Biodegradation is the process by which an organic

Biodegradation is the
process by which an organic substance is broken down into smaller
compounds by microorganisms (Marinescu et al., 2009). It is the biologically catalyzed degradation in convolution of chemical compounds
(Alexander, 1994). According to the interim army policy on natural attenuation for environmental restoration (1995), natural attenuation, or bioattenuation, is
the reduction of pollutant concentrations in the environment through biological procedures, physical occurrences, or chemical reactions. One of the most significant components
of this process is biodegradation. Microorganisms can help
with the chemical reactions that alter the form of contaminants and lessen the
risk to all living things. However, the correct conditions must exist
underground to clean the polluted sites thoroughly. These conditions are observed to make sure that natural attenuation is happening. This process is called monitored
natural attenuation (MNA). MNA is a method used to oversee or examine
the development of bioattenuation processes that can reduce contaminants
in soil and groundwater. It can be done with other bioremediation processes as a final option or it can be the only remediation process if the rate of contaminant degradation is fast enough to
protect human health and the environment. Natural processes can then
moderate the residual amount of pollution, regular
monitoring of the soil and groundwater can confirm those degradations
(EPA, 2001). If the natural
attenuation is not quick enough or not finished, bioremediation will be improved by either biostimulation or
bioaugmentation. Biostimulation involves the adding of soil nutrients, trace minerals, electron
acceptors, or electron donors. It enhances the biotransformation of a wide range of soil contaminants (Li CH et al.,
2010). Bioaugmentation can be defined as the technique for improvement of the capacity of a
contaminated matrix (soil or other biotope) to remove pollution by the
introduction of specific competent strains or consortia of microorganisms (Thierry et al., 2008). Bioaugmentation method can be utilized when
biostimulation and natural attenuation have failed
(El Fantroussi et al., 2005).