- In order to clean up a contaminated location, bioremediation refers to the utilisation of microorganisms that are either naturally existing or intentionally introduced.
- It is a method for detoxifying pollutants in soil and other settings that primarily makes use of microbes, but also plants and microbial or plant enzymes
- Biodegradation, which is the term for the partial and occasionally complete transformation or detoxification of pollutants by microbes and plants, is an element of the notion.
- By adding nutrients, carbon sources, or electron donors to the native microorganisms (bacteria or fungi) (biostimulation, biorestoration), or by adding an enriched culture of microorganisms that have particular properties that allow them to degrade the desired contaminant at a faster rate (bioaugmentation), the process of bioremediation increases the rate of the natural microbial degradation of contaminants.
Table of Contents
- Objective of Bioremediation
- Principle of Bioremediation
- Categories of Bioremediation
- Types of Bioremediation Methods
- Methods of Bioremediation
- Applications of Bioremediation
- Advantages of Bioremediation
- Limitations and Concerns of Bioremediation
Objective of Bioremediation
- In order to comply with regulatory agency restrictions, bioremediation must at the very least lower pollutant levels to undetectable, harmless, or acceptable levels. Ideally, organopollutants should be entirely mineralized to carbon dioxide.
Principle of Bioremediation
- In order to do bioremediation, it is necessary to promote the development of certain bacteria that eat and produce energy from pollutants like oil, solvents, and pesticides.
- These microorganisms devour the pollutants and break them down into innocuous gases like carbon dioxide and tiny quantities of water.
- In order for bioremediation to be effective, the correct temperature, nutrition, and food must be present; otherwise, the removal of toxins may take significantly longer.
- If the environment is unsuitable for bioremediation, it can be made more suitable by introducing "amendments" such as molasses, vegetable oil, or even just air.
- These modifications produce the ideal environment for microorganisms to thrive and finish the bioremediation process.
- The bioremediation procedure might take a few months to many years.
- The amount of time needed varies depending on factors including the size of the polluted region, the amount of pollutants present, environmental factors like soil density and temperature, and whether bioremediation will occur in situ or ex-situ.
Categories of Bioremediation
Two categories of biological remediation exist:
Microbial Remediation
- The capacity of microorganisms to degrade a wide variety of organic molecules and absorb inorganic chemicals is well documented. At the moment, bioremediation procedures include the employment of bacteria to clean up pollutants.
- Toxic and other pollutants can be removed from the environment using a variety of microbial systems, including bacteria, fungi, yeasts, and actinomycetes.
- Microorganisms are abundant, easily described, incredibly diversified, all-pervasive, and capable of using a wide range of toxic substances as a source of nutrition.
- They may be used both in situ and ex-situ settings, and they can also clean up in a variety of harsh environmental situations.
- Even though a variety of microorganisms may break down crude oil found in soil, it has been shown that using a mix culture method rather than pure cultures in bioremediation is more advantageous since it demonstrates the synergistic interactions.
- For the removal of petroleum hydrocarbon pollutants from soil, several bacteria can be utilised.
- Pseudomonas, Aeromonas, Moraxella, Beijerinckia, Flavobacteria, Chromobacteria, Nocardia, Corynebacteria, Acinetobacter, Mycobactena, Modococci, Streptomyces, Bacili, Arthrobacter, Aeromonas, and Cyanobacteria are among the bacteria that may break down significant pollutants.
Phytoremediation
- A bioremediation technique called phytoremediation employs diverse plant species to transport, stabilize, and/or eliminate pollutants in soil and groundwater.
- The mechanisms of phytoremediation come in many different forms.
1. Rhizosphere biodegradation: In this process, the plant releases organic compounds through its roots, feeding soil microbes with nutrition. The microbes accelerate biological decay.
2. Phyto-stabilization: Instead of degrading impurities throughout this process, the plant's chemical byproducts immobilise them.
3. Phyto-accumulation (also called phytoextraction): The pollutants are absorbed by plant roots during this process, along with other nutrients and water. The contaminated mass is not removed; instead, it becomes part of the plant's leaves and branches. This technique is mostly used to metal-containing trash.
4. Hydroponic Systems for Treating Water Streams (Rhizofiltration): In contrast to phytoaccumulation, rhizofiltration employs plants that are grown in greenhouses with their roots submerged in water. Ex-situ groundwater remediation may be done using this growth technique. In order to irrigate these plants, groundwater is pumped to the surface. An artificial soil media, like as sand blended with perlite or vermiculite, is typically used in hydroponic systems. The roots are removed and discarded as soon as they are completely saturated with pollutants.
5. Phyto-volatilization: In this procedure, plants absorb contaminated water that contains organic substances and then expel those substances into the atmosphere through their leaves.
6. Phyto-degradation: Plants really metabolise and eliminate pollutants inside plant tissues during this process.
7. Hydraulic Control: By restricting the circulation of groundwater during this process, trees indirectly remediate. When a tree's roots descend below the water table and form a massive root mass that absorbs a lot of water, they operate as natural pumps. A cottonwood tree may absorb up to 350 gallons of water per day, whereas a poplar tree can extract 30 gallons of water from the ground each day.
Types of Bioremediation Methods
- Natural attenuation or intrinsic bioremediation: Without outside intervention, bioremediation happens naturally.
- Biostimulation: To boost the bioavailability within the medium, fertilisers are added to encourage bioremediation.
Technologies can be generally classified as in situ or ex-situ.
- In situ bioremediation:It entails cleaning up the site's contamination.
- Ex situ bioremediation: It entails taking the contaminated material somewhere else to be treated.
Methods of Bioremediation
Examples of bioremediation-related technologies include the following:
- Phytoremediation
- Bioventing
- Bioleaching
- Land-farming
- Bioreactor
- Composting
- Bioaugmentation
- Rhizo-filtration
- Biostimulation
Applications of Bioremediation
- Metals, radionuclides, pesticides, explosives, fuels, volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs) can all be remedied via bioremediation.
- Perchlorate, a pollutant that has been demonstrated to be persistent in surface and groundwater systems, is being remedied, and research is being done to understand the function of phytoremediation in this process.
- It might be used to remove pollutants from soil and groundwater.
- Chelating agents are occasionally employed to render radioactive pollutants suitable for plant uptake.
Advantages of Bioremediation
- In comparison to other cleanup techniques, bioremediation provides a variety of benefits.
- It is a comparatively green approach that harms ecosystems less because it simply employs natural processes.
- Since amendments and bacteria may be injected underground to clean up toxins in groundwater and soil, it frequently takes place underground and hence does not significantly impact adjacent populations.
- Due to the fact that toxins and pollutants are transformed into water and safe gases like carbon dioxide throughout the bioremediation process, there aren't many dangerous byproducts produced.
- Because it requires less labour and equipment than other cleanup techniques, bioremediation is more affordable.
- The precise bacteria required to break down the contaminant are encouraged by choosing the limiting element needed to stimulate their development, and bioremediation may be adjusted to the demands of the contaminated location in question.
Limitations and Concerns of Bioremediation
- It is not always possible to predict the toxicity and bioavailability of biodegradation products.
- By-products of degradation may be bio-accumulated in animals or mobilised in groundwater.
- To make sure that plant products and droppings do not introduce dangerous or harmful substances into the food chain, further study is required to establish the destiny of different molecules in the metabolic cycle of plants.
- When leaves fall in the autumn or when firewood or mulch made from trees is used, scientists need to determine whether pollutants that accumulate in leaves and wood of trees are discharged.
- If harvested plants have large quantities of heavy metals, disposal may be problematic.
- Treatment is restricted by the depth of the pollutants. Generally speaking, it only occurs in shallow soils, streams, and groundwater.
- Typically, shallow soil, streams, and groundwater pollution, as well as locations with lower pollutant concentrations, are the only places where phytoremediation is used.
- Depending on the environment, phytoremediation may have seasonal success. Its efficiency will also be impacted by other meteorological circumstances.
- The establishment of a chosen plant community is essential for cleanup to be successful. The introduction of new plant species may have far-reaching ecological effects. It has to be observed and examined beforehand.
- Plants may perish if pollutant concentrations are too high.
- Some phytoremediation moves pollution from one medium to another (like soil to air).
- For heavily sorbed pollutants like polychlorinated biphenyls (PCBs), phytoremediation is ineffective.
- A sizable amount of land surface is needed for phytoremediation.
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