental Protection Agency and Exxon agreed to test the different fertilizer application strategies on an island in Prince William Sound. After application of the fertilizer developed to stick to the oil, the beaches showed a perceptible improvement within 10 days. The beaches were monitored during and after the test applications to determine any adverse affects. To date none have been recorded. Apparently the number of eubacteria returns to normal levels after the fertilizer has been used or washed away. Researchers continue to be concerned however about the effects of introducing high levels of fertilizers into marine ecosystems.
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