Bioremediation, or the use of hydrocarbon degrading microbes to clean up oil pollution, is a technique that has been receiving increasing attention in recent years.
Bioremediation has been categorized into two types: in situ and ex situ.
In situ bioremediation is the application of biological treatment used to clean up the hazardous chemicals in the soil or surface or subsurface waters. This is a low cost method involving the use of renewable resources like microbes and inflicts minimal site damage, and can be applied consistently. This method, however, is time consuming, and vulnerable to environmental factors that are beyond human control.
Efficient in situ bioremediation is achieved through a number oftechniques that include: seeding the saturated zone with exogenous inoculum, biosparging, bioventing, biostimulation & bioaugmentation and phytoremediation.
Ex situ bioremediation techniques require excavation of contaminated soil, or pumping of groundwater to facilitate microbial degradation and include methods such as landfarming, composting and formation of biopiles.
The gulf oil spill: In the aftermath of the Gulf crisis, enormous oil spill was encountered in the Bay of Gulf. Natural bioremediation of the oil spill at sea was achieved by naturally occurring oil degrading microorganisms. Artificial bioremediation of the oil spills was achieved by treating affected areas with cultures of oil degrading bacteria isolated from the populations that had developed naturally on the surface of the oil spills at sea and from the rhizospheres of desert plants, including Rhodococcus, Cellulomonas, Bacillus and Arthrobactor.
Ethical issue: Bioremediation may offer a useful addition to the range of options available in oil spill response. However the use of bioremediation remains a controversial issue as there appear to be conflicting reports regarding its effectiveness and very little is known about bioremediation in tropical marine environments. Its use in pristine marine environments is a matter of particular concern as it may involve the addition of nutrients (phosphates and nitrates) to the environment.