Oil spillage takes place mostly from ships, posing hazards to the aquatic life to a large extent. Oceans get polluted with harmful chemicals due to seepage of oil (including petrol, diesel and other types of hydrocarbons) from ship wrecks, mishandling and accidents. The contaminated water when comes in contact with the soil, further pollutes it. The process of removing the toxic compounds from oceans and soil is quite tedious and expensive at the same time. Bioremediation is one such effective method of cleaning oils from soil and water, thereby making them safe for aquatic and terrestrial species.
What is Bioremediation?
Bioremediation is a scientific technique employed for removing pollutants from the soil and water surfaces with the help of microorganisms and their metabolic power. In situ bioremediation is usually carried out in places where the contamination is huge. A few species of bacteria, fungi and plants are capable of chelating heavy metals and different types of chemicals from soil and water. Such species are incorporated for the purpose of cleansing water bodies and lands. Today, scientists are designing microbes through genetic engineering process that can function in the same way.
The activity of the microbes are monitored in various ways. Scientists check the oxidation and redox potential of water and soil to find out if the process is taking place successfully. The chemical load, pH and the concentration of breakdown products are also taken into consideration for further determining the effectiveness of the microbes employed to carry out bioremediation. A chemical assay is also done with the help of indicators to check the density of electrons and to measure the microbial activity. We shall explain to you the different methods of bioremediation for oil contamination.
Bioremediation Methods for Oil Spills
Different techniques are applied either in situ or ex situ for eliminating toxic substances from the soil. The application of techniques depends on the nature and the intensity of the pollution. The microbes breakdown the chemicals with the help of the enzymes secreted by them. Thus, the soil or water becomes clear when the chemicals are taken up by them.
Using Bacterial Species
Pseudomonas is a potent bacteria that is capable of degrading hydrocarbons from petrol and diesel, thereby reducing the impact of oil spills. P. alcaligenes is capable of breaking down polycyclic aromatic hydrocarbons while P. mendocina and P. putida can remove toluene. P. veronii can degrade large number of aromatic organic compounds. These oil based compounds are eaten up by the bacteria as they utilize them as substrates for carrying out metabolism. These microorganisms occur in abundance in water bodies and soil and are effective in cleansing oil spills. With an increase in density of these microorganisms, the process of bioremediation is also accentuated. Other bacteria that help in bioremediation are Achromobacter, Flavobacterium, Acinetobacter, etc.
Chemical Method of Degradation
In this process, microorganisms, like bacteria and fungi (fungi used for assisting bioremediation is called mycoremediation) are once again employed but they show chemical action on the petroleum products. The hydrocarbons are rapidly oxidized by the enzyme oxygenase in presence of oxygen. This reaction forms the basis of bioremediation for oil spills. Bacteria and fungi are capable of hydroxylating the aromatic rings to form diols. These compounds are subsequently degraded and taken up by the microorganisms for aiding in proper functioning of the tricarboxylic acid cycle (TCA). When the process is successfully completed, it results in release of the carbon dioxide, water and other types of non-toxic compounds.
Use of Biostimulators or Accelerators
Biostimulators are added to soil and water to accelerate the rate of degradation. They are used when the depth of contamination is huge. Nutrients are added to increase the growth rate of oil-eating bacteria, by keeping the temperature, salinity, pH and other factors into account. The accelerating agents are sometimes chemical compounds that form a nutrient rich emulsion with water. Bacteria and fungi grow fast in such an environment, thereby eliminating the hydrocarbons rapidly. Various tests are done in the soil and water before mixing the biostimulating agents (hydrophobic chemicals, oleophilic compounds, etc.).
This process is also carried out for decontaminating wells and ponds as they are often polluted with hydrocarbons and heavy metals. Last but not the least, I must say that bioremediation is an excellent measure propounded by the 'Environment Protection Act' in saving both marine and terrestrial life forms.