Previous Year Question
In the context of solving pollution problems, what is/are the advantage/advantages of bioremediation technique?
It is a technique for cleaning up pollution by enhancing the same biodegradation process that occurs in nature.
Any contaminant with heavy metals such as cadmium and lead can be readily and completely treated by bioremediation using microorganisms.
Genetic engineering can be used to create microorganisms specifically designed for bioremediation.
Select the correct answer using the code given below:
1 only
2 and 3 only
1 and 3 only
1, 2 and 3
Correct Answer: C
Detailed Solution
Bioremediation uses microorganisms, plants or their enzymes to degrade, transform, remove or immobilise pollutants present in the environment.
It can be used to treat contaminated soil, groundwater, surface water, sediments and industrial waste.
Statement 1 is correct: Microorganisms such as bacteria and fungi naturally biodegrade organic substances in nature.
Bioremediation can accelerate this natural process by providing oxygen, nutrients, electron acceptors or other favourable conditions.
The addition of nutrients or oxygen to the environment to enhance the activity of indigenous microorganisms is called biostimulation.
The addition of selected pollutant-degrading microorganisms to a contaminated site is called bioaugmentation.
Petroleum hydrocarbons, oil, certain solvents, pesticides and other biodegradable organic pollutants can be treated through bioremediation.
Under suitable conditions, microorganisms can transform certain organic pollutants into comparatively less toxic products such as carbon dioxide, water, salts and biomass.
Statement 2 is incorrect: Heavy metals such as cadmium and lead are basic chemical elements; therefore, microorganisms cannot biodegrade and destroy them.
Microorganisms may change the oxidation state of heavy metals or facilitate their adsorption, bioaccumulation, precipitation and immobilisation.
These processes may reduce the mobility or bioavailability of metals, but they do not ensure the ready and complete treatment of every heavy-metal contaminant.
Additional methods such as excavation, stabilisation, chemical treatment or phytoextraction may sometimes be required to treat heavy metals.
Statement 3 is correct: Genetic engineering can develop genes or metabolic pathways in microorganisms that assist in the degradation or transformation of specific pollutants.
The environmental use of genetically engineered microorganisms requires an assessment of biosafety, ecological effects, transfer of genetic material and effective containment.
Bioremediation can be less expensive and less environmentally disruptive than conventional physical or chemical treatments.
Its effectiveness depends on the nature of the contaminant, temperature, pH, moisture, oxygen, nutrients and the availability of the contaminant to microorganisms.