Whether it is a television, a car, a telephone pole, a baby stroller, or a living room carpet, the products of industry inevitably have been produced at the expenses of resources used and wastes generated. The wastes are widely varied, ranging from carbon dioxide, to heavy metals, such as lead or mercury, and a host of complex organic molecules never before found in nature.
Earlier in this century we were not aware of the hazards that these wastes can pose, and there was little or no control of their use and disposal. Gradually, new regulations were instituted for the disposal of hazardous waste materials, but they did not take into consideration some of the problematic environmental legacies that have since been discovered.
We now know that in some cases hazardous wastes previously disposed of using the common engineering practice of the times have leached into the groundwater, posing a degree of health hazard still being debated. With the goal of reducing environmental contamination, the U.S. Environmental Protection Agency (EPA) and state environmental regulators have been upgrading standards for using and disposing of hazardous wastes. In response, some industries are now pursuing their own research into ways of reducing environmental contamination, and a new confluence of cooperating specialists is emerging. Multidisciplinary teams of scientists from academic, regulatory, and industrial organizations are learning how to establish at the site of contamination microecosystems that can clean up the soil and water that have been contaminated by hazardous industrial wastes.
Instead of the expensive process of gathering up the polluted material and transporting it to another location for permanent burial and isolation, or chemical or thermal destruction, it is increasingly possible to treat the hazardous wastes where they are by using living organisms that can metabolize the wastes. This is called in-situ bioremediation, which for the purposes of this article will include "on-site" bioremediation, in which the polluted material remains on the site but is moved within the site.
Although research now underway points to manufacturing process that recycle, eliminate, or properly contain many of today's hazardous industrial wastes, the challenge for the present is to restore the soils and water already contaminated by industrial wastes and to minimize ongoing environmental contamination by industrial wastes. In-situ bioremediation is a response to these needs. This process requires that the hazardous wastes be served up as food for appropriate organisms. If the wastes contain toxic heavy metals, such as mercury, the heavy metals must be removed before the remainder of the wastes can be biodegraded. [See "Bioremediation," p.303.]
Even with the heavy metals removed, degradation of hazardous wastes is not an automatic process. Just as human life requires an adequate diet, a suitable temperature, and air to breathe, microorganisms require a source of nutrients, the proper temperature, and the right amount of oxygen. Aerobes require an oxygen source, while anaerobes require protection from oxygen. This is relatively easy to do in a bioreactor, which is designed for optimal degradation of the pollutant. However, establishing all of these conditions in-situ is seldom easy.
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