- Bioremediation is the use of microorganisms 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.
1. 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 a usd 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.
2. Ex situ bioremediation techniques
- 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 tiled until pollutants are degraded, the goal is to stimulate indigenous biodegradative miceooragmis and facilitate their aerobic degradation of contaminants.
- Biopiles- it is a hybrid of landfarming and composting. essentially , engineered cells are constructed as aerated compost 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.
- Composition- dealt earlier in solid waste management
Genetic engineering approaches
- Phytoremediation is use of plants to remove contaminants from soil and water
- phytoextraction/ phytoaccumulation is the process by which plants accumulate contaminants into the roots and above ground shoots or leaves.
- Phytotransformation or photodegradation refers to the uptake of organic contaminants from soil,sediment,orwater and their transformation to more stable,less toxic, less mobie from.
- 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.
- Photodegradation or rhizodegradation 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.
- Rhizofiltration is a water remediation technique that involves the uptake of contaminants by plant roots. Rhizofiltration is used to reduce contamination in natural wetlands and estuary areas.
- Is a form of bioremediation in which fungi are used to decontaminate the year.
- Is a similar process, using fungal mycelia to filter toxic waste and microorganism from water in soil.
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
Disadvantage of bioremediation
- Biodegradable is limited to these 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.