**2. Limitations of bioremediation**

in situ bioremediation include are biosparging, bioventing, in situ biodegradation, and bioaugmentation. The *Deinococcus radiodurans* is used for metal remediation in radioactively

Crude oil is a mixture of thousands of varying chemical compounds. Given that composition of each type of oil is unique, there are different ways to bioremediate them using microbes and flora. Bioremediation can occur naturally or can be encourage with addition of microbes and

The microbes present in the soil at early stage recognize the oil and its constituents by biosurfactants and bio emulsifiers. After this, they attach themselves and use the hydrocarbon present in the petroleum as a source of energy. However, low solubility and adsorption of high molecular weight hydrocarbons can pose as a limiting factor to their availability to microor‐ ganisms. But, addition of biosurfactants enhances the solubility and removal of these contam‐

Volatility, volubility, and susceptibility to biodegradation differ distinctly among constituents of crude oil. Some compounds are easily degraded, some resist degradation and some are nonbiodegradable (Mukred *et al*.,2008). Yet, biodegradation of different petroleum compounds occurs simultaneously but at different rates because different species of microbes preferentially attack different compounds. This scenario leads to progressive and successive disappearance

Microbes produce enzymes in the presence of carbon sources, and these enzymes are respon‐ sible for the break down of hydrocarbon molecules. Many different enzymes and metabolic pathways are involved in the degradation of hydrocarbons contained in crude oil polluted soils. It implies that complete hydrocarbon degradation requires an appropriate enzyme,

Bioremediation has various benefits of outstanding environmental and agricultural

People perceive bioremediation as an acceptable strategy for the transformation of a wide

Byproducts from bioremediation treatment are usually harmless products. Such residues include carbon dioxide, water, and cellular biomass, implying that most hazardous contami‐ nants can be transformed to harmless products thereby eliminating the chance of future

Processes involved in bioremediation can be conducted on-site without causing a major disruption of normal activities of the ecosystem. But, this, they need to transport quantities of waste off site and the potential threats to human health and the environment that can arise

Bioremediation is cheap when compared with other technologies that are used for clean-up of toxic waste. Some of the contaminants are sources of energy to the soil microbes thereby sustaining microbial biodiversity. Certain bacteria are mobile and exhibit a chemotactic

unavailability of which either prevents or minimizes its breakdown.

variety of pollutants, often involving recycling (Polprasert, 1989).

response, sensing the contaminant and moving toward it.

liability associated with treatment and disposal of contaminated material.

inants. Again, rates of oil biodegradations increases with addition of biosurfactants.

polluted environments (Brim *et al*.,2000).

348 Environmental Risk Assessment of Soil Contamination

of constituents of crude oil over time.

during transportation are eliminated.

fertilizers.

implications.

