Biostimulation involves the modification of the environment to stimulate existing
bacteria capable of
bioremediation. This can be done by addition of various forms of rate limiting
nutrients and
electron acceptors, such as
phosphorus,
nitrogen,
oxygen, or
carbon (e.g. in the form of
molasses). Additives are usually added to the subsurface through injection wells, although injection well technology for biostimulation purposes is still emerging. Removal of the contaminated material is also an option, albeit an expensive one. Biostimulation can be enhanced by
bioaugmentation. This process, overall, is referred to as
bioremediation and is an
EPA-approved method for reversing the presence of oil or gas spills.