BIOREMEDIATION AND ITS TECHNIQUES
BIOREMEDIATION AND ITS TECHNIQUES
- It refers to the cleaning of environment with the help of living organisms. Living organisms range from microorganisms to different species of plants.
- For example, bacteria help in the decomposition of organic waste.
- Certain plant species such as mustard helps in the absorption of poisonous elements such as selenium.
- Bioremediation usually takes a longer time period.
- However, bioremediation effectively discriminates between pollutants and the required nutrients.
Strategies of Bioremediation
In Situ Bioremediation Techniques
- These techniques refer to the treatment of waste at its site.
- These techniques not only assist in the degradation of adsorbed fuel residuals, but also assist in the degradation of volatile organic compounds.
- In situ bioremediation techniques include biosparging, bioventing and bioaugmentation.
- Biosparging is an in situ remediation technology that uses indigenous microorganisms to biodegrade organic constituents in the saturated zone.
- In biosparging, air (or oxygen) and nutrients are injected at high pressure to increase the biological activity of the indigenous microorganisms and enhance their decomposition activity.
- Bioventing is an in situ remediation technology that uses microorganisms to biodegrade organic constituents adsorbed in soils in the unsaturated zone.
- Bioventing enhances the activity of indigenous bacteria and simulates the natural in situ biodegradation of hydrocarbons in soil by inducing the flow of air or oxygen at low pressure into the unsaturated zone, and if necessary, adds nutrients.
- In conventional bioventing systems, oxygen is delivered by an electric blower to subsurface wells.
- Saturated zone requires injection of air and nutrients at high pressure and unsaturated zone requires injection of air and nutrients at low pressure.
- Bioaugmentation is a technique, where microorganisms are imported to a contaminated site to carry out degradation of organic waste. For instance, oil zapper (explained earlier).
Ex Situ Bioremediation Techniques
- Ex situ refers to the transfer of contaminated material for treatment to some other site.
- Ex situ bioremediation techniques include land farming and biopile.
- In land farming, the contaminated soil is spread over a prepared bed.
- The soil is periodically tilled to stimulate the growth of micro-organisms for the degradation of organic waste.
- Biopile is a hybrid of land farming and composting.
- Excavated soils are spread over a prepared bed, formed into compost piles and enclosed for treatment.
- Moisture, heat, nutrients, oxygen, and pH are controlled to enhance biodegradation. An irrigation/nutrient system is used to pass air and nutrients through the soil.
- Soil piles can be up to the height of 20 feet. They may be covered with plastic to control runoff, evaporation and to promote solar heating.
- Treatment time is typically three to six months, after which the excavated material is either returned to its original location or disposed off.
- The treatment area is generally covered or contained with an impermeable lining to minimise the risk of contaminants leaching into the uncontaminated soil.
- It means the use of plants to remove contaminants from soil and water.
- Neem plant is used for phytoremediation as it absorbs poisonous elements and reduces the growth of harmful microorganisms.
- It involves the use of fungus such as mycelia to decontaminate an area.
- Green muffler refers to the plantation of 5-6 rows, around populated areas like societies or housing schemes near highways, of dense trees to reduce noise pollution.
- It filters out the noise and doesn’t let it reach the populated areas.
- A muffler (silencer in many non-US English speaking countries) is a device for decreasing the amount of noise emitted by the exhaust of an internal combustion engine.
Uses of Biological Processes for the Extraction of Natural Resources
Biological processes can be used not just for remedial actions, but also for the extraction of useful natural resources as listed below:
- Biomining is a broad term that describes the extraction of metals from their ores using microbiological technology.
- Bioleaching is a sub type of biomining. It is widely used as extractive metallurgy technique which converts metal into soluble salts in aqueous media.
- Biosorption is a property of certain types of inactive, dead, microbial biomass to bind and concentrate heavy metals from even very dilute aqueous solutions.
- Phytomining is an approach, in which mining is done with the help of plants. For instance, some plants absorb copper compounds through their roots.
- As a result, copper compounds remain concentrated in their roots. The plants can be burned to produce an ash that contains copper.
- Phytoextraction is a subprocess of phytoremediation in which plants remove dangerous elements or compounds from soil or water, mostly heavy metals, metals that have a high density and may be toxic to organisms even at relatively low concentrations.