Bioremediation of Environmental Contaminants in Soil, Water, and Air
Read full article onlineFull Article
The use of microbes, indigenous or foreign, in the cleanup of contaminated sites is termed bioremediation. Bioremediation has shown great promise in the removal of a wide variety of contaminants, especially at sites where the contaminant is widespread or is present at lower concentrations. Many larger contaminated sites have remained untreated because of high costs associated with traditional cleanup methods. Bioremediation is an attractive alternative to traditional clean up methods, because it may be performed on site, is less invasive, of lower overall costs than conventional methods, and can have higher public acceptance than harsher treatments. Bioremediation techniques are relatively inexpensive because capital and operating costs are generally much lower than, e.g., techniques such as soil removal and replacement. A study performed by Alper states that bioremediation is six times lower in cost than incineration and three times cheaper than entombment. Lower cost is a result of the lower energy and time requirements during the application phase of nutrient enhancements and the low cost of the nutrients because of their large-scale use in agriculture.
Bioremediation techniques are also safe and consistent with the natural processes occurring in the contaminated areas. As described later in this article, naturally occurring or indigenous organisms have been used exclusively up to the time of this writing. Indigenous organisms are present at the contaminated site and are therefore not added. Use of foreign or nonindigenous organisms remains a challenge for future research and development. Bioremediation can be applied to many situations including soil remediation, groundwater remediation, oil spills, and others as described below. Multiple contaminants can be attacked such as petroleum hydrocarbons, industrial solvents, organic wastes, and removal of metals.
The use of bioremediation does have its problems because it is a relatively immature technology where fundamental data still needs to be gathered. Information such as changes in the microbial community as biodegradation takes place is still lacking, due mainly to the fact that many of the microbes used in bioremediation cannot be successfully cultivated in a laboratory setting. For this reason, it is difficult to ascertain just how much removal of a contaminant observed in a study is directly a result of biological processes as opposed to other abiotic processes. We also do not know how the ecosystem is affected following the use of bioremediation except in the special case of the Exxon Valdez oil spill that has been extensively studied from the point of view of ecological impact. Bioremediation is still considered to be a new technology and thus many opt for using the more traditional and expensive cleanup methods. The role of government regulators in generating a favorable environment for introducing novel and effective treatments needs to be reassessed. Finally, although bioengineered microbes offer great promise for the removal of contaminants, public and regulatory acceptance of their use remains lacking. This situation is similar to the controversy surrounding the use of genetically engineered foods. This review will briefly discuss the current use of bioremediation for the removal of different types of contaminants, as well as the difficulties and benefits associated with the use of bioremediation in the removal of each contaminant.