The 3 types of Bioremediation
The first type of bioremediation is biostimulation; nutrients in a gas or liquid form are added to soil or water where there is a need to remove contaminants. The bacteria are already there they are just stimulated to encourage growth and activity. Essencially the he bacteria turn the harmful substances in to CO2.
The second type of bioremediation is bio augmentation, where microorganisms are added to the soil to help remove contaminants. It is more commonly used in contaminants in the original site, and is more successful. It is not very helpful in sites of contamination rather than the original site because it is difficult to control the site conditions.
The third type of bioremediation is when it happens naturally in the contaminated area, such as a petroleum site like an old gas station. There is no other knowledge of it happening naturally in any other type of contaminated site.