Contamination soil is a state where man-made chemicals enter and change the natural soil environment. Contamination occurs because of leakage of liquid wastes or industrial chemicals or commercial facilities; the use of pesticides; entry of contaminated surface water into the sub-surface layer; accident vehicle transporting oil, chemicals, or waste, waste water from a landfill and industrial waste is disposed into the soil are not eligible (illegal dumping).
Various hazardous chemicals contamination cases from oil extraction activities. The processes of exploration, exploitation and production of oil bear risks of oil spill contamination. These risks can be found in various stages of the process. Therefore, management, and reprocessing of oil-contaminated soil will be required. The treatment will be aimed to halt the spread and absorption of the oil into the layers of the ground.
Treatment of oil-contaminated soil areas can be done through biological means by applying the capabilities of certain microorganisms. These microorganisms can degrade the hydrocarbon structure of the contaminant material into becoming simpler minerals which are harmless for the environment. Such technique is also known as bioremediation.
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Bioremediation is the development of environmental biotechnology using biological processes to control pollution. Bioremediation is not a new concept in applied microbiology, because the microbes have been widely used for many years in reducing organic compounds and toxic materials are both derived from household waste as well as from industry. Bioremediation techniques proved very effective and inexpensive to control the pollution of soil and water are contaminated by toxic chemical compounds.
Bioremediation techniques can be carried out either in-situ or ex-site. An in-situ bioremediation techniques are normally applied to lightly-contaminated locations, unmovable areas, or in circumstances where the contaminant material(s) is volatile. An ex-situ bioremediation implies the action of moving the contaminated areas/water body into a specific area where it would be procesed for bioremediation. This process shall involve microorganisms to lower the concentrations of poison within the contaminant. By using natural, bio-degradable microorganisms, this method can be considered as environment-safe.
Compared with other remediation techniques, application of bioremediation is much cheaper. Levine and Gealt (1993) states that for a yard in bioremediation of contaminated soils is required to spend about 40 to 100 dollars. While through other processes, such as by incineration, requires a fee of 250 to 800 dollars and landfilling of about 150 to 250 dollars for the same capacity of the soil. Bioremediation can be applied in environments polluted through various mechanisms. Litchfield (1991), bioremediation is done through the following five approaches: bioreactors, solid-phase treatment, composting, landfarming, and treatment of in situ.