UPSC 2017

QUES –  In the context of solving pollution problems, what is/are the advantage/advantages of bioremediation technique?

1 . It is a technique for cleaning up pollution by enhancing the same biodegradation process that occurs in nature.
2 . Any contaminant with heavy metals such as cadmium and lead can be readily and completely treated by bioremediation using microorganisms.
3 . Genetic engineering can be used to create microorganisms specifically designed for bioremediation.
Select the correct answer using the code given below:
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer – (c)

Bioremediation is the process of using organisms to neutralize or remove contamination from waste. This form of waste remediation uses no toxic chemicals, although it may use an organism that can be harmful under certain circumstances.

Thus bioremediation is a treatment that uses naturally occurring organisms to break down hazardous substances into less toxic or non toxic substances.

Significance of bioremediation

Bioremediation is important because –

1. It uses no chemicals – One of the issues with using man-made chemicals in the treatment and removal of contamination is that the chemicals eventually make it into the water supply. There were many chemicals used at the beginning of the waste management era that we now know were very harmful to plant, animal and human life once they reached the water supply.

2. It can allow waste to be recycled – Another major reason that bioremediation is preferred is that once the waste is treated and the contamination neutralized or removed, the waste itself can then be recycled. When chemical remediation types are used, the waste is still contaminated just with a less toxic substance and in general, cannot then enter into the recycle process. Bioremediation allows for more waste to be recycled while chemical methods still create waste that cannot be used and has to be stored somewhere.

Classes of Bioremediation

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Depending on general application of the organisms there are two classes of Bioremediation –

1 . In-situ – In situ refers to when contaminated waste is treated right at its point of origin. For example, there may be soil that is contaminated. Rather than remove the soil from its point of origin, it is treated right where it is. The benefit to in situ treatment is that it prevents the spread of contamination during the displacement and transport of the contaminated material.

2 . Ex-situ – Ex situ refers to treatment that occurs after the contaminated waste has been removed to a treatment area. To use soil as the example again, the soil may be removed and transported to an area where the bioremediation may be applied. The main advantage to this is it helps to contain and control the bioremediation products, as well as making the area that was contaminated available for use.

Types of Bioremediation

1. Phytoremediation – use of plants to remove contaminants. The plants are able to draw the contaminants into their structures and hold on to them, effectively removing them from soil or water.

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2. Bioventing – blowing air through soil to increase oxygen rates in the waste. This is an effective way to neutralize certain oxygen sensitive metals or chemicals.

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3. Bioleaching – removing metals from soil using living organisms. Certain types of organisms  draw  heavy metals and other contaminants and absorb them. One new approach was discovered when fish bones were found to attract and hold heavy metals such as lead and cadmium.

4. Landfarming – turning contaminated soil for aeration and sifting to remove contaminants, or deliberately depleting a soil of nitrogen to remove nitrogen based organisms.

5. Bioreactor – the use of specially designed containers to hold the waste while bioremediation occurs

6. Composting – containing waste so a natural decay and remediation process occurs.

7. Bioaugmentation – adding microbes and organisms to strengthen the same in waste to allow them to take over and decontaminate the area

8. Rhizofiltration – the use of plants to remove metals in water.

9. Biostimulation – the use of microbes designed to remove contamination applied in a medium to the waste.

Limitations of Bioremediation

There are some types of contamination that are very difficult to use bioremediation for. The two biggest concerns are:

1 . Cadmium
2 . Lead
Both of these are classified as heavy metals and are difficult to remove using microorganisms. A recent discovery about the absorption rate of fish bone has proving successful . In fact, bone seems to hold the clue for removing heavy metal contamination. Char is used to remove small amounts of zinc, lead and cadmium; and it is thought that the calcium in the fish bone is what makes it effective.