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Question: What is the process of bioremediation?
This is a particularly good question, especially in light of the increasing need to reclaim and reuse old industrial sites, and the need to deal with industrial accidents such as the recent Gulf of Mexico oil spill. Bioremediation is the use of living organisms to remove toxic or otherwise undesirable contaminants from the environment. At present bioremediation is best developed in the use of bacteria to remove hydrocarbon contaminants in the soil and ground water – e.g. from gasoline, oil, and solvent spills. In some cases the naturally occurring bacteria in the soil can be used, with the bacteria utilizing the hydrocarbon as "food", breaking it down to carbon dioxide and water. Fertilizers supplying the nitrogen and phosphorous (often limiting nutrients) may be applied to encourage the growth of the bacteria. In other cases the contaminated area is seeded with special strains of bacteria selected for their ability to break down the contaminants. It has also become apparent in recent years that interaction of the bacteria and soil fungi and green plants often improves the rate of contaminant removal. Applied bacteria and fertilizer have also been used, with varying success, to the clean-up of marine oil spills.
Bioremediation is also being explored as a way to remove toxic heavy metal contaminants, such as mercury, cadmium, zinc, and lead, from soil. Such contaminants may be naturally occurring, or be the result of industrial operations such as mining and smelting. Bacteria are not effective in this instance. Instead plants that "hyperaccumulate" the undesirable metal are being studied ('phytoremediation"). The plants are sown on the contaminated ground. As they grow they take up the metal ions from the soil, reducing the metal concentration in the soil while accumulating it in their tissues. The plants are then harvested, and disposed of in a suitable manner. Alternatively, the metal may be recovered from the harvested plant material.
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