Natural bioremediation of pollution is constantly occurring in the environment; without it, past pollution would still be present. Environmental biotechnology typically involves three types of organisms or biological systems: plants, microorganisms, and enzymes that may come from either group. Using plants to bioremediate an environment is referred to as phytoremediation. Phytoremediation is typically used when the environment is contami nated by heavy metals such as lead, mercury, or selenium. Certain plants (Astragalus, for example) are able to accumulate high concentrations of metals such as selenium in their tissues. The plants can be harvested, the tissue burned, and the metal-contaminated ash (now small in volume) can be stored in a hazardous waste facility.
Bioremediation most commonly refers to the use of soil microorganisms (bacteria and fungi) to degrade or immobilize pollutants. It can be used to treat a wide variety of wastes, including some nuclear wastes such as uranium. In one bioremediation process, the contaminated site is made favorable for microbial growth. Nutrients, such as nitrogen and phosphorus, are added. The area is kept moist and periodically stirred (if it is soil) to make sure it has sufficient air, or air is pumped into the system (if it is an aquifer). Microbes already present at the site start growing and use the waste as a food source.
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