Safdar Gazi
“Bioremediation is nature’s own way of healing the earth. It harness the power of microorganisms to restore balance and cleanse our environment.” (Aubaid Akhoon)
Intensification of agriculture and manufacturing industries has results in increased release of a wide range of xenobiotic compounds to the environment. Excess loading of hazards waste has led to scarcity of clean water and disturbances of soil thus limiting crop production.
Bioremediation uses biological agents mainly microorganisms i.e. yeast, fungi or bacteria to clean up the contaminated soil and water. This technology relies on promoting the growth of specific micro flora or microbial consortia that are indigenous to the contaminated sites that are able to perform desired activities. Establishment of such microbial consortia can be done in several ways e.g by promoting growth through addition of nutrients, by adding terminal electron acceptor or by controlling moisture and temperature conditions. In bioremediation processes, microorganisms use the contaminants as nutrients or energy sources.
The population explosion in the world has resulted in an increase in the area of polluted soil and water. As the number of people continues increasing day by day it also brings with it a growing pressure on our natural resources i.e air, water and land resources . in order to outfit to the demands of the people the rapid expansion of industries, food, healthcare, vehicles etc. But it difficult to maintain the quality of life with all these new developments. Which are unfavorable to the environment in which we live, if proper management is not applied. In nature there are various fungi, bacteria and microorganisms that are constantly at work to break down organic compounds but the question arises when pollution occur, who will do this clean up? Since the quality of life is inextricably linked to the overall quality of the environment, global attention has focused on ways to sustain and preserve the environment. This endeavor is possible by involving biotechnology. The type of contaminants that environmental biotechnology investigators has expertise with include chlorinated solvents, petroleum hydrocarbons, ketones, TNT. Several workers have described various application of microorganism in the bioremediation of oil pollution with encouraging results.`
Bioremediton strategies
In-situ bioremediation techniques
It involves treatment of the contaminated material at the site.
Bioventing: Supply of air and nutrients through wells to contaminated soil to stimulate the growth of indigenous bacteria. It is used for simple hydrocarbons and can be used where the contamination is deep under the surface.
Biosparging: Injection of air under pressure below water table to increase ground water oxygen concentration and enhance the rate of biological degradation of contaminants by naturally occurring bacteria.
Bioaugmentation: Microorganisms are imported to contaminated site to enhance degradation process.
Ex-situ bioremediation techniques
Ex-situ involves the removal of contaminated material to be treated elsewhere.
Land-farming: Contaminated soil is excavated and spread over a prepared bed and periodically tilled until pollutants are degraded. The goal is to stimulate the indigenous biodegradative microorganisms and facilitate their aerobic degradation of contaminants.
Biopiles: It is a hybrid of land farming and composting. Essentially, engineered cells are constructed as aerated composted piles. Typically used for treatment of surface contamination with petroleum hydrocarbons.
Bioreactors: It involves the processing of contaminated solid material such as soil, sediment, sludge or water through an engineered containment system.
Composting
Using bioremediation techniques, TERI has developed a mixture of bacteria called oil –zapper which degrades the pollutants of oil-contaminated sites, leaving behind no harmful residues. This technique is not only environment friendly, but also highly cost-effective.
Genetic engineering approaches
Phytoremediation
Phytoremediation is use of plants to remove contaminants from soil and water.
Types
Phytoextraction /phytoaccumulation is the process by which plants accumulate contaminants into the roots and above ground shoots or leaves
Phytotransformation or phytodegredation refers to the uptake of organic contaminants from soil, sediments or water and their transformation to more stable, less toxic, less mobile form.
Phytostabilization is a technique in which plants reduce the mobility and migration of contaminated soil. Leachable constituents are adsorbed and bound into the plant structure so that they form unstable mass of plant from which the contaminants will not re-enter the environment.
Rhizodegradtion is the breakdown of contaminants through the activity existing in the rhizosphere. This activity is due to the presence of proteins and enzymes produced by the plants or by soil organisms such as bacteria, yeast, and fungi.
Nature is the ultimate bioremediation expert. It has been fine-tuning its methods for millions of years, and now we have the opportunity to learn from its wisdom” (Aubaid Akhoon)
Advantages of bioremediation
Useful for the complete destruction of a wide variety of contaminants.
The complete destruction of target pollutants is possible.
Less expensive environment friendly.
Disadvantages of bioremediation
Bioremediation is limited to those compounds that are biodegradable.
Not only compounds are susceptible to rapid and complete degradation.
Biological processes are often highly specific.
Bioremedation often takes longer time than other treatment process.
‘Bioremediation reminds us that even in the face of environmental degradation, there is always a chance for renewal and regeneration.” (Aubaid Akhoon)
(The author is M.Sc Botany and is presently working as Botany Faculty at DD TARGET PMT and can be reached at [email protected])
