Bioremedation consists of utiilsing living organisms (such as bacteria, fungi and plants) to absorb organic-molecules, subsequently converting them into safer byproducts such as carbon dioxide and water. It is more common to utilise bacteria in an aquatic environment.
The process can be carried out on either land or water, but has gained some attention in recent years, especially following the 2010 Deepwater Horizon (Gulf of Mexico) Oil Spill. Studies conducted along Pensacola Beach, Florida, USA, revealed carbon concentrations (C8 to C40) varied between 3.1 to 4,500 mg/kg in beach sands. Overall, approximately 4.93 million barrels (± 10%) of crude oil was released into the environment.
Generally speaking, bioremediation can be carried out either at the site of the pollution (in situ) or the polluted substrate can be transferred to site with a bioreactor for treatment (ex situ). The overall process is briefly discussed and illustrated in this video.
In conjunction with bioremediation, surfactants also play an important role in oil clean-ups, whereby they lower the oil’s surface tension. These disperse the oil throughout the water (into droplets) successively allows bacteria to begin degrading the oil. Whilst this might play an important role in disspating oil, careful considerations must be made to ensure that the surfactant will not subsequently contribute to pollution.
Traditionally, petroleum-based solvents were used. However, these are generally more toxic and rapidly disperse within aquatic environments. Modern surfactants, on the other hand, utilise non-aromatic, carbon-based, water-mixable solvents. Common surfactants include ethoxylated fatty alcohol. ethoxylated sorbitan fatty acid esters and tall oil esters. Nowithstanding this, various factors influence a dispersant’s effectiveness. These include an oil’s properties, wave-mixing energy, water temperature and salinity.
One of the major fallbacks with bioremediation is that the presence of metals and/or inorganic compounds at abnormally high levels in an environment, such as lead and sodium chloride respectively. These may hinder the process or simply render it unviable.
Overall, there are some promising signs in the field of bioremediation, with further R&D contributing to safer and more effective surfacants, being produced and applied in more financially-viable ways. Regardless, preventing oil spills is should always remain as the priority.
The United States Environmental Protection Agency (US EPA) has ongoing monitoring of the oil clean-ups following the 2010 Oil Spill. Progress of the clean-up efforts can be observed here.