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What is Bioremediation Process and its Types
Use of biological organisms, such as bacteria, fungi (usually) and plants (sometimes), to reduce or eliminate toxic pollutants from contaminated sites by degradation, assimilation or transpiration in the atmosphere is called bioremediation. Degradation is the mode of elimination mostly in case of organic compounds, while heavy metals are assimilated.

1. Microbial bioremediation

Bioremediation of organic compounds is primarily based on either microorganisms naturally present at the sites, or on microbial inoculants developed in the laboratory and introduced at the site. Certain bacterial, fungal and algal species are capable of accumulating some toxic inorganic contaminants as well. However, there is no cost-effective method of removing these microorganisms from the soil after they have sequestered the inorganic ions. Therefore, bioremediation of inorganic contaminants is primarily based on suitable plant species.

E.g. oil spills are known to cause fire, ground water pollution due to percolation, death of marine life and air pollution on evaporation. Earlier saw dust was used to treat oil spills. However, with the advent of bioremediation techniques, oil-eating bacteria have been used to treat the oil spills in a much more efficient and cost effective way.

E.g. Pseudomonas sp

2. Phytoremediation

Phytoremediation is the use of green plants and their associated microorganisms, soil amendments. And agronomic practices to remove contain or render harmless environmental contaminants. Plants were first used in Germany for sewage treatment over 300 years ago and since then their use has become rather common. Plants are also used to decontaminate soils polluted by organic wastes. For example, carrots are used to absorb DDT; these carrots are harvested, air dried and incinerated to destroy the DDT.

Plant roots absorb organic compounds and perform remediation by accumulating the organics in plant tissues, translocation to leaf and then volatilization or by metabolizing and degrading the organic compounds intrinsically using enzymes.

Plants remove inorganic contaminants wither by contaminant volatilization or by metal accumulation. Volatilization is a useful process for recovering mercury however the latter method is preferred for other inorganic compounds. The plants used in bioremediation have to be appropriately disposed.

E.g. A. thaliana converts volatile Hg to Hg (O)
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Thanks for sharing such an interesting and informative post. I want to add few more lines in that Bioremediation does not solely depend on microorganisms. Bioremediation is the process of utilizing biological means to eliminate toxic wastes from the environment. Phytoremediation is a bioremediation involving plants. Bioremediation can be carried out using live, dead or resting cells of microorganisms. Contaminated soil recovery and management of polluted environment can be successfully handled by bioremediation process.

Since, bioremediation is a flourishing and effective cleaning mechanism for polluted environment it is in use in many places around the world with varying degree of success. This results in strong scientific growth of the process.

Bioremediation is based on two major techniques: biodegradation and biosorption i.e. either the pollutant is degraded to a less polluting substance so that it can enter easily into the biogeochemical cycle or it is absorbed within the body of the biological substances used. So it is clear that biodegradation is metabolism dependent, whereas biosorption is independent of metabolism of the cells involved.

Bioremediation came up as a solution for several environmental pollution issues like landfill stabilization, endocrine disrupters, mixed waste biotreatment and biological carbon sequestration specially using aerobic and anaerobic bacteria and fungi.

Bioremediation has capacity to detoxify effluents and solid wastes at low cost with less impact on the environment. No doubt it is coming up as an attractive alternative to conventional cleaning techniques. Though the method is not very complex, still it needs enough knowledge and experience to successfully set up a bioremediation plant.

Proper use can make bioremediation a economically favorable treatment for cleaning certain oil-contaminated environments. But there are certain constraints. Spilled oil cannot be treated in open environment using Bioaugmentation where the addition of nutrients gives similar results. But in confined spaces Bioaugmentation works better. Addition of nutrients along with bioremediation can be a potent alternative in handling oil-contaminated coasts. This process can be used both as a primary as well as secondary (after conventional method) strategy to counter oil-spill, depending on the nature and location of the spill i.e. whether to be cleaned immediately or not. Efficiency of biostimulation is also highly site-specific and depends on the factors like availability of oxygen and nutrients. The process works better when oxygen is not a limiting factor. In anaerobic situations addition of nutrients often has very less impact on oil biodegradation. The choice of nutrients is also important and depends on the nature of oil spills.

Nevertheless bioremediation possess a bright future in cleaning our environment and thus demand thrust and more energy as well as investments for future studies and successful scientific implementation of the process.
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Phytoremediation is another form of bioremediation involving plants. In recent times an increasing trend in land, surface and groundwater contamination from industrial and agricultural activities is becoming a major concern. Toxic environmental pollutants, including radionuclides, heavy metals, pesticides in soil, surface and ground water possess a major threat to the ecosystems. Conventional remediation practices of contaminated sites are often not useful due to limited potential, applicability to limited areas and huge cost. Moreover, these conventional techniques destroy the microenvironment often making the soil unsuitable for agriculture and infertile. Therefore, there is an emerging need to develop environmentally sound technologies (ESTs) considering the probable end use of the remediated site.
Let’s have a quick look at the Phytoremediation process
Phytoremediation is the process of removal; contaminated sites with plants alleviate environmental problems in a more ecofriendly manner.
It is a cost effective cleanup technique driven by solar energy, mostly useful in treating a wide range of environmental contaminants without generating toxic sludge.
Phytoremediation technique efficiently uses plant through their biological, chemical or physical processes for the removal, detoxification and/or immobilization of toxic contaminants in water soil and sediments. Plant systems are uniquely equipped with remarkable ability to adsorb along with transport systems that selectively takes up contaminants from water or soil. Growing plants are used in the process of phytoremediation at a contaminated site for a required period of growth to facilitate immobilisation, binding or detoxification of the pollutants. There are various ways that plants are used to remediate polluted sites. Plants have the ability to degrade organic contaminants and can stabilize heavy metals by acting as filters.
Plants primarily uptake contaminants through the root system, in which resides the principle mechanism of toxicity control. The enormous surface area is provided by the root system that helps in the absorption and accumulation of nutrients and water along with the non-essential toxic contaminants. Some plants can better remove contaminants as compared to others. Plants should therefore be suitably selected for the phytoremediation process so that they must be able to tolerate the various concentrations and types of pollutants present as well as withstand the climate of the area concerned. Another major concern is the depth of contamination. Grasses and ferns are used in the shallow contaminated region, whereas trees are used to remediate deeper contaminated and groundwater.
Phytoremediation therefore is an alternative technology that is applicable instead of conventional mechanical removal techniques that are energy and labour intensive and require huge capital inputs. It is an in situ technology for remediation utilizing the inherent potentiality of plants in environmental cleanup. It is an attractive, safe and low-risk method of remediation. Remediation with plants makes a site quite attractive. It is always advisable to use native plants as they are better adapted to the condition of the concerned region.
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The original post in this thread mentions one form of bioremediation called biostimulation “in which bacteria are motivated to start the process of bioremediation”. There are various examples in which the process of biostimulation can be used effectively to encourage the indigenous bacterial community to tackle environmental pollution. One recent study describes handling of the high concentrations of uranium (VI) generated from the mining of leachate in the Witwatersrand Basin, South Africa. In this study, tolerance of the indigenous bacterial species to high U(VI) concentrations along with the required amount of citric acid were optimised. Two bioreactor studies were performed. In the first, U(VI) was removed effectively from both low and high concentrations of U to below the levels set as safe for drinking water by South African National Standards. The second adapted to increasing U(VI) levels in feed water in the presence of sufficient electron donors. Relevant bacterial species such as Desulfovibrio and Geobacter were identified, which are known to reduce U(VI). Uranium was both precipitated intracellularly and as U(IV) oxides and TEM-EDS. The study confirmed the possibilities for optimising the tolerance of the indigenous bacteria for remediation of U(VI) and suggests that their system can be upscaled.

As previous posts have mentioned, it is important to be mindful of potential alterations in bacterial population diversity and abundance following bioremediation strategies including biostimulation. For example, one recent study examined consequences for bacterial abundance and diversity after biostimulation on anoxic marine sediments with high metal content. Molecular fingerprinting and next generation sequencing was used to characterise the bacterial population.  Adding organic (lactose and/or acetate) and/or inorganic compounds induced significant increases in bacterial growth but also changed bacterial diversity and assemblage composition. In experimental systems, supply of organic substrates only resulted in increases in the relative importance of sulphate reducing bacteria of the Desulfobacteraceae and Desulfobulbaceae families accompanied by a Flavobacteriaceae taxa. The opposite effect was achieved by when inorganic nutrients were also supplied. Increased bacterial metabolism along with the increase of bacterial taxa affiliated with Flavobacteriaceae resulted in a significant decrease of Cd and Zn associated with sedimentary organic matter and Pb and As associated with the residual fraction of the sediment. However, independent of the experimental conditions investigated, there was no dissolution of metals suggesting that bacterial assemblages were important in controlling metal solubilisation processes. The results of this study have thus clarified important biogeochemical interactions which influence metal behaviour and advance understanding of potential consequences of bio-treatments on fate of metals in contaminated marine sediments.

Maleke M, Williams P, Castillo J, Botes E, Ojo A, DeFlaun M, van Heerden E. Optimization of a bioremediation system of soluble uranium based on the biostimulation of an indigenous bacterial community. Environ Sci Pollut Res Int. 2014 Dec 30. [Epub ahead of print]

Fonti V, Beolchini F, Rocchetti L, Dell'Anno A. Bioremediation of contaminated marine sediments can enhance metal mobility due to changes of bacterial diversity. Water Res. 2014 doi: 10.1016/j.watres.2014.10.035. [Epub ahead of print]
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Do you have idea on difference between bioremediation and biodegradation with examples
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