Bioremediation was born in the era of the 1980s when the US Federal Government commissioned a study of the interactions between toxic substances and the environment. Some sites were so profoundly contaminated that the costs and the damage to the sites would have been resistant to any solution. The damage to the sites from conventional solutions, such as removing massive quantities of soil and material, would have been catastrophically destructive, requiring even more money to restore the site to usefulness or to natural soundness.
The study was commissioned as a result of a lack of knowledge and understanding that was hampering the planned superfund cleanup program. The superfund approach provided a way to capitalize and to support cleanup of sites that were so profoundly toxic that no normal source of capital and resources could be found, since the costs of even one superfund project can exceed hundreds of billions or even a trillion dollars.
As a result of intensive study under the Toxic Substances Hydrology Program which was conducted by scientists from the USGS, the discovery that biological entities in shallow ponds and aquifers thrived and transported toxic substances. This discovery led to the idea of using biological entities to break down, modify or transport toxic material.
One of the largest and costly processes was to remove toxic soil in massive quantities. The new bioremediation programs change that process to one in which the toxicity is dealt with at the site. This is called “treating contamination in place”. Another cost saving process involves using biological and natural processes to remove, or at least contain toxic substances without humans being involved. This is called “harnessing natural processes”. Finally, these on site and natural processes save costs by reducing or eliminating the physical damage that is done to the site, requiring less restoration and repair when the toxicity is cleaned up.
In the case of fossil fuel pollution and toxcity in water, the study found that living organisms were breaking down the components of the fuel and converting them to carbon dioxide, which was harmless. In one study, tuolene was found to be completely eliminated by the natural process.
The organisms involved in bioremediation include bacterium, fungi, green plants and the enzymes that result from their processes. Chlorinated hydrocarbons can be dealt with by bacteria. With the addition of nitrate fertilizers, bacteria can break down oil spills. A process called phytoextraction has been used to remove salts from agricultural land for centuries, so bioremediation in some forms has been aroung for a while. Phytoremediation or phytoextraction is used in situations where heavy metals, such as cadmium, lead and mercury are taken up by certain plants, then removed when the plants are harvested.
In genetic engineering for bioremediation, a use is in radiation toxcity, where tuolene and ionic mercury is removed from radioactive waste by the Deinococcus Radiodurans, a genetically engineered bacteria that is the most radioactivity resistant organism that has ever been created.
Mycoremediation deals with fungi which break down lignin and celluose, and which have been targeted very specifically with sucess in projects. One specific fungus is capable of cleaning up the residue of VX and Sarin gases. Fungi produce enzymes and acids that can have specific properties for deconstructing and converting specific toxic materials.
There are also bioremediation processes of composting, bioaugmentation, rhizofiltration, biostimulation and bioventing.
The future of bioremedation is a bright one, as genetically engineered or naturally occurring life forms will always find an opportunity to break down the toxic chemicals, substances and compounds that mankind is capable of making in such massive quantities. It may even be possible to engineer predators to break down man made biotoxins, viruses and diseases. Also, the field of nanotechnology shows promise in creating synthetic and robotic versions of the natural biological processes that will help with in situ bioremediation.
http://water.usgs.gov/wid/html/bioremed.html
