Arkajit Ganguly, Assistant Professor, Department of Microbiology, Brindavan College, Bangalore -94.
"Remediate" means to solve a problem, and "bio-remediate" means to use biological organisms to solve an environmental problem related to contaminated soil or groundwater.
The rapid expansion and increasing sophistication of the different industries in the past century has meant that there has been an increasing amount and complexity of toxic waste which pollute the environment. Bioremediation provides a technique for cleaning up environmental pollution by enhancing the same biodegradation processes that occur in nature. Depending on the site and its contaminants, bioremediation may be safer and less expensive than alternative solutions such as incineration or land filling of the contaminated materials. Bioremediation uses microorganisms (both bacteria and fungi) to degrade organic contaminants in soil, groundwater, sludge, and solids. The microorganisms break down contaminants by using them as an energy source or co-metabolizing them with an energy source.
There are three types of bioremediation strategies involving microorganisms:
1) Natural attenuation – In some cases, natural populations of microorganisms adapt to the contaminant conditions and are able to convert the contaminants to non-hazardous end products
2) Biostimulation – In some cases, natural populations can be stimulated to degrade contaminants (e.g. Addition of nutrients to enhance microbial growth)
3) Bioaugmentation – In some cases it is necessary to add the microbial organisms that are capable of degrading the contaminant rapidly.
Bioremediation may be conducted in situ or ex situ. In situ processes treat soil and groundwater in place, without removal or transportation offsite. This approach may be advantageous since the costs of materials handling and some environmental impacts may be reduced. However, in situ processes may be limited by the ability to control or manipulate the physical and chemical environment during bioremediation. Ex situ processes, on the other hand, involve the removal of the contaminated media to a treatment area Still there are various other factors that affect the process of bioremediation. These include contaminant concentration, contaminant bioavailability, pH, temperature, nutrients, etc.
Though bioremediation provides a good cleanup strategy for some types of pollution, but as expected, it will not work in all cases. For example, bioremediation may not provide a feasible strategy at sites with high concentrations of chemicals that are toxic to most microorganisms. The success of a bioremediation of a contaminated site highly depends on characterization and monitoring completed before and during its implementation.