- Definition Bioremediation refers to the use of natural or specifically introduced microorganisms to consume and break down environmental pollutants to remediate old pollution.
- It is a process that mainly uses microorganisms but also plants or microbial or plant enzymes to detoxify pollutants in soil and other environments.
- The concept includes biodegradation, which refers to the partial and sometimes complete conversion or detoxification of pollutants by microorganisms and plants.
- The bioremediation process improves the natural microbial degradation rate of pollutants by supplementing native microorganisms (bacteria or fungi) with nutrients, carbon sources, or electron donors (bio-stimulation, bio-restoration) or by adding an enriched culture of microorganisms with specific properties. which enable them to break down the desired pollutant more quickly (bioaugmentation).
Goal of bioremediation
The aim of bioremediation is at least to reduce pollutant concentrations to undetectable, non-toxic, or acceptable levels, i.e.
- Bioremediation is based on stimulating the growth of certain microbes that use pollutants such as oil, solvents, and pesticides as a source of food and energy.
- These microbes consume the pollutants and turn them into small amounts of water and harmless gases like carbon dioxide.
- Effective bioremediation requires a combination of the right diet, nutrients, and temperature; Otherwise, the pollutant remediation can take much longer.
- If conditions are not favorable for bioremediation, they can be improved by adding “supplements” to the environment such as molasses, vegetable oil, or simply air.
- These changes create the optimal conditions for microbes to thrive and complete the biological remediation process.
- The bioremediation process can take anywhere from a few months to several years.
- The time required depends on variables such as the size of the contaminated area, the pollutant concentration, conditions such as temperature and soil density, and whether the bioremediation is carried out in situ or ex-situ.
Biological remediation can be divided into two types: microbial remediation and phytoremediation.
- Microorganisms are known for their ability to break down a wide variety of organic compounds and absorb inorganic substances. Microbes are currently used to cleanse the treatment of contaminants in processes known as bioremediation.
- Various microbial systems such as bacteria, fungi, yeast, and actinomycetes can be used to remove toxic and other contaminants from the environment.
- Microorganisms are readily available, quickly characterized, very diverse, ubiquitous, and can use many harmful elements as a source of nutrients.
- They can be applied both in situ and ex-situ; In addition, these entities can eliminate many extreme environmental conditions.
- Although many microorganisms are able to degrade crude oil present in the soil, it has been shown that it is more advantageous to use a mixed culture approach than pure cultures in biological remediation, as it shows synergistic interactions.
- Various bacteria can be used to remove petroleum hydrocarbon contaminants from the soil.
- Bacteria that can break down major contaminants include Pseudomonas, Aeromonas, Moraxella, Beijerinckia, Flavobacteria, Chrobacteria, Nocardia, Corynebacteria, Acinetobacter, Mycobacteria, Modococci, Streptomyces, Bacilli, Arthrobacter, Aeromonas, and Cyanobacteria.
Phytoremediation is a biological remediation process in which various plant species are used to remove, transfer, stabilize and/or destroy pollutants in soil and groundwater.
There are several types of phytoremediation mechanisms.
- Biodegradation of the rhizosphere. The plant releases natural substances through its roots and supplies the microorganisms in the soil with nutrients. Microorganisms promote biological degradation.
- Phytostabilization: In this process, the chemical compounds produced by the plant immobilize the pollutants instead of breaking them down.
- Phytoaccumulation (also called phytoextraction). The roots of the plants absorb the pollutants along with other nutrients and water. The contaminating mass is not destroyed but ends up in the shoots and leaves of the plant. This process is mainly used for waste-containing metal.
- Hydroponic systems for the treatment of water currents (rhizofiltration). Rhizofiltration is similar to phytoaccumulation, but the plants used for cleaning are grown in greenhouses with their roots in the water. This cultivation method can be used for ex-situ groundwater treatment. That is, groundwater is pumped to the surface to irrigate these plants. Hydroponic systems typically use an artificial soil medium, such as sand mixed with perlite or vermiculite. When the roots are saturated with impurities, they are harvested and disposed of.
- Phytovolatilization: Plants absorb water with organic pollutants and release it into the air through their leaves.
- Phyto-degradation. In this process, plants actually metabolize and destroy pollutants in plant tissue.
- Hydraulic steering. The trees are recovered indirectly by controlling the movement of the groundwater. Trees act as natural pumps when their roots sink to the water table and form a dense root mass that absorbs large amounts of water. A popular, for example, draws 30 liters of water from the ground every day, and the poplar can absorb up to 350 liters a day.
What are 2 types of bioremediation?
- Natural attenuation or intrinsic bioremediation: Bioremediation occurs on its own without adding anything.
- Biostimulation: bioremediation is stimulated by adding fertilizers to increase bioavailability in the medium.
Technologies can basically be classified as in situ or ex-situ.
- In-situ bioremediation: it consists of treating the contaminated material on-site.
- Ex-situ bioremediation: includes the removal of contaminated material that needs to be treated elsewhere.
Some examples of bioremediation-related technologies are:
- Bioremediation is used for the remediation of metals, radionuclides, pesticides, explosives, fuels, volatile organic compounds (VOC), and semi-volatile organic compounds (SVOC).
- Research is being carried out to understand the role of phytoremediation in the remediation of perchlorate, a pollutant that has been shown to be persistent in surface and groundwater systems.
- It can be used to clean pollutants in soil and groundwater.
- In the case of radioactive materials, chelating agents are sometimes used to make the pollutants susceptible to uptake by plants.
Applications of bioremediation
Bioremediation has a number of advantages over other cleansing methods.
- Since only natural processes are used, it is a relatively environmentally friendly method that is less damaging to ecosystems.
- It often takes place underground as additives and microbes can be pumped underground to remove contaminants in the groundwater and in the soil; Therefore, it does not cause much disruption in the surrounding communities.
- The bioremediation process creates few harmful by-products as pollutants and pollutants are converted into water and harmless gases like carbon dioxide.
- Bioremediations are cheaper than most cleaning methods because they don’t require a lot of equipment or labor.
- Bioremediation can be tailored to the needs of the particular contaminated site, and the specific microbes required to break down the pollutant are encouraged by choosing the limiting factor necessary to promote its growth.
Limitations and Concerns of Bioremediation
- The toxicity and bioavailability of biodegradation products are not always known.
- Degradation products can be mobilized in the groundwater or bioaccumulated in animals.
- More research is needed to determine the fate of various compounds in the metabolic cycle of plants to ensure that plant excretions and products do not add toxic or harmful chemicals to the food chain.
- Scientists need to determine if pollutants that build up in tree leaves and wood are released when the foliage falls in autumn or when firewood or mulch is used from trees.
- Removal of harvested plants can be a problem if they contain high levels of heavy metals.
- The depth of the contamination limits the treatment. In most cases, it is limited to shallow soils, streams, and groundwater.
- In general, the use of phytoremediation is limited to locations with lower pollutant concentrations and contamination in shallow soils, streams and groundwater.
- The success of phytoremediation can depend on the season, depending on the location. Other climatic factors also influence the effectiveness.
- The success of the renovation depends on the establishment of a selected plant community. The introduction of new plant species can have far-reaching ecological effects. It must be studied and monitored in advance.
- If the pollutant concentration is too high, plants can die.
- Some phytoremediation transfers contamination through the medium (e.g. from the soil to the air).
- Phytoremediation is not effective for highly absorbed pollutants such as polychlorinated biphenyls (PCB).
- Phytoremediation requires a large area for rehabilitation.
Definition bioremediation, Goal of bioremediation, Bioremediation categories