PRINCIPLES OF BIOREMEDIATION

Historial Perspective

In the past decade the United States has spent billions of dollars trying to clean up contaminated ground water and soils, the legacy of an era in which industry grew faster than knowledge about safe chemical disposal. Despite the large financial investment, ground water cleanup efforts are falling short of public expectations. Recent studies have revealed that, while conventional cleanup technologies have prevented the contamination problem from spreading, in most cases they are incapable of restoring the water to meet health-based standards in a reasonable time frame. Soil cleanups have been more successful in meeting regulatory standards. However, conventional soil cleanup methods may transfer contaminants to the air, posing risks that are not always acceptable to residents near the contaminated site. The limitations of conventional ground water cleanup technologies and the hazards of conventional soil cleanup methods have spurred investigations into in situ bioremediation, which uses microorganisms to destroy or immobilize contaminants in place.

Conventional methods for ground water cleanup rely on pumping water to the surface and treating it there. Such pump-and-treat methods are slow; they require the withdrawal of large volumes of water to flush contaminants from aquifer soilids, and they may leave behind reservoirs of contaminants that are lighter or denser than water and/or have low solubilities.

These systems consist of a series of wells used to pump water to the surface and a surface treatment facility used to clean the extracted water. This method can control contaminant migration, and, if recovery wells are located in the heart of the contaminant plume, it can remove contaminant mass. However, recent studies have shown that because many common contaminants become trapped in the subsurface, completely flushing them out may require the pumping of extremely large volumes of water over very long time periods. The surface treatment methods that are part of pump-and-treat systems use processes that transfer the contaminant to another medium (the air or the land) instead of destroying it.

Few people realize that In Situ bioremediation is not a new technology. The use of biooxidation for environmental purposes has been practiced for many years. In fact organisms have been on earth for some 3 billion years. The thick Grenville-Limestones suggest the presence of marine organisms of some sort existed in the Archeozoic Era. thus, the organisms have had a very long time to evolve, adapt and disperse. This long period likely also led to excellent survival strategies. Extended to micro biology that suggests that biodegrative traits found in one soil or groundwater would be found in most other soils or groundwaters around the world today.