Bioremediation: Meaning | Need | Merits | Scope & Approaches

Bioremediation: Meaning | Need | Merits | Scope & Approaches

Meaning of Bioremediation

Bioremediation means “the use of living organisms (preferably microorganisms) for the removal of a pollutant from the biosphere”. It is a biological process to minimize unwanted environmental impact of the pollutants. Microorganisms have the ability to degrade, detoxify and even accumulate the harmful organic as well as inorganic compounds. Apart from microorganisms, higher plants also have the ability to remove such pollutants, primarily through their ability to accumulate these in their tissues.

Bioremediation has emerged recently as most ideal alternative, environment friendly and ecologically sound technology for removing pollutants from the environment, restoring contaminated sites, and preventing further pollution. This technology is way better when it is compared to physical or chemical processes; therefore the range of organisms to be used for pollution cleanup is expanding. Bioremediation forms a vital component of the green movement of maintaining the nature’s overall ecological balance. Bioremediation is the alliance of biological and engineering system for the remediation of undesirable chemical pollution. The objective of bioremediation is to exploit naturally occurring biodegradation processes for cleanup of the polluted environment.

Need and Scope of Bioremediation

Due to industrial revolution, human activities have resulted into the eventual release of large quantities of chemicals in the environment, either for agricultural and industrial purposes or accidentally by mishandling of chemicals. Remediation was earlier done by physical or chemical processes which are now substituted by biological and natural processes.

It is known that microorganisms are present in almost every part of the Earth and that they are capable of degrading and mineralizing a wide range of organic compounds. In bioremediation, microorganisms are used to breakdown organic compounds into less complex chemicals.

The most common microorganisms involved in biodegradation include aerobic bacteria, actinomycetes, cyanobacteria, anaerobic bacteria, fungi and algae.

Principle of bioremediation is natural attenuation, which means naturally occurring processes in the environment that act without human intervention to reduce the mass, toxicity, mobility, volume or concentration of contaminants in those media.

Merits / Advantages of Bioremediation

  • Bioremediation is a natural process and costs associated with remediation technologies are less expensive than physical or chemical processes.
  • Bioremediation is more environment friendly and ecologically sound and has the potential to be more socially acceptable when compared to physical or chemical processes such as thermal treatment, incineration, soil washing, chemical treatment or extraction processes, supercritical fluid oxidation and volatilization technologies.
  • In many cases bioremediation is a permanent solution to the contamination problem because the contaminant is completely destroyed or sequestered.
  • An additional advantage of bioremediation is that it can be relatively non-intrusive to the environment i.e. there is no waste accumulation after excavating, the contaminant is not transported form its location.
  • Bioremediation has application in the gas phase, in water phase and in soils and sediments.

Approaches to Bioremediation

Bioremediation technology is dependent on the abilities of microorganisms to degrade and detoxify organic and inorganic compounds. In simplest form of bioremediation, it does not involve any intervention at all and simply allows natural processes to reduce the concentration of the contaminant in the environment. This is usually referred to as natural attenuation or intrinsic bioremediation. Alternation or manipulation of physical or chemical properties of the contaminants in the environment is used to enhance the natural processes. This is referred to as enhanced bioremediation.

Many approaches are being used to effectively to catalyse bioremediation; sometimes the simple addition of a limiting nutrient is appropriate, while at other times microbial inoculum is needed.  In some situations it may be essential to add readily degradable substrates to foster co-metabolism of a contaminant or to drive to an environment to stimulate anaerobic degradation.  Sometimes, it may be necessary to add surfactants or other chemicals to increase the bio-availability of a contaminant.

Summing up all these, there are two fundamental approaches to enhance bioremediation:

  1. Biostimulation- It depends primarily on the modification of the environment.
  2. Bioaugmentation- It uses the addition of microbial cultures to increase biodegradation.

Now days, these two approaches are combined and microorganisms are introduced in conjugation with environmental modifications such as nutrient supplementation.

For bioremediation of polluted water and soil, the process can be carried out either in place, i.e. in situ bioremediation or after the contaminated material has been moved to some sort of contaminant reactor, i.e. ex situ bioremediation. In situ bioremediation is generally rather less expensive, but ex situ bioremediation is much faster that the additional cost of manipulating the contaminated material is overshadowed by the time saved.

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