Bioremediation

Bioremediation is a waste management technique that involves the use of organisms to remove or neutralize pollutants from a contaminated site. According to the EPA, bioremediation is a “treatment that uses naturally occurring organisms to break down hazardous substances into less toxic or non toxic substances”.
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 encourage the growth of the pollution-eating microbes within the medium (biostimulation).

How does bioremediation work:-
For the process of bioremediation, it is necessary that microorganisms should be healthy and active so that they can perform their duty efficiently. It is not necessary that all the microorganisms detoxify the same contaminants and toxins but for different toxins there are different microorganisms because there are different habitats for different organisms.

Bioremediation can take place in two conditions that are aerobic and anaerobic conditions. In anaerobic condition, microbes need oxygen to perform their duty. If they will get oxygen in sufficient amount they will be able to easily convert the contaminants and toxins into water and carbon. In anaerobic conditions, microbes do the activity in the absence of oxygen. Chemical compounds which are present in the soil can be decomposed by bacteria under anaerobic conditions. As a result energy produces which is used by the microbes.

Types of Bioremediation:-
There are three types of bioremediation and all are used to remove toxic substances and contaminants from the environment whether they are rivers or crude oils.

Biostimulation:-
Biostimulation is the method in which bacteria are motivated to start the process of bioremediation. In this method, first he experts release nutrients and other important substances in the soil where there is need or removing the contaminants. These are in the form of gas or liquid. It increases the growth of microbes in that area. As a result bacteria and other microorganisms remove the contaminants quickly and efficiently.

Bioaugmentation:-
In some processes of bioremediation, there are some special sites where microorganisms are needed to remove the contaminants for example municipal wastewater. Bioaugmentation is used for that purpose. But unfortunately this process is not very successful as it is difficult to control the growth of microorganisms to remove the particular contaminant.

Intrinsic Bioremediation:-
The process of intrinsic bioremediation takes place in soil and water because these two places are always full of contaminants and toxins. This process is also called as natural attenuation. It also means use of the microorganisms to remove the harmful substances from soil and water. Especially those sites are treated with this method, which are underground, for example underground petroleum tanks. It is difficult to know if there is a leakage in the petroleum pipes. Contaminants and toxins find their way to enter in these sites and create harmful effects on the petrol. Therefore, only microorganisms can destroy the toxins and clean the tanks. Great care should be taken if some leakage occurs in the petroleum tanks or pipes because it may damage the human health.



 1. Microbial bioremediation

Bioremediation of organic compounds is primarily based on either microorganisms naturally present at the sites, or on microbial inoculants developed in the laboratory and introduced at the site. Certain bacterial, fungal and algal species are capable of accumulating some toxic inorganic contaminants as well. However, there is no cost-effective method of removing these microorganisms from the soil after they have sequestered the inorganic ions. Therefore, bioremediation of inorganic contaminants is primarily based on suitable plant species.

E.g. oil spills are known to cause fire, ground water pollution due to percolation, death of marine life and air pollution on evaporation. Earlier saw dust was used to treat oil spills. However, with the advent of bioremediation techniques, oil-eating bacteria have been used to treat the oil spills in a much more efficient and cost effective way.

E.g. Pseudomonas sp

2. Phytoremediation

Phytoremediation is the use of green plants and their associated microorganisms, soil amendments. And agronomic practices to remove contain or render harmless environmental contaminants. Plants were first used in Germany for sewage treatment over 300 years ago and since then their use has become rather common. Plants are also used to decontaminate soils polluted by organic wastes. For example, carrots are used to absorb DDT; these carrots are harvested, air dried and incinerated to destroy the DDT.

Plant roots absorb organic compounds and perform remediation by accumulating the organics in plant tissues, translocation to leaf and then volatilization or by metabolizing and degrading the organic compounds intrinsically using enzymes.

Plants remove inorganic contaminants wither by contaminant volatilization or by metal accumulation. Volatilization is a useful process for recovering mercury however the latter method is preferred for other inorganic compounds. The plants used in bioremediation have to be appropriately disposed.