Bioremediation is a managed or spontaneous process in which microbiological processes are used to degrade or transform contaminants to less toxic or nontoxic forms, thereby mitigating or eliminating environmental contamination. In the presence of sufficient oxygen (aerobic conditions) and nutrients, microorganisms will ultimately convert many organic contaminants to carbon dioxide, water and microbial cell mass. In the absence of oxygen (anaerobic conditions), the electron acceptor is a compund other than molecular oxygen, such as sulfate, nitrate, or carbon dioxide, and the contaminants will be ultimately metabolized to methane, limited amounts of carbon dioxide, and a trace amount of hydrogen gas.
Advantages to the technology include its ability to ideally transform toxic compounds to harmless substances without disturbing the subsurface. The limitations and criteria for application of in situ bioremediation, such as the degree of cleanup achievable, and potential to produce toxic byproducts must be understood prior to its implementation.