• Bioremediation is the use of microorganisms (bacteria and fungi) to degrade the environmental contaminants into less toxic forms.
  • The microorganisms may be indigenous to a contaminated area or they may be isolated from elsewhere and brought to the contaminated site.
  • The process of bioremediation can be monitored indirectly by measuring the Oxidation Reduction Potential or redox in soil and groundwater, together with pH, temperature, oxygen content, electron acceptor/donor concentrations, and concentration of breakdown products (e.g. carbon dioxide)

In situ bioremediation

  • In situ — 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 the water table to increase groundwater oxygen concentrations and enhance the rate of biological degradation of contaminants by naturally occurring bacteria
  • Bioaugmentation: Microorganisms are imported to a contaminated site to enhance degradation process.

Using bioremediation techniques, TERI has developed a mixture of bacteria called ‘Oilzapper and Oilivorous-S’ 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.

Ex situ bioremediation

  • Ex situ — involves the removal of the 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 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 (soil, sediment, sludge) or water through an engineered containment system.
  • Composting: Composting is nature’s process of recycling decomposed organic materials into a rich soil known as compost.

Advantages and Disadvantages of bioremediation

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 all compounds are susceptible to rapid and complete degradation.
  • Biological processes are often highly specific.
  • It is difficult to extrapolate from bench and pilot-scale studies to full-scale field operations.
  • Bioremediation often takes longer time than other treatment process.

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