is a waste management technique that involves the use of organisms to remove or neutralize pollutants from a contaminated site. According to the United States EPA, bioremediation is a “treatment that uses naturally occurring organisms to break down hazardous
substances into less toxic
or non toxic substances”. Technologies can be generally classified as in situ
or ex situ
. In situ
bioremediation involves treating the contaminated material at the site, while ex situ
involves the removal
of the contaminated material to be treated elsewhere. Some examples of bioremediation related technologies are phytoremediation, bioventing, bioleaching, landfarming, bioreactor, composting, bioaugmentation, rhizofiltration, and biostimulation.
Bioremediation may occur on its own (natural attenuation or intrinsic bioremediation) or may only effectively occur through the addition of fertilizers, oxygen, etc.,that help in enhancing the growth of the pollution-eating microbes within the medium (biostimulation). For example, the US Army Corps of Engineers demonstrated that windrowing and aeration of petroleum-contaminated soils enhanced
bioremediation using the technique of landfarming. Depleted soil nitrogen status may encourage biodegradation
of some nitrogenous organic chemicals, and soil materials with a high capacity to adsorb pollutants may slow down biodegradation owing
to limited bioavailability of the chemicals to microbes. Recent advancements have also proven successful via the addition of matched microbe strains to the medium to enhance the resident
microbe population's ability to break down contaminants. Microorganisms used to perform the function of bioremediation are known as bioremediators
However, not all contaminants are easily treated by bioremediation using microorganisms. For example, heavy metals
such as cadmium
and lead are not readily absorbed or captured by microorganisms. A recent experiment
, however, suggests that fish bones have some success absorbing lead from contaminated soil. Bone char has been shown to bioremediate small amounts of cadmium, copper, and zinc. A recent experiment, suggests that the removals of pollutants (nitrate, silicate, chromium
and sulphide) from tannery wastewater were studied in batch
experiments using marine microalgae. The assimilation of metals such as mercury
into the food chain
may worsen matters. Phytoremediation is useful in these circumstances because natural plants or transgenic plants are able to bioaccumulate these toxins in their above-ground parts, which are then harvested for removal. The heavy metals in the harvested biomass may be further concentrated by incineration or even recycled for industrial use. Some damaged artifacts at museums contain microbes which could be specified as bio remediating agents. In contrast to this situation, other contaminants, such as aromatic hydrocarbons as are common in petroleum, are relatively simple targets for microbial degradation, and some soils may even have some capacity to autoremediate, as it were, owing to the presence of autochthonous microbial communities capable of degrading these compounds.
The elimination of a wide range of pollutants and wastes from the environment requires increasing our understanding of the relative importance of different pathways and regulatory networks to carbon
flux in particular environments and for particular compounds, and they will certainly accelerate the development of bioremediation technologies and biotransformation processes.