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Bioremediation is a process used to treat contaminated media, including water, soil and subsurface material, by altering environmental conditions to stimulate growth of microorganisms and degrade the target pollutants. Cases where bioremediation is commonly seen is oil spills, soils contaminated with acidic mining drainage, underground pipe leaks, and crime scene cleanups.^[1] These toxic compounds are metabolized by enzymes present in microorganisms.^[2] Most bioremediation processes involve oxidation-reduction reactions where either an electron acceptor (commonly oxygen) is added to stimulate oxidation of a reduced pollutant (e.g. hydrocarbons) or an electron donor (commonly an organic substrate) is added to reduce oxidized pollutants (nitrate, perchlorate, oxidized metals, chlorinated solvents, explosives and propellants).^[3] Bioremediation is used to reduce the impact of byproducts created from anthropogenic activities, such as industrialization and agricultural processes.^[4] In many cases, bioremediation is less expensive and more sustainable than other remediation alternatives.^[5] Other remediation techniques include, thermal desorption, vitrification, air stripping, bioleaching, rhizofiltration, and soil washing. Biological treatment, bioremediation, is a similar approach used to treat wastes including wastewater, industrial waste and solid waste. The end goal of bioremediation is to remove or reduce harmful compounds to improve soil and water quality.^[2]

Contaminants can be removed or reduced with varying bioremediation techniques that are in-situ or ex-situ.^[6] Bioremediation techniques are classified based on the treatment locality.^[7] In-situ techniques treats polluted sites in a non-destructive manner and cost-effective. Whereas, ex-situ techniques commonly require the contaminated site to be excavated which increases costs.^[8] In both these approaches, additional nutrients, vitamins, minerals, and pH buffers may be added to optimize conditions for the microorganisms. In some cases, specialized microbial cultures are added (biostimulation) to further enhance biodegradation. Some examples of bioremediation related technologies are phytoremediation, bioventing, bioattenuation, biosparging, composting (biopiles and windrows), and landfarming.

Chemistry

Most bioremediation processes involve oxidation-reduction (Redox) reactions where a chemical species donates an electron (electron donor) to a different species that accepts the electron (electron acceptor). During this process, the electron donor is said to be oxidized while the electron acceptor is reduced. Common electron acceptors in bioremediation processes include oxygen, nitrate, manganese (III and IV), iron (III), sulfate, carbon dioxide and some pollutants (chlorinated solvents, explosives, oxidized metals, and radionuclides). Electron donors include sugars, fats, alcohols, natural organic material, fuel hydrocarbons and a variety of reduced organic pollutants. The redox potential for common biotransformation reactions is shown in the table.

Process	Reaction	Redox potential (E_h in mV)
aerobic	O₂ + 4e⁻ + 4H⁺ → 2H₂O	600 ~ 400
anaerobic
denitrification	2NO₃⁻ + 10e⁻ + 12H⁺ → N₂ + 6H₂O	500 ~ 200
manganese IV reduction	MnO₂ + 2e⁻ + 4H⁺ → Mn²⁺ + 2H₂O	400 ~ 200
iron III reduction	Fe(OH)₃ + e⁻ + 3H⁺ → Fe²⁺ + 3H₂O	300 ~ 100
sulfate reduction	SO₄²⁻ + 8e⁻ +10 H⁺ → H₂S + 4H₂O	0 ~ −150
fermentation	2CH₂O → CO₂ + CH₄	−150 ~ −220

Aerobic

In-situ techniques

Bioventing

link=|thumb Bioventing is a process that increases the oxygen or air flow into the unsaturated zone of the soil which increases the rate of natural in situ degradation of the targeted hydrocarbon contaminant.^[11] Bioventing, an aerobic bioremediation, is the most common form of oxidative bioremediation process where oxygen is provided as the electron acceptor for oxidation of petroleum, polyaromatic hydrocarbons (PAHs), phenols, and other reduced pollutants. Oxygen is generally the preferred electron acceptor because of the higher energy yield and because oxygen is required for some enzyme systems to initiate the degradation process.^[12] Microorganisms can degrade a wide variety of hydrocarbons, including components of gasoline, kerosene, diesel, and jet fuel. Under ideal aerobic conditions, the biodegradation rates of the low- to moderate-weight aliphatic, alicyclic, and aromatic compounds can be very high. As the molecular weight of the compound increases, so does the resistance to biodegradation.^[12] This results in higher contaminated volatile compounds, due to their high molecular weight, are more difficult to remove from the environment.

Most bioremediation processes involve oxidation-reduction reactions where either an electron acceptor (commonly oxygen) is added to stimulate oxidation of a reduced pollutant (e.g. hydrocarbons) or an electron donor (commonly an organic substrate) is added to reduce oxidized pollutants (nitrate, perchlorate, oxidized metals, chlorinated solvents, explosives and propellants).^[13] In both these approaches, additional nutrients, vitamins, minerals, and pH buffers may be added to optimize conditions for the microorganisms. In some cases, specialized microbial cultures are added (bioaugmentation) to further enhance biodegradation.

Common approaches for providing oxygen above the water table include landfarming, composting and bioventing. During landfarming, contaminated soils, sediments, or sludges are incorporated into the soil surface and periodically turned over (tilled) using conventional agricultural equipment to aerate the mixture. Composting accelerates pollutant biodegradation by mixing the waste to be treated with a bulking agent, forming into piles, and periodically mixed to increase oxygen transfer. Bioventing is a process that increases the oxygen or air flow into the unsaturated zone of the soil which increases the rate of natural in situ degradation of the targeted hydrocarbon contaminant.^[14]

Approaches for oxygen addition below the water table include recirculating aerated water through the treatment zone, addition of pure oxygen or peroxides, and air sparging. Recirculation systems typically consist of a combination of injection wells or galleries and one or more recovery wells where the extracted groundwater is treated, oxygenated, amended with nutrients and re-injected. However, the amount of oxygen that can be provided by this method is limited by the low solubility of oxygen in water (8 to 10 mg/L for water in equilibrium with air at typical temperatures). Greater amounts of oxygen can be provided by contacting the water with pure oxygen or addition of hydrogen peroxide (H₂O₂) to the water. In some cases, slurries of solid calcium or magnesium peroxide are injected under pressure through soil borings. These solid peroxides react with water releasing H₂O₂ which then decomposes releasing oxygen. Air sparging involves the injection of air under pressure below the water table. The air injection pressure must be great enough to overcome the hydrostatic pressure of the water and resistance to air flow through the soil.^[15]

Biostimulation

Bioremediation can be carried out by bacteria that is naturally present in the environment or adding nutrients, this process is called biostimulation.^[16]

Bacteria, also known as microbia, are naturally occurring in the environment and are used to degrade hydrocarbons.^[17] Many biological processes are sensitive to pH and function most efficiently in near neutral conditions. Low pH can interfere with pH homeostasis or increase the solubility of toxic metals. Microorganisms can expend cellular energy to maintain homeostasis or cytoplasmic conditions may change in response to external changes in pH. Anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis.^[18]

Bioremediation utilizing microbes works through the use of a microbial consortium. In this context, a microbial consortium is a symbiotically associated population of microbes that survive by utilizing the secondary metabolites of the species around them. An individual species of microbes is generally incapable of fully breaking down complex molecules, but may be able to partially degrade a compound. Another part of that partially digested molecule may be broken down by another species in the consortia, a pattern that can be repeated until the environmental contaminant is broken down into harmless byproducts.^[19]

In the event of biostimulation, adding nutrients that are limited to make the environment more suitable for bioremediation, nutrients such as nitrogen, phosphorus, oxygen, and carbon may be added to the system to improve effectiveness of the treatment.^[22] Nutrients are required for the biodegradation of oil pollution and can be used to reduce the negative output on the environment.^[23] Specific to marine oil spills, nitrogen and phosphorus have been key nutrients in biodegradation.^[24]

Many biological processes are sensitive to pH and function most efficiently in near neutral conditions. Low pH can interfere with pH homeostasis or increase the solubility of toxic metals. Microorganisms can expend cellular energy to maintain homeostasis or cytoplasmic conditions may change in response to external changes in pH. Some anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis.^[25]

Anaerobic bioremediation can be employed to treat a broad range of oxidized contaminants including chlorinated ethenes (PCE, TCE, DCE, VC), chlorinated ethanes (TCA, DCA), chloromethanes (CT, CF), chlorinated cyclic hydrocarbons, various energetics (e.g., perchlorate,^[26] RDX, TNT), and nitrate.^[10] This process involves the addition of an electron donor to: 1) deplete background electron acceptors including oxygen, nitrate, oxidized iron and manganese and sulfate; and 2) stimulate the biological and/or chemical reduction of the oxidized pollutants. Hexavalent chromium (Cr[VI]) and uranium (U[VI]) can be reduced to less mobile and/or less toxic forms (e.g., Cr[III], U[IV]). Similarly, reduction of sulfate to sulfide (sulfidogenesis) can be used to precipitate certain metals (e.g., zinc, cadmium). The choice of substrate and the method of injection depend on the contaminant type and distribution in the aquifer, hydrogeology, and remediation objectives. Substrate can be added using conventional well installations, by direct-push technology, or by excavation and backfill such as permeable reactive barriers (PRB) or biowalls. Slow-release products composed of edible oils or solid substrates tend to stay in place for an extended treatment period. Soluble substrates or soluble fermentation products of slow-release substrates can potentially migrate via advection and diffusion, providing broader but shorter-lived treatment zones. The added organic substrates are first fermented to hydrogen (H₂) and volatile fatty acids (VFAs). The VFAs, including acetate, lactate, propionate and butyrate, provide carbon and energy for bacterial metabolism.^[10]^[13]

Bioattenuation

During bioattenuation, biodegradation occurs naturally with the addition of nutrients or bacteria. The indigenous microbes present will determine the metabolic activity and act as a natural attenuation.^[27] While there is no anthropogenic involvement in bioattenuation, the contaminated site must still be monitored.^[27]

Biosparging

Biosparging is the process of groundwater remediation as oxygen, and possible nutrients, is injected. When oxygen is injected, indigenous bacteria are stimulated to increase rate of degradation.^[28] However, biosparging focuses on saturated contaminated zones, specifically related to ground water remediation.^[29]

Ex-situ techniques

Biopiles

Biopiles, similar to bioventing, are used to reduce petroleum pollutants by introducing aerobic hydrocarbons to contaminated soils. However, the soil is excavated and piled with an aeration system. This aeration system enhances microbial activity by introducing oxygen under positive pressure or removes oxygen under negative pressure.^[30]

Windrows

Windrow systems are similar to compost techniques where soil is periodically turned in order to enhance aeration.^[33] This periodic turning also allows contaminants present in the soil to be uniformly distributed which accelerates the process of bioremediation.^[34]

Landfarming

Landfarming, or land treatment, is a method commonly used for sludge spills. This method disperses contaminated soil and aerates the soil by cyclically rotating.^[35] This process is an above land application and contaminated soils are required to be shallow in order for microbial activity to be stimulated. However, if the contamination is deeper than 5 feet, then the soil is required to be excavated to above ground.^[36]

Heavy metals

Heavy metals become present in the environment due to anthropogenic activities or natural factors.^[37] Anthropogenic activities include industrial emissions, electronic waste, and ore mining. Natural factors include mineral weathering, soil erosion and forest fires.^[38] Heavy metals including cadmium, chromium, lead and uranium are unlike organic compounds and cannot be biodegraded. However, bioremediation processes can potentially be used to reduce the mobility of these material in the subsurface, reducing the potential for human and environmental exposure.^[39] Heavy metals from these factors are predominantly present in water sources due to runoff where it is uptake by marine fauna and flora.^[38]

The mobility of certain metals including chromium (Cr) and uranium (U) varies depending on the oxidation state of the material.^[40] Microorganisms can be used to reduce the toxicity and mobility of chromium by reducing hexavalent chromium, Cr(VI) to trivalent Cr (III).^[41] Uranium can be reduced from the more mobile U(VI) oxidation state to the less mobile U(IV) oxidation state.^[42]^[43] Microorganisms are used in this process because the reduction rate of these metals is often slow unless catalyzed by microbial interactions^[44] Research is also underway to develop methods to remove metals from water by enhancing the sorption of the metal to cell walls.^[44] This approach has been evaluated for treatment of cadmium,^[45] chromium,^[46] and lead.^[47] Phytoextraction processes concentrate contaminants in the biomass for subsequent removal.

Limitations of bioremediation

Bioremediation can be used to completely mineralize organic pollutants, to partially transform the pollutants, or alter their mobility. Heavy metals and radionuclides are elements that cannot be biodegraded, but can be bio-transformed to less mobile forms.^[48]^[49]^[50] In some cases, microbes do not fully mineralize the pollutant, potentially producing a more toxic compound.^[50] For example, under anaerobic conditions, the reductive dehalogenation of TCE may produce dichloroethylene (DCE) and vinyl chloride (VC), which are suspected or known carcinogens.^[48] However, the microorganism Dehalococcoides can further reduce DCE and VC to the non-toxic product ethene.^[51] Additional research is required to develop methods to ensure that the products from biodegradation are less persistent and less toxic than the original contaminant.^[50] Thus, the metabolic and chemical pathways of the microorganisms of interest must be known.^[48] In addition, knowing these pathways will help develop new technologies that can deal with sites that have uneven distributions of a mixture of contaminants.^[52]

Also, for biodegradation to occur, there must be a microbial population with the metabolic capacity to degrade the pollutant, an environment with the right growing conditions for the microbes, and the right amount of nutrients and contaminants.^[52]^[49] The biological processes used by these microbes are highly specific, therefore, many environmental factors must be taken into account and regulated as well.^[52]^[48] Thus, bioremediation processes must be specifically made in accordance to the conditions at the contaminated site.^[48] Also, because many factors are interdependent, small-scale tests are usually performed before carrying out the procedure at the contaminated site.^[49] However, it can be difficult to extrapolate the results from the small-scale test studies into big field operations.^[52] In many cases, bioremediation takes more time than other alternatives such as land filling and incineration.^[52]^[48] Another example is bioventing, this method is inexpensive to bioremediate contaminated sites, however this process is extensive and can take a few years to decontaminate a site.^[53]

In agricultural industries, the use of pesticides is a top factor in direct soil contamination and runoff water contamination. The limitation or remediation of pesticides is the low bioavailability.^[54] Altering the pH and temperature of the contaminated soil is a resolution to increase bioavailability which, in turn, increased degradation of harmful compounds.^[54] The compoundacrylonitrile is commonly produced in industrial setting but adversely contaminates soils. Microorganisms containing nitrile hydratases (NHase) degraded harmful acrylonitrile compounds into non-polluting substances.^[55]

Since the experience with harmful contaminants are limited, laboratory practices are required to evaluate effectiveness, treatment designs, and estimate treatment times.^[56] Bioremediation processes may take several months to several years depending on the size of the contaminated area.^[57]

Genetic engineering

The use of genetic engineering to create organisms specifically designed for bioremediation is under preliminary research.^[58] Two category of genes can be inserted in the organism: degradative genes which encode proteins required for the degradation of pollutants, and reporter genes that are able to monitor pollution levels.^[59] Numerous members of Pseudomonas have also been modified with the lux gene, but for the detection of the polyaromatic hydrocarbon naphthalene. A field test for the release of the modified organism has been successful on a moderately large scale.^[60]

There are concerns surrounding release and containment of genetically modified organisms into the environment due to the potential of horizontal gene transfer.^[61] Genetically modified organisms are classified and controlled under the Toxic Substances Control Act of 1976 under United States Environmental Protection Agency.^[62] Measures have been created to address these concerns. Organisms can be modified such that they can only survive and grow under specific sets of environmental conditions.^[61] In addition, the tracking of modified organisms can be made easier with the insertion of bioluminescence genes for visual identification.^[63]

Genetically modified organisms have been created to treat oil spills and break down certain plastics (PET)^[64]

References

^ Reavill, Gil (2007). "Aftermath, INC: Cleaning up after CSI goes home". Gotham books. 6: 284. ISSN 2007-2013. {{cite journal}}: Check |issn= value (help)
^ ^a ^b ^c Canak, Stevan; Berezljev, Ljiljana; Borojevic, Krstan; Asotic, Jasminka; Ketin, Sonja (2019). "Bioremediation and "green chemistry"". Fresenius Environmental Bulletin. 28 (4): 3056–3064.
^ Introduction to In Situ Bioremediation of Groundwater (PDF). US Environmental Protection Agency. 2013. p. 30.
^ Singh, Nitika; Kumar, Abhishek; Sharma, Bechan (2019), Role of Fungal Enzymes for Bioremediation of Hazardous Chemicals, Fungal Biology, vol. 3, Cham: Springer International Publishing, pp. 237–256, doi:10.1007/978-3-030-25506-0_9, ISBN 978-3-030-25506-0
^ "Green Remediation Best Management Practices: Sites with Leaking Underground Storage Tank Systems. EPA 542-F-11-008" (PDF). EPA. June 2011.
^ Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.
^ Sharma, Jot (2019). "Advantages and Limitations of In Situ Methods of Bioremediation". Recent Adv Biol Med. 5 (2019): 10941. doi:10.18639/RABM.2019.955923.
^ Kensa, V. Mary (2011). "BIOREMEDIATION - AN OVERVIEW". I Control Pollution. 27 (2): 161–168. ISSN 0970-2083.
^ Jørgensen, Kirsten S. (2007), "In Situ Bioremediation", Advances in Applied Microbiology, vol. 61, Academic Press, pp. 285–305, doi:10.1016/S0065-2164(06)61008-3
^ ^a ^b ^c Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.
^ Frutos, F. Javier García; Escolano, Olga; García, Susana; Babín, Mar; Fernández, M. Dolores (2010). "Bioventing remediation and ecotoxicity evaluation of phenanthrene-contaminated soil". Journal of Hazardous Materials. 183 (1–3): 806–813. doi:10.1016/j.jhazmat.2010.07.098. ISSN 0304-3894.
^ ^a ^b Norris, Robert (1993). Handbook of Bioremediation. CRC Press. p. 45. ISBN 9781351363457.
^ ^a ^b Introduction to In Situ Bioremediation of Groundwater (PDF). US Environmental Protection Agency. 2013. p. 30.
^ Frutos, F. Javier García; Escolano, Olga; García, Susana; Babín, Mar; Fernández, M. Dolores (November 2010). "Bioventing remediation and ecotoxicity evaluation of phenanthrene-contaminated soil". Journal of Hazardous Materials. 183 (1–3): 806–813. doi:10.1016/j.jhazmat.2010.07.098. ISSN 0304-3894. PMID 20800967.
^ Leeson, Andrea (2002). Air Sparging Design Paradigm. http://www.dtic.mil/get-tr-doc/pdf?AD=ADA492279: BATTELLE COLUMBUS OH. {{cite book}}: External link in |location= (help)CS1 maint: location (link)
^ Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.
^ Lee, Dong Wan; Lee, Hanbyul; Lee, Aslan Hwanhwi; Kwon, Bong-Oh; Khim, Jong Seong; Yim, Un Hyuk; Kim, Beom Seok; Kim, Jae-Jin (2018). "Microbial community composition and PAHs removal potential of indigenous bacteria in oil contaminated sediment of Taean coast, Korea". Environmental Pollution. 234: 503–512. doi:10.1016/j.envpol.2017.11.097. ISSN 0269-7491.
^ Slonczewski, J.L. (2009). "Stress Responses: pH". In Schaechter, Moselio (ed.). Encyclopedia of microbiology (3rd ed.). Elsevier. pp. 477–484. doi:10.1016/B978-012373944-5.00100-0. ISBN 978-0-12-373944-5.
^ Paniagua-Michel, J.; Fathepure, Babu Z. (2018), Kumar, Vivek; Kumar, Manoj; Prasad, Ram (eds.), "Microbial Consortia and Biodegradation of Petroleum Hydrocarbons in Marine Environments", Microbial Action on Hydrocarbons, Singapore: Springer Singapore, pp. 1–20, doi:10.1007/978-981-13-1840-5_1, ISBN 978-981-13-1839-9, retrieved 2021-03-03
^ Mora, Rebecca H.; Macbeth, Tamzen W.; MacHarg, Tara; Gundarlahalli, Jagadish; Holbrook, Holly; Schiff, Paul (2008). "Enhanced bioremediation using whey powder for a trichloroethene plume in a high-sulfate, fractured granitic aquifer". Remediation Journal. 18 (3): 7–30. doi:10.1002/rem.20168. ISSN 1520-6831.
^ Mora, Rebecca H.; Macbeth, Tamzen W.; MacHarg, Tara; Gundarlahalli, Jagadish; Holbrook, Holly; Schiff, Paul (2008). "Enhanced bioremediation using whey powder for a trichloroethene plume in a high-sulfate, fractured granitic aquifer". Remediation Journal. 18 (3): 7–30. doi:10.1002/rem.20168. ISSN 1520-6831.
^ Adams, Omokhagbor (February 28, 2015). "Bioremediation, Biostimulation and Bioaugmentation: A Review". International Journal of Environmental Bioremediation and Biodegredation. 3 (1): 28–39 – via Research Gate.
^ Chen, Qingguo; Bao, Bo; Li, Yijing; Liu, Mei; Zhu, Baikang; Mu, Jun; Chen, Zhi (2020). "Effects of marine oil pollution on microbial diversity in coastal waters and stimulating indigenous microorganism bioremediation with nutrients". Regional Studies in Marine Science. 39: 101395. doi:10.1016/j.rsma.2020.101395. ISSN 2352-4855.
^ Varjani, Sunita J.; Upasani, Vivek N. (2017). "A new look on factors affecting microbial degradation of petroleum hydrocarbon pollutants". International Biodeterioration & Biodegradation. 120: 71–83. doi:10.1016/j.ibiod.2017.02.006. ISSN 0964-8305.
^ Slonczewski, J.L. (2009). "Stress Responses: pH". In Schaechter, Moselio (ed.). Encyclopedia of microbiology (3rd ed.). Elsevier. pp. 477–484. doi:10.1016/B978-012373944-5.00100-0. ISBN 978-0-12-373944-5.
^ Coates J, Jackson W (2008). "Principles of perchlorate treatment". In Stroo H, Ward CH (eds.). In situ bioremediation of perchlorate in groundwater. New York: Springer. pp. 29–53. doi:10.1007/978-0-387-84921-8_3. ISBN 978-0-387-84921-8.
^ ^a ^b Ying, Guang-Guo (2018), "Chapter 14 - Remediation and Mitigation Strategies", Integrated Analytical Approaches for Pesticide Management, Academic Press, pp. 207–217, doi:10.1016/b978-0-12-816155-5.00014-2, ISBN 978-0-12-816155-5
^ Vidali, M (2001). "Bioremediation. An overview*". Pure and Applied Chemistry. 73 (7): 1163–1172.
^ Johnson, Paul C.; Johnson, Richard L.; Bruce, Cristin L.; Leeson, Andrea (2001). "Advances in In Situ Air Sparging/Biosparging". Bioremediation Journal. 5 (4): 251–266. doi:10.1080/20018891079311. ISSN 1088-9868.
^ Emami, Somayeh; Pourbabaee, Ahmad Ali; Alikhani, Hossein Ali (2012). "Bioremediation Principles and Techniques on Petroleum Hydrocarbon Contaminated Soil". Technical Journal of Engineering and Applied Sciences. 2 (10): 320–323. ISSN 2051-0853.
^ Waters, J.M; Lambert, C; Reid, D; Shaw, R (2002). Redevelopment of the former Shell Haven refinery. Southampton, UK: WIT Press. pp. 77–85. ISBN 1-85312-918-6.
^ Waters, J.M; Lambert, C; Reid, D; Shaw, R (2002). Redevelopment of the former Shell Haven refinery. Southampton, UK: WIT Press. pp. 77–85. ISBN 1-85312-918-6.
^ Rakshit, Amitava; Parihar, Manoj; Sarkar, Binoy; Singh, Harikesh B.; Fraceto, Leonardo Fernandes (2021). Bioremediation Science: From Theory to Practice. CRC Press. ISBN 978-1-000-28046-3.
^ Azubuike, Christopher Chibueze; Chikere, Chioma Blaise; Okpokwasili, Gideon Chijioke (2016). "Bioremediation techniques–classification based on site of application: principles, advantages, limitations and prospects". World Journal of Microbiology and Biotechnology. 32 (11): 180. doi:10.1007/s11274-016-2137-x. ISSN 1573-0972. PMC 5026719. PMID 27638318.{{cite journal}}: CS1 maint: PMC format (link)
^ Kumar, Vineet; Shahi, S. K.; Singh, Simranjeet (2018), "Bioremediation: An Eco-sustainable Approach for Restoration of Contaminated Sites", Microbial Bioprospecting for Sustainable Development, Singapore: Springer, pp. 115–136, doi:10.1007/978-981-13-0053-0_6, ISBN 978-981-13-0053-0
^ United States Environmental Protection Agency (USEPA) (2017) How To Evaluate Alternative Cleanup Technologies For Underground Storage Tank Sites. A Guide For Corrective Action Plan Reviewers. EPA 510-B-17-003. https://www.epa.gov/sites/production/files/2014-03/documents/tum_ch5.pdf
^ Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.
^ ^a ^b Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.
^ Ghosh, M; Singh, S.P (2005). "A Review on Phytoremediation of Heavy Metals and Utilization of It's by Products" (PDF). Asian Journal on Energy and Environment. 6 (4): 214–231.
^ R.G. Ford, R.T. Wilkin, and R.W. Puls (2007). Monitored natural attenuation of inorganic contaminants in groundwater, Volume 1 Technical basis for assessment (PDF). U.S. Environmental Protection Agency, EPA/600/R-07/139. OCLC 191800707.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ R.G. Ford, R.T. Wilkin, and R.W. Puls (2007). Monitored Natural Attenuation of Inorganic Contaminants in Groundwater, Volume 2 - Assessment for Non-Radionulcides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium (PDF). USEPA.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ Williams KH, Bargar JR, Lloyd JR, Lovley DR (June 2013). "Bioremediation of uranium-contaminated groundwater: a systems approach to subsurface biogeochemistry". Current Opinion in Biotechnology. 24 (3): 489–97. doi:10.1016/j.copbio.2012.10.008. PMID 23159488.
^ R.G. Ford and R.T. Wilkin (2007). Monitored natural attenuation of inorganic contaminants in groundwater, Volume 3 Assessment for Radionuclides Including Tritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium (PDF). U.S. Environmental Protection Agency, EPA/600/R-10/093.
^ ^a ^b Anna., Hazen, Terry. Palmisano (2003). Bioremediation of Metals and Radionuclides : What It Is and How It Works (2nd Edition). Lawrence Berkeley National Laboratory. OCLC 316485842.{{cite book}}: CS1 maint: multiple names: authors list (link)
^ Ansari MI, Malik A (November 2007). "Biosorption of nickel and cadmium by metal resistant bacterial isolates from agricultural soil irrigated with industrial wastewater". Bioresource Technology. 98 (16): 3149–53. doi:10.1016/j.biortech.2006.10.008. PMID 17166714.
^ Durán U, Coronado-Apodaca KG, Meza-Escalante ER, Ulloa-Mercado G, Serrano D (May 2018). "Two combined mechanisms responsible to hexavalent chromium removal on active anaerobic granular consortium". Chemosphere. 198: 191–197. Bibcode:2018Chmsp.198..191D. doi:10.1016/j.chemosphere.2018.01.024. PMID 29421729.
^ Tripathi M, Munot HP, Shouche Y, Meyer JM, Goel R (May 2005). "Isolation and functional characterization of siderophore-producing lead- and cadmium-resistant Pseudomonas putida KNP9". Current Microbiology. 50 (5): 233–7. doi:10.1007/s00284-004-4459-4. PMID 15886913. S2CID 21061197.
^ ^a ^b ^c ^d ^e ^f Juwarkar AA, Singh SK, Mudhoo A (2010). "A comprehensive overview of elements in bioremediation". Reviews in Environmental Science and Bio/Technology. 9 (3): 215–88. doi:10.1007/s11157-010-9215-6. S2CID 85268562.
^ ^a ^b ^c Boopathy, R (2000). "Factors limiting bioremediation technologies". Bioresource Technology. 74: 63–7. doi:10.1016/S0960-8524(99)00144-3.
^ ^a ^b ^c Wexler, editor-in-chief, Philip (2014). Encyclopedia of toxicology (3rd ed.). San Diego, Ca: Academic Press Inc. p. 489. ISBN 9780123864543. {{cite book}}: |first1= has generic name (help)CS1 maint: multiple names: authors list (link)
^ Maymó-Gatell, Xavier; Chien, Yueh-tyng; Gossett, James M.; Zinder, Stephen H. (1997-06-06). "Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene". Science. 276 (5318): 1568–1571. doi:10.1126/science.276.5318.1568. ISSN 0036-8075. PMID 9171062.
^ ^a ^b ^c ^d ^e Vidali, M. (2001). "Bioremediation. An overview" (PDF). Pure and Applied Chemistry. 73 (7): 1163–72. doi:10.1351/pac200173071163. S2CID 18507182.
^ Sharma, Jot (2019). "Advantages and Limitations of In Situ Methods of Bioremediation". Recent Adv Biol Med. 5 (2019): 10941. doi:10.18639/RABM.2019.955923.
^ ^a ^b Odukkathil, Greeshma; Vasudevan, Namasivayam (2013). "Toxicity and bioremediation of pesticides in agricultural soil". Reviews in Environmental Science and Bio/Technology. 12 (4): 421–444. doi:10.1007/s11157-013-9320-4. ISSN 1569-1705.
^ Supreetha, K.; Rao, Saroja Narsing; Srividya, D.; Anil, H. S.; Kiran, S. (2019). "Advances in cloning, structural and bioremediation aspects of nitrile hydratases". Molecular Biology Reports. 46 (4): 4661–4673. doi:10.1007/s11033-019-04811-w. ISSN 1573-4978.
^ Sharma, Jot (2019). "Advantages and Limitations of In Situ Methods of Bioremediation". Recent Adv Biol Med. 5 (2019): 10941. doi:10.18639/RABM.2019.955923.
^ National Service Center for Environmental Publications (2012) A Citizen's Guide to Bioremediation. https://www.epa.gov/remedytech/citizens-guide-bioremediation#:~:text=The%20Citizen's%20Guide%20series%20is,up%20contaminated%20soil%20and%20groundwater.
^ Lovley DR (October 2003). "Cleaning up with genomics: applying molecular biology to bioremediation". Nature Reviews. Microbiology. 1 (1): 35–44. doi:10.1038/nrmicro731. PMID 15040178. S2CID 40604152.
^ Menn FM, Easter JP, Sayler GS (2001). "Genetically Engineered Microorganisms and Bioremediation". Biotechnology Set. pp. 441–63. doi:10.1002/9783527620999.ch21m. ISBN 978-3-527-62099-9.
^ Ripp S, Nivens DE, Ahn Y, Werner C, Jarrell J, Easter JP, Cox CD, Burlage RS, Sayler GS (2000). "Controlled Field Release of a Bioluminescent Genetically Engineered Microorganism for Bioremediation Process Monitoring and Control". Environmental Science & Technology. 34 (5): 846–53. Bibcode:2000EnST...34..846R. doi:10.1021/es9908319.
^ ^a ^b Davison J (December 2005). "Risk mitigation of genetically modified bacteria and plants designed for bioremediation". Journal of Industrial Microbiology & Biotechnology. 32 (11–12): 639–50. doi:10.1007/s10295-005-0242-1. PMID 15973534. S2CID 7986980.
^ Sayler GS, Ripp S (June 2000). "Field applications of genetically engineered microorganisms for bioremediation processes". Current Opinion in Biotechnology. 11 (3): 286–9. doi:10.1016/S0958-1669(00)00097-5. PMID 10851144.
^ Shanker R, Purohit HJ, Khanna P (1998). "Bioremediation for Hazardous Waste Management: The Indian Scenario". In Irvine RL, Sikdar SK (eds.). Bioremediation Technologies: Principles and Practice. pp. 81–96. ISBN 978-1-56676-561-9.
^ Building a circular economy with synthetic biology

External links

[1] Reavill, Gil (2007). "Aftermath, INC: Cleaning up after CSI goes home". Gotham books. 6: 284. ISSN 2007-2013. {{cite journal}}: Check |issn= value (help)

[:02-2] Canak, Stevan; Berezljev, Ljiljana; Borojevic, Krstan; Asotic, Jasminka; Ketin, Sonja (2019). "Bioremediation and "green chemistry"". Fresenius Environmental Bulletin. 28 (4): 3056–3064.

[:22-3] Introduction to In Situ Bioremediation of Groundwater (PDF). US Environmental Protection Agency. 2013. p. 30.

[4] Singh, Nitika; Kumar, Abhishek; Sharma, Bechan (2019), Role of Fungal Enzymes for Bioremediation of Hazardous Chemicals, Fungal Biology, vol. 3, Cham: Springer International Publishing, pp. 237–256, doi:10.1007/978-3-030-25506-0_9, ISBN 978-3-030-25506-0

[5] "Green Remediation Best Management Practices: Sites with Leaking Underground Storage Tank Systems. EPA 542-F-11-008" (PDF). EPA. June 2011.

[:42-6] Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.

[:7-7] Sharma, Jot (2019). "Advantages and Limitations of In Situ Methods of Bioremediation". Recent Adv Biol Med. 5 (2019): 10941. doi:10.18639/RABM.2019.955923.

[8] Kensa, V. Mary (2011). "BIOREMEDIATION - AN OVERVIEW". I Control Pollution. 27 (2): 161–168. ISSN 0970-2083.

[9] Jørgensen, Kirsten S. (2007), "In Situ Bioremediation", Advances in Applied Microbiology, vol. 61, Academic Press, pp. 285–305, doi:10.1016/S0065-2164(06)61008-3

[:4-10] Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.

[11] Frutos, F. Javier García; Escolano, Olga; García, Susana; Babín, Mar; Fernández, M. Dolores (2010). "Bioventing remediation and ecotoxicity evaluation of phenanthrene-contaminated soil". Journal of Hazardous Materials. 183 (1–3): 806–813. doi:10.1016/j.jhazmat.2010.07.098. ISSN 0304-3894.

[:32-12] Norris, Robert (1993). Handbook of Bioremediation. CRC Press. p. 45. ISBN 9781351363457.

[:2-13] Introduction to In Situ Bioremediation of Groundwater (PDF). US Environmental Protection Agency. 2013. p. 30.

[14] Frutos, F. Javier García; Escolano, Olga; García, Susana; Babín, Mar; Fernández, M. Dolores (November 2010). "Bioventing remediation and ecotoxicity evaluation of phenanthrene-contaminated soil". Journal of Hazardous Materials. 183 (1–3): 806–813. doi:10.1016/j.jhazmat.2010.07.098. ISSN 0304-3894. PMID 20800967.

[15] Leeson, Andrea (2002). Air Sparging Design Paradigm. http://www.dtic.mil/get-tr-doc/pdf?AD=ADA492279: BATTELLE COLUMBUS OH. {{cite book}}: External link in |location= (help)CS1 maint: location (link)

[:43-16] Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.

[17] Lee, Dong Wan; Lee, Hanbyul; Lee, Aslan Hwanhwi; Kwon, Bong-Oh; Khim, Jong Seong; Yim, Un Hyuk; Kim, Beom Seok; Kim, Jae-Jin (2018). "Microbial community composition and PAHs removal potential of indigenous bacteria in oil contaminated sediment of Taean coast, Korea". Environmental Pollution. 234: 503–512. doi:10.1016/j.envpol.2017.11.097. ISSN 0269-7491.

[18] Slonczewski, J.L. (2009). "Stress Responses: pH". In Schaechter, Moselio (ed.). Encyclopedia of microbiology (3rd ed.). Elsevier. pp. 477–484. doi:10.1016/B978-012373944-5.00100-0. ISBN 978-0-12-373944-5.

[19] Paniagua-Michel, J.; Fathepure, Babu Z. (2018), Kumar, Vivek; Kumar, Manoj; Prasad, Ram (eds.), "Microbial Consortia and Biodegradation of Petroleum Hydrocarbons in Marine Environments", Microbial Action on Hydrocarbons, Singapore: Springer Singapore, pp. 1–20, doi:10.1007/978-981-13-1840-5_1, ISBN 978-981-13-1839-9, retrieved 2021-03-03

[20] Mora, Rebecca H.; Macbeth, Tamzen W.; MacHarg, Tara; Gundarlahalli, Jagadish; Holbrook, Holly; Schiff, Paul (2008). "Enhanced bioremediation using whey powder for a trichloroethene plume in a high-sulfate, fractured granitic aquifer". Remediation Journal. 18 (3): 7–30. doi:10.1002/rem.20168. ISSN 1520-6831.

[21] Mora, Rebecca H.; Macbeth, Tamzen W.; MacHarg, Tara; Gundarlahalli, Jagadish; Holbrook, Holly; Schiff, Paul (2008). "Enhanced bioremediation using whey powder for a trichloroethene plume in a high-sulfate, fractured granitic aquifer". Remediation Journal. 18 (3): 7–30. doi:10.1002/rem.20168. ISSN 1520-6831.

[22] Adams, Omokhagbor (February 28, 2015). "Bioremediation, Biostimulation and Bioaugmentation: A Review". International Journal of Environmental Bioremediation and Biodegredation. 3 (1): 28–39 – via Research Gate.

[23] Chen, Qingguo; Bao, Bo; Li, Yijing; Liu, Mei; Zhu, Baikang; Mu, Jun; Chen, Zhi (2020). "Effects of marine oil pollution on microbial diversity in coastal waters and stimulating indigenous microorganism bioremediation with nutrients". Regional Studies in Marine Science. 39: 101395. doi:10.1016/j.rsma.2020.101395. ISSN 2352-4855.

[24] Varjani, Sunita J.; Upasani, Vivek N. (2017). "A new look on factors affecting microbial degradation of petroleum hydrocarbon pollutants". International Biodeterioration & Biodegradation. 120: 71–83. doi:10.1016/j.ibiod.2017.02.006. ISSN 0964-8305.

[25] Slonczewski, J.L. (2009). "Stress Responses: pH". In Schaechter, Moselio (ed.). Encyclopedia of microbiology (3rd ed.). Elsevier. pp. 477–484. doi:10.1016/B978-012373944-5.00100-0. ISBN 978-0-12-373944-5.

[26] Coates J, Jackson W (2008). "Principles of perchlorate treatment". In Stroo H, Ward CH (eds.). In situ bioremediation of perchlorate in groundwater. New York: Springer. pp. 29–53. doi:10.1007/978-0-387-84921-8_3. ISBN 978-0-387-84921-8.

[:5-27] Ying, Guang-Guo (2018), "Chapter 14 - Remediation and Mitigation Strategies", Integrated Analytical Approaches for Pesticide Management, Academic Press, pp. 207–217, doi:10.1016/b978-0-12-816155-5.00014-2, ISBN 978-0-12-816155-5

[28] Vidali, M (2001). "Bioremediation. An overview*". Pure and Applied Chemistry. 73 (7): 1163–1172.

[29] Johnson, Paul C.; Johnson, Richard L.; Bruce, Cristin L.; Leeson, Andrea (2001). "Advances in In Situ Air Sparging/Biosparging". Bioremediation Journal. 5 (4): 251–266. doi:10.1080/20018891079311. ISSN 1088-9868.

[30] Emami, Somayeh; Pourbabaee, Ahmad Ali; Alikhani, Hossein Ali (2012). "Bioremediation Principles and Techniques on Petroleum Hydrocarbon Contaminated Soil". Technical Journal of Engineering and Applied Sciences. 2 (10): 320–323. ISSN 2051-0853.

[31] Waters, J.M; Lambert, C; Reid, D; Shaw, R (2002). Redevelopment of the former Shell Haven refinery. Southampton, UK: WIT Press. pp. 77–85. ISBN 1-85312-918-6.

[32] Waters, J.M; Lambert, C; Reid, D; Shaw, R (2002). Redevelopment of the former Shell Haven refinery. Southampton, UK: WIT Press. pp. 77–85. ISBN 1-85312-918-6.

[33] Rakshit, Amitava; Parihar, Manoj; Sarkar, Binoy; Singh, Harikesh B.; Fraceto, Leonardo Fernandes (2021). Bioremediation Science: From Theory to Practice. CRC Press. ISBN 978-1-000-28046-3.

[34] Azubuike, Christopher Chibueze; Chikere, Chioma Blaise; Okpokwasili, Gideon Chijioke (2016). "Bioremediation techniques–classification based on site of application: principles, advantages, limitations and prospects". World Journal of Microbiology and Biotechnology. 32 (11): 180. doi:10.1007/s11274-016-2137-x. ISSN 1573-0972. PMC 5026719. PMID 27638318.{{cite journal}}: CS1 maint: PMC format (link)

[35] Kumar, Vineet; Shahi, S. K.; Singh, Simranjeet (2018), "Bioremediation: An Eco-sustainable Approach for Restoration of Contaminated Sites", Microbial Bioprospecting for Sustainable Development, Singapore: Springer, pp. 115–136, doi:10.1007/978-981-13-0053-0_6, ISBN 978-981-13-0053-0

[36] United States Environmental Protection Agency (USEPA) (2017) How To Evaluate Alternative Cleanup Technologies For Underground Storage Tank Sites. A Guide For Corrective Action Plan Reviewers. EPA 510-B-17-003. https://www.epa.gov/sites/production/files/2014-03/documents/tum_ch5.pdf

[:44-37] Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.

[:6-38] Kapahi, Meena; Sachdeva, Sarita (2019). "Bioremediation Options for Heavy Metal Pollution". Journal of Health & Pollution. 9 (24). doi:10.5696/2156-9614-9.24.191203. ISSN 2156-9614. PMC 6905138. PMID 31893164.

[39] Ghosh, M; Singh, S.P (2005). "A Review on Phytoremediation of Heavy Metals and Utilization of It's by Products" (PDF). Asian Journal on Energy and Environment. 6 (4): 214–231.

[40] R.G. Ford, R.T. Wilkin, and R.W. Puls (2007). Monitored natural attenuation of inorganic contaminants in groundwater, Volume 1 Technical basis for assessment (PDF). U.S. Environmental Protection Agency, EPA/600/R-07/139. OCLC 191800707.{{cite book}}: CS1 maint: multiple names: authors list (link)

[41] R.G. Ford, R.T. Wilkin, and R.W. Puls (2007). Monitored Natural Attenuation of Inorganic Contaminants in Groundwater, Volume 2 - Assessment for Non-Radionulcides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium (PDF). USEPA.{{cite book}}: CS1 maint: multiple names: authors list (link)

[42] Williams KH, Bargar JR, Lloyd JR, Lovley DR (June 2013). "Bioremediation of uranium-contaminated groundwater: a systems approach to subsurface biogeochemistry". Current Opinion in Biotechnology. 24 (3): 489–97. doi:10.1016/j.copbio.2012.10.008. PMID 23159488.

[43] R.G. Ford and R.T. Wilkin (2007). Monitored natural attenuation of inorganic contaminants in groundwater, Volume 3 Assessment for Radionuclides Including Tritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium (PDF). U.S. Environmental Protection Agency, EPA/600/R-10/093.

[:0-44] Anna., Hazen, Terry. Palmisano (2003). Bioremediation of Metals and Radionuclides : What It Is and How It Works (2nd Edition). Lawrence Berkeley National Laboratory. OCLC 316485842.{{cite book}}: CS1 maint: multiple names: authors list (link)

[source_3-45] Ansari MI, Malik A (November 2007). "Biosorption of nickel and cadmium by metal resistant bacterial isolates from agricultural soil irrigated with industrial wastewater". Bioresource Technology. 98 (16): 3149–53. doi:10.1016/j.biortech.2006.10.008. PMID 17166714.

[:1-46] Durán U, Coronado-Apodaca KG, Meza-Escalante ER, Ulloa-Mercado G, Serrano D (May 2018). "Two combined mechanisms responsible to hexavalent chromium removal on active anaerobic granular consortium". Chemosphere. 198: 191–197. Bibcode:2018Chmsp.198..191D. doi:10.1016/j.chemosphere.2018.01.024. PMID 29421729.

[source_1-47] Tripathi M, Munot HP, Shouche Y, Meyer JM, Goel R (May 2005). "Isolation and functional characterization of siderophore-producing lead- and cadmium-resistant Pseudomonas putida KNP9". Current Microbiology. 50 (5): 233–7. doi:10.1007/s00284-004-4459-4. PMID 15886913. S2CID 21061197.

[Disadv-Comprehensive-48] ^ ^a ^b ^c ^d ^e ^f Juwarkar AA, Singh SK, Mudhoo A (2010). "A comprehensive overview of elements in bioremediation". Reviews in Environmental Science and Bio/Technology. 9 (3): 215–88. doi:10.1007/s11157-010-9215-6. S2CID 85268562.

[Disadv-Factors-49] Boopathy, R (2000). "Factors limiting bioremediation technologies". Bioresource Technology. 74: 63–7. doi:10.1016/S0960-8524(99)00144-3.

[Disadv-EncTox-50] Wexler, editor-in-chief, Philip (2014). Encyclopedia of toxicology (3rd ed.). San Diego, Ca: Academic Press Inc. p. 489. ISBN 9780123864543. {{cite book}}: |first1= has generic name (help)CS1 maint: multiple names: authors list (link)

[51] Maymó-Gatell, Xavier; Chien, Yueh-tyng; Gossett, James M.; Zinder, Stephen H. (1997-06-06). "Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene". Science. 276 (5318): 1568–1571. doi:10.1126/science.276.5318.1568. ISSN 0036-8075. PMID 9171062.

[Disadv-Overview-52] Vidali, M. (2001). "Bioremediation. An overview" (PDF). Pure and Applied Chemistry. 73 (7): 1163–72. doi:10.1351/pac200173071163. S2CID 18507182.

[53] Sharma, Jot (2019). "Advantages and Limitations of In Situ Methods of Bioremediation". Recent Adv Biol Med. 5 (2019): 10941. doi:10.18639/RABM.2019.955923.

[:12-54] Odukkathil, Greeshma; Vasudevan, Namasivayam (2013). "Toxicity and bioremediation of pesticides in agricultural soil". Reviews in Environmental Science and Bio/Technology. 12 (4): 421–444. doi:10.1007/s11157-013-9320-4. ISSN 1569-1705.

[55] Supreetha, K.; Rao, Saroja Narsing; Srividya, D.; Anil, H. S.; Kiran, S. (2019). "Advances in cloning, structural and bioremediation aspects of nitrile hydratases". Molecular Biology Reports. 46 (4): 4661–4673. doi:10.1007/s11033-019-04811-w. ISSN 1573-4978.

[:72-56] Sharma, Jot (2019). "Advantages and Limitations of In Situ Methods of Bioremediation". Recent Adv Biol Med. 5 (2019): 10941. doi:10.18639/RABM.2019.955923.

[57] National Service Center for Environmental Publications (2012) A Citizen's Guide to Bioremediation. https://www.epa.gov/remedytech/citizens-guide-bioremediation#:~:text=The%20Citizen's%20Guide%20series%20is,up%20contaminated%20soil%20and%20groundwater.

[pmid15040178-58] Lovley DR (October 2003). "Cleaning up with genomics: applying molecular biology to bioremediation". Nature Reviews. Microbiology. 1 (1): 35–44. doi:10.1038/nrmicro731. PMID 15040178. S2CID 40604152.

[Menn_et_al_2001-59] Menn FM, Easter JP, Sayler GS (2001). "Genetically Engineered Microorganisms and Bioremediation". Biotechnology Set. pp. 441–63. doi:10.1002/9783527620999.ch21m. ISBN 978-3-527-62099-9.

[60] Ripp S, Nivens DE, Ahn Y, Werner C, Jarrell J, Easter JP, Cox CD, Burlage RS, Sayler GS (2000). "Controlled Field Release of a Bioluminescent Genetically Engineered Microorganism for Bioremediation Process Monitoring and Control". Environmental Science & Technology. 34 (5): 846–53. Bibcode:2000EnST...34..846R. doi:10.1021/es9908319.

[Davison2005-61] Davison J (December 2005). "Risk mitigation of genetically modified bacteria and plants designed for bioremediation". Journal of Industrial Microbiology & Biotechnology. 32 (11–12): 639–50. doi:10.1007/s10295-005-0242-1. PMID 15973534. S2CID 7986980.

[62] Sayler GS, Ripp S (June 2000). "Field applications of genetically engineered microorganisms for bioremediation processes". Current Opinion in Biotechnology. 11 (3): 286–9. doi:10.1016/S0958-1669(00)00097-5. PMID 10851144.

[Irvine-63] Shanker R, Purohit HJ, Khanna P (1998). "Bioremediation for Hazardous Waste Management: The Indian Scenario". In Irvine RL, Sikdar SK (eds.). Bioremediation Technologies: Principles and Practice. pp. 81–96. ISBN 978-1-56676-561-9.

[64] Building a circular economy with synthetic biology

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 {{more citations needed|date=October 2017}}
+'''Bioremediation''' is a process used to treat [[Contamination|contaminated]] media, including water, soil and subsurface material, by altering environmental conditions to stimulate growth of [[Microorganism|microorganisms]] and degrade the target pollutants. Cases where bioremediation is commonly seen is oil spills, soils contaminated with acidic mining drainage, underground pipe leaks, and crime scene cleanups.<ref>{{Cite journal|last=Reavill|first=Gil|date=2007|title=Aftermath, INC: Cleaning up after CSI goes home|journal=Gotham books|volume=6|pages=284|issn=2007-2013}}</ref> These toxic compounds are metabolized by enzymes present in microorganisms.<ref name=":02">{{Cite journal|last=Canak|first=Stevan|last2=Berezljev|first2=Ljiljana|last3=Borojevic|first3=Krstan|last4=Asotic|first4=Jasminka|last5=Ketin|first5=Sonja|date=2019|title=Bioremediation and "green chemistry"|url=https://www.researchgate.net/publication/332318816_BIOREMEDIATION_AND_GREEN_CHEMISTRY|journal=Fresenius Environmental Bulletin|volume=28|issue=4|pages=3056-3064|via=}}</ref> Most bioremediation processes involve oxidation-reduction reactions where either an electron acceptor (commonly oxygen) is added to stimulate oxidation of a reduced pollutant (e.g. hydrocarbons) or an electron donor (commonly an organic substrate) is added to reduce oxidized pollutants (nitrate, [[perchlorate]], oxidized metals, chlorinated solvents, explosives and propellants).<ref name=":22">{{Cite book|url=https://www.epa.gov/sites/production/files/2015-04/documents/introductiontoinsitubioremediationofgroundwater_dec2013.pdf|title=Introduction to In Situ Bioremediation of Groundwater|publisher=US Environmental Protection Agency|year=2013|pages=30}}</ref> Bioremediation is used to reduce the impact of byproducts created from anthropogenic activities, such as industrialization and agricultural processes.<ref>{{Citation|last=Singh|first=Nitika|title=Role of Fungal Enzymes for Bioremediation of Hazardous Chemicals|date=2019|url=https://doi.org/10.1007/978-3-030-25506-0_9|volume=3|pages=237–256|series=Fungal Biology|place=Cham|publisher=Springer International Publishing|language=en|doi=10.1007/978-3-030-25506-0_9|isbn=978-3-030-25506-0|last2=Kumar|first2=Abhishek|last3=Sharma|first3=Bechan}}</ref> In many cases, bioremediation is less expensive and more sustainable than other [[Environmental remediation|remediation]] alternatives.<ref>{{cite web|date=June 2011|title=Green Remediation Best Management Practices: Sites with Leaking Underground Storage Tank Systems. EPA 542-F-11-008|url=https://www.epa.gov/sites/production/files/2015-04/documents/ust_gr_fact_sheet.pdf|publisher=EPA}}</ref> Other remediation techniques include, [[thermal desorption]], [[vitrification]], [[air stripping]], [[bioleaching]], [[rhizofiltration]], and soil washing. Biological treatment, bioremediation, is a similar approach used to treat wastes including wastewater, industrial waste and solid waste. The end goal of bioremediation is to remove or reduce harmful compounds to improve soil and water quality.<ref name=":02" />
-'''Bioremediation''' is a process used to treat contaminated media, including water, soil and subsurface material, by altering environmental conditions to stimulate growth of microorganisms and degrade the target pollutants. In many cases, bioremediation is less expensive and more sustainable than other [[environmental remediation|remediation]] alternatives.<ref>{{cite web|url=https://www.epa.gov/sites/production/files/2015-04/documents/ust_gr_fact_sheet.pdf|title=Green Remediation Best Management Practices: Sites with Leaking Underground Storage Tank Systems. EPA 542-F-11-008|date=June 2011|publisher=EPA}}</ref> Biological treatment is a similar approach used to treat wastes including wastewater, industrial waste and solid waste. Some environments being considered for microbial remediation include oil spills, soils contaminated with acidic mining drainage, and patches of [[plastic pollution]] in the     oceans.<ref>{{Cite book|year=2004|title=Geoenvironmental Engineering: Site Remediation, Waste Containment and Emerging Waste Management Technologies  |language=en|publisher=John Wiley & Sons |isbn=0-471-21599-6}}</ref>
-Most bioremediation processes involve oxidation-reduction reactions where either an electron acceptor (commonly oxygen) is added to stimulate oxidation of a reduced pollutant (e.g. hydrocarbons) or an electron donor (commonly an organic substrate) is added to reduce oxidized pollutants (nitrate, [[perchlorate]], oxidized metals, chlorinated solvents, explosives and propellants).<ref name=":2">{{Cite book|url=https://www.epa.gov/sites/production/files/2015-04/documents/introductiontoinsitubioremediationofgroundwater_dec2013.pdf|title=Introduction to In Situ Bioremediation of Groundwater|publisher=US Environmental Protection Agency|year=2013|pages=30}}</ref> In both these approaches, additional nutrients, vitamins, minerals, and pH buffers may be added to optimize conditions for the microorganisms. In some cases, specialized microbial cultures are added ([[bioaugmentation]]) to further enhance biodegradation. Some examples of bioremediation related technologies are [[phytoremediation]], [[mycoremediation]], [[bioventing]], [[bioleaching]], [[landfarming]], [[bioreactor]], [[composting]], [[bioaugmentation]], [[rhizofiltration]], and [[biostimulation]].
+Contaminants can be removed or reduced with varying bioremediation techniques that are ''[[In situ|in-situ]]'' or ''[[Ex situ conservation|ex-situ]]''.<ref name=":42">{{Cite journal|last=Kapahi|first=Meena|last2=Sachdeva|first2=Sarita|date=2019|title=Bioremediation Options for Heavy Metal Pollution|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6905138/|journal=Journal of Health & Pollution|volume=9|issue=24|doi=10.5696/2156-9614-9.24.191203|issn=2156-9614|pmc=6905138|pmid=31893164}}</ref> Bioremediation techniques are classified based on the treatment locality.<ref name=":7">{{Cite journal|last=Sharma|first=Jot|date=2019|title=Advantages and Limitations of In Situ Methods of Bioremediation|url=https://rabm.scholasticahq.com/article/10941-advantages-and-limitations-of-in-situ-methods-of-bioremediation|journal=Recent Adv Biol Med|language=en|volume=5|issue=2019|pages=10941|doi=10.18639/RABM.2019.955923}}</ref> ''In-situ'' techniques treats polluted sites in a non-destructive manner and cost-effective. Whereas, ''ex-situ'' techniques commonly require the contaminated site to be excavated which increases costs.<ref>{{Cite journal|last=Kensa|first=V. Mary|date=2011|title=BIOREMEDIATION - AN OVERVIEW|url=https://www.icontrolpollution.com/%20peer-reviewed/%20bioremediation-an-overview-37408.html|journal=I Control Pollution|language=en|volume=27|issue=2|pages=161–168|issn=0970-2083}}</ref> In both these approaches, additional nutrients, vitamins, minerals, and pH buffers may be added to optimize conditions for the microorganisms. In some cases, specialized microbial cultures are added ([[Bioaugmentation|biostimulation]]) to further enhance [[biodegradation]]. Some examples of bioremediation related technologies are [[phytoremediation]], [[bioventing]], bioattenuation, [[biosparging]], [[composting]] (biopiles and windrows), and [[landfarming]].
-== Microbial Consortium ==
-Bioremediation utilizing microbes works through the use of a [[microbial consortium]].  In this context a microbial consortium is a symbiotically associated population of microbes that survive by utilizing the secondary metabolites of the species around them. An individual species of microbes is generally incapable of fully breaking down complex molecules, but may be able to partially degrade a compound. Another part of that partially digested molecule may be broken down by another species in the consortia, a pattern that can be repeated until the environmental contaminant is broken down into harmless byproducts. <ref>{{Citation|last1=Paniagua-Michel|first1=J.|title=Microbial Consortia and Biodegradation of Petroleum Hydrocarbons in Marine Environments|date=2018|url=http://link.springer.com/10.1007/978-981-13-1840-5_1|work=Microbial Action on Hydrocarbons|pages=1–20|editor-last=Kumar|editor-first=Vivek|place=Singapore|publisher=Springer Singapore|language=en|doi=10.1007/978-981-13-1840-5_1|isbn=978-981-13-1839-9|access-date=2021-03-03|last2=Fathepure|first2=Babu Z.|editor2-last=Kumar|editor2-first=Manoj|editor3-last=Prasad|editor3-first=Ram}}</ref>
 ==Chemistry==
@@ Line 29: / Line 26: @@
 |}
-==Aerobic==
+== Aerobic ==
-Aerobic bioremediation is the most common form of oxidative bioremediation process where oxygen is provided as the electron acceptor for oxidation of [[petroleum]], [[Polycyclic aromatic hydrocarbon|polyaromatic hydrocarbons]] (PAHs), [[phenols]], and other reduced pollutants. Oxygen is generally the preferred electron acceptor because of the higher energy yield and because oxygen is required for some enzyme systems to initiate the degradation process.<ref name=":3">{{Cite book|title=Handbook of Bioremediation|last=Norris|first=Robert|publisher=CRC Press|year=1993|isbn=9781351363457|pages=45}}</ref>  Numerous laboratory and field studies have shown that microorganisms can degrade a wide variety of hydrocarbons, including components of gasoline, kerosene, diesel, and jet fuel. Under ideal conditions, the biodegradation rates of the low- to moderate-weight [[Aliphatic compound|aliphatic]], [[Alicyclic compound|alicyclic]], and [[Aromatic hydrocarbon|aromatic]] compounds can be very high. As the molecular weight of the compound increases, so does the resistance to biodegradation.<ref name=":3" />
+== ''In-situ techniques'' ==
+[[File:In Situ Bioremediation.png|thumb|Visual representation showing ''in-situ'' bioremediation. This process involves the addition of oxygen, nutrients, or microbes into contaminated soil to remove toxic pollutants.<ref name=":02" /> Contamination includes buried waste and underground pipe leakage that infiltrate ground water systems.<ref>{{Citation|last=Jørgensen|first=Kirsten S.|title=In Situ Bioremediation|date=2007|url=https://www.sciencedirect.com/science/article/pii/S0065216406610083|work=Advances in Applied Microbiology|volume=61|pages=285–305|publisher=Academic Press|language=en|doi=10.1016/S0065-2164(06)61008-3|access-date=}}</ref> The addition of oxygen removes the pollutants by producing carbon dioxide and water.<ref name=":4">{{Cite journal|last=Kapahi|first=Meena|last2=Sachdeva|first2=Sarita|date=2019|title=Bioremediation Options for Heavy Metal Pollution|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6905138/|journal=Journal of Health & Pollution|volume=9|issue=24|doi=10.5696/2156-9614-9.24.191203|issn=2156-9614|pmc=6905138|pmid=31893164}}</ref>]]
+==== Bioventing ====
+[[null|link=|thumb]]
+Bioventing is a process that increases the oxygen or air flow into the unsaturated zone of the soil which increases the rate of natural in situ degradation of the targeted hydrocarbon contaminant.<ref>{{Cite journal|last=Frutos|first=F. Javier García|last2=Escolano|first2=Olga|last3=García|first3=Susana|last4=Babín|first4=Mar|last5=Fernández|first5=M. Dolores|date=2010|title=Bioventing remediation and ecotoxicity evaluation of phenanthrene-contaminated soil|journal=Journal of Hazardous Materials|volume=183|issue=1–3|pages=806–813|doi=10.1016/j.jhazmat.2010.07.098|issn=0304-3894}}</ref> Bioventing, an aerobic bioremediation, is the most common form of oxidative bioremediation process where oxygen is provided as the electron acceptor for oxidation of [[petroleum]], [[Polycyclic aromatic hydrocarbon|polyaromatic hydrocarbons]] (PAHs), [[phenols]], and other reduced pollutants. Oxygen is generally the preferred electron acceptor because of the higher energy yield and because oxygen is required for some enzyme systems to initiate the degradation process.<ref name=":32">{{Cite book|last=Norris|first=Robert|title=Handbook of Bioremediation|publisher=CRC Press|year=1993|isbn=9781351363457|pages=45}}</ref> Microorganisms can degrade a wide variety of hydrocarbons, including components of gasoline, kerosene, diesel, and jet fuel. Under ideal aerobic conditions, the biodegradation rates of the low- to moderate-weight [[Aliphatic compound|aliphatic]], [[Alicyclic compound|alicyclic]], and [[Aromatic hydrocarbon|aromatic]] compounds can be very high. As the molecular weight of the compound increases, so does the resistance to biodegradation.<ref name=":32" /> This results in higher contaminated volatile compounds, due to their high molecular weight, are more difficult to remove from the environment.
+Most bioremediation processes involve oxidation-reduction reactions where either an electron acceptor (commonly oxygen) is added to stimulate oxidation of a reduced pollutant (e.g. hydrocarbons) or an electron donor (commonly an organic substrate) is added to reduce oxidized pollutants (nitrate, [[perchlorate]], oxidized metals, chlorinated solvents, explosives and propellants).<ref name=":2">{{Cite book|url=https://www.epa.gov/sites/production/files/2015-04/documents/introductiontoinsitubioremediationofgroundwater_dec2013.pdf|title=Introduction to In Situ Bioremediation of Groundwater|publisher=US Environmental Protection Agency|year=2013|pages=30}}</ref> In both these approaches, additional nutrients, vitamins, minerals, and pH buffers may be added to optimize conditions for the microorganisms. In some cases, specialized microbial cultures are added ([[bioaugmentation]]) to further enhance biodegradation.
 Common approaches for providing oxygen above the water table include [[landfarming]], [[compost]]ing and [[bioventing]]. During landfarming, contaminated soils, sediments, or sludges are incorporated into the soil surface and periodically turned over (tilled) using conventional agricultural equipment to aerate the mixture.  Composting accelerates pollutant biodegradation by mixing the waste to be treated with a bulking agent, forming into piles, and periodically mixed to increase oxygen transfer.  [[Bioventing]] is a process that increases the oxygen or air flow into the unsaturated zone of the soil which increases the rate of natural in situ degradation of the targeted hydrocarbon contaminant.<ref>{{Cite journal|last1=Frutos|first1=F. Javier García|last2=Escolano|first2=Olga|last3=García|first3=Susana|last4=Babín|first4=Mar|last5=Fernández|first5=M. Dolores|date=November 2010|title=Bioventing remediation and ecotoxicity evaluation of phenanthrene-contaminated soil|journal=Journal of Hazardous Materials|volume=183|issue=1–3|pages=806–813|doi=10.1016/j.jhazmat.2010.07.098|pmid=20800967|issn=0304-3894}}</ref>
-Approaches for oxygen addition below the water table include recirculating aerated water through the treatment zone, addition of pure oxygen or peroxides, and [[air sparging]]. Recirculation systems typically consist of a combination of injection wells or galleries and one or more recovery wells where the extracted groundwater is treated, oxygenated, amended with nutrients and reinjected.  However, the amount of oxygen that can be provided by this method is limited by the low solubility of oxygen in water (8 to 10&nbsp;mg/L for water in equilibrium with air at typical temperatures).  Greater amounts of oxygen can be provided by contacting the water with pure oxygen or addition of [[hydrogen peroxide]] (H<sub>2</sub>O<sub>2</sub>) to the water.  In some cases, slurries of solid calcium or magnesium peroxide are injected under pressure through soil borings.  These solid peroxides react with water releasing H<sub>2</sub>O<sub>2</sub> which then decomposes releasing oxygen.  Air sparging involves the injection of air under pressure below the water table.  The air injection pressure must be great enough to overcome the hydrostatic pressure of the water and resistance to air flow through the soil.<ref>{{Cite book|title=Air Sparging Design Paradigm|last=Leeson|first=Andrea|publisher=BATTELLE COLUMBUS OH|year=2002|location=http://www.dtic.mil/get-tr-doc/pdf?AD=ADA492279}}</ref>
+Approaches for oxygen addition below the water table include recirculating aerated water through the treatment zone, addition of pure oxygen or peroxides, and [[air sparging]]. Recirculation systems typically consist of a combination of injection wells or galleries and one or more recovery wells where the extracted groundwater is treated, oxygenated, amended with nutrients and re-injected.  However, the amount of oxygen that can be provided by this method is limited by the low solubility of oxygen in water (8 to 10 mg/L for water in equilibrium with air at typical temperatures). Greater amounts of oxygen can be provided by contacting the water with pure oxygen or addition of [[hydrogen peroxide]] (H<sub>2</sub>O<sub>2</sub>) to the water. In some cases, slurries of solid calcium or magnesium peroxide are injected under pressure through soil borings. These solid peroxides react with water releasing H<sub>2</sub>O<sub>2</sub> which then decomposes releasing oxygen. Air sparging involves the injection of air under pressure below the water table. The air injection pressure must be great enough to overcome the hydrostatic pressure of the water and resistance to air flow through the soil.<ref>{{Cite book|title=Air Sparging Design Paradigm|last=Leeson|first=Andrea|publisher=BATTELLE COLUMBUS OH|year=2002|location=http://www.dtic.mil/get-tr-doc/pdf?AD=ADA492279}}</ref>
+==== Biostimulation ====
-==Anaerobic==
+Bioremediation can be carried out by bacteria that is naturally present in the environment or adding nutrients, this process is called biostimulation.<ref name=":43">{{Cite journal|last=Kapahi|first=Meena|last2=Sachdeva|first2=Sarita|date=2019|title=Bioremediation Options for Heavy Metal Pollution|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6905138/|journal=Journal of Health & Pollution|volume=9|issue=24|doi=10.5696/2156-9614-9.24.191203|issn=2156-9614|pmc=6905138|pmid=31893164}}</ref>
-Anaerobic bioremediation can be employed to treat a broad range of oxidized contaminants including chlorinated ethenes ([[Tetrachloroethylene|PCE]], [[Trichloroethylene|TCE]], [[Dichloroethene|DCE]], [[Vinyl chloride|VC)]], chlorinated ethanes ([[Trichloroethane|TCA]], [[Dichloroethane|DCA]]), chloromethanes ([[Carbon tetrachloride|CT]], [[Chloroform|CF]]), chlorinated cyclic hydrocarbons, various energetics (e.g., [[perchlorate]],<ref>{{cite book|title=In situ bioremediation of perchlorate in groundwater|last1=Coates|first1=J.D.|last2=Jackson|first2=W.A.|date=2008|publisher=Springer|isbn=978-0-387-84921-8|editor1-last=Stroo|editor1-first=Hans|location=New York|pages=29–53|chapter=Principles of perchlorate treatment|doi=10.1007/978-0-387-84921-8_3|name-list-style=vanc|editor2-last=Ward|editor2-first=C. Herb}}</ref> [[RDX]], [[TNT]]), and [[nitrate]].<ref name=":4" />  This process involves the addition of an electron donor to: 1) deplete background electron acceptors including oxygen, nitrate, oxidized iron and manganese and sulfate; and 2) stimulate the biological and/or chemical reduction of the oxidized pollutants.  [[Hexavalent chromium]] (Cr[VI]) and uranium (U[VI]) can be reduced to less mobile and/or less toxic forms (e.g., Cr[III], U[IV]). Similarly, reduction of sulfate to sulfide (sulfidogenesis) can be used to precipitate certain metals (e.g., [[zinc]], [[cadmium]]). The choice of substrate and the method of injection depend on the contaminant type and distribution in the aquifer, hydrogeology, and remediation objectives. Substrate can be added using conventional well installations, by direct-push technology, or by excavation and backfill such as [[permeable reactive barrier]]s (PRB) or biowalls. Slow-release products composed of edible oils or solid substrates tend to stay in place for an extended treatment period. Soluble substrates or soluble fermentation products of slow-release substrates can potentially migrate via advection and diffusion, providing broader but shorter-lived treatment zones. The added organic substrates are first fermented to hydrogen (H<sub>2</sub>) and volatile fatty acids (VFAs). The VFAs, including acetate, lactate, propionate and butyrate, provide carbon and energy for bacterial metabolism.<ref name=":4">{{Cite book|title=Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents.|publisher=Air Force Center for Environmental Excellence, TX, Naval Facilities Engineering Service Center, CA and Environmental Security Technology Certification Program, VA.|year=2004}}</ref><ref name=":2" />
+Bacteria, also known as microbia, are naturally occurring in the environment and are used to degrade hydrocarbons.<ref>{{Cite journal|last=Lee|first=Dong Wan|last2=Lee|first2=Hanbyul|last3=Lee|first3=Aslan Hwanhwi|last4=Kwon|first4=Bong-Oh|last5=Khim|first5=Jong Seong|last6=Yim|first6=Un Hyuk|last7=Kim|first7=Beom Seok|last8=Kim|first8=Jae-Jin|date=2018|title=Microbial community composition and PAHs removal potential of indigenous bacteria in oil contaminated sediment of Taean coast, Korea|url=https://www.sciencedirect.com/science/article/pii/S026974911733871X|journal=Environmental Pollution|language=en|volume=234|pages=503–512|doi=10.1016/j.envpol.2017.11.097|issn=0269-7491}}</ref> Many biological processes are sensitive to pH and function most efficiently in near neutral conditions. Low pH can interfere with pH homeostasis or increase the solubility of toxic metals. Microorganisms can expend cellular energy to maintain homeostasis or cytoplasmic conditions may change in response to external changes in pH. Anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis.<ref>{{cite book|last1=Slonczewski|first1=J.L.|title=Encyclopedia of microbiology|date=2009|publisher=Elsevier|isbn=978-0-12-373944-5|editor1-last=Schaechter|editor1-first=Moselio|edition=3rd|pages=477–484|chapter=Stress Responses: pH|doi=10.1016/B978-012373944-5.00100-0}}</ref>
-==Heavy metals==
-Heavy metals including cadmium, chromium, lead and uranium are elements so they cannot be biodegraded. However, bioremediation processes can potentially be used to reduce the mobility of these material in the subsurface, reducing the potential for human and environmental exposure. The mobility of certain metals including chromium (Cr) and uranium (U) varies depending on the oxidation state of the material.<ref>{{Cite book|url=https://enviro.wiki/images/c/c1/USEPA-2007-MNA_of_Inorganic_Contaminants_in_GW%2C_Vol_1_Technical_Basis_for_Assessment.pdf|title=Monitored natural attenuation of inorganic contaminants in groundwater, Volume 1 Technical basis for assessment|last=R.G. Ford, R.T. Wilkin, and R.W. Puls|publisher=U.S. Environmental Protection Agency, EPA/600/R-07/139|year=2007|oclc=191800707}}</ref>  Microorganisms can be used to reduce the toxicity and mobility of chromium by reducing hexavalent chromium, Cr(VI) to trivalent Cr (III).<ref>{{Cite book|url=https://enviro.wiki/images/3/3a/USEPA-2007-MNA_of_Inorganic_Contaminants_in_GW%2C_Vol_2.pdf|title=Monitored Natural Attenuation of Inorganic Contaminants in Groundwater, Volume 2 - Assessment for Non-Radionulcides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium|last=R.G. Ford, R.T. Wilkin, and R.W. Puls|publisher=USEPA|year=2007}}</ref>  Uranium can be reduced from the more mobile U(VI) oxidation state to the less mobile U(IV) oxidation state.<ref>{{cite journal|vauthors=Williams KH, Bargar JR, Lloyd JR, Lovley DR|date=June 2013|title=Bioremediation of uranium-contaminated groundwater: a systems approach to subsurface biogeochemistry|journal=Current Opinion in Biotechnology|volume=24|issue=3|pages=489–97|doi=10.1016/j.copbio.2012.10.008|pmid=23159488}}</ref><ref>{{Cite book|url=https://enviro.wiki/images/0/05/USEPA-2010-MNA_of_Inorganic_Contaminants_in_GW%2C_Vol_3.pdf|title=Monitored natural attenuation of inorganic contaminants in groundwater, Volume 3 Assessment for Radionuclides Including Tritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium|last=R.G. Ford and R.T. Wilkin|publisher=U.S. Environmental Protection Agency, EPA/600/R-10/093|year=2007}}</ref>  Microorganisms are used in this process because the reduction rate of these metals is often slow unless catalyzed by microbial interactions<ref name=":0">{{Cite book|title=Bioremediation of Metals and Radionuclides : What It Is and How It Works (2nd Edition).|last=Anna.|first=Hazen, Terry. Palmisano|date=2003|publisher=Lawrence Berkeley National Laboratory|oclc=316485842}}</ref>  Research is also underway to develop methods to remove metals from water by enhancing the sorption of the metal to cell walls.<ref name=":0" />  This approach has been evaluated for treatment of cadmium,<ref name="source 3">{{cite journal|vauthors=Ansari MI, Malik A|date=November 2007|title=Biosorption of nickel and cadmium by metal resistant bacterial isolates from agricultural soil irrigated with industrial wastewater|journal=Bioresource Technology|volume=98|issue=16|pages=3149–53|doi=10.1016/j.biortech.2006.10.008|pmid=17166714}}</ref> chromium,<ref name=":1">{{cite journal|vauthors=Durán U, Coronado-Apodaca KG, Meza-Escalante ER, Ulloa-Mercado G, Serrano D|date=May 2018|title=Two combined mechanisms responsible to hexavalent chromium removal on active anaerobic granular consortium|journal=Chemosphere|volume=198|pages=191–197|bibcode=2018Chmsp.198..191D|doi=10.1016/j.chemosphere.2018.01.024|pmid=29421729}}</ref> and lead.<ref name="source 1">{{cite journal|vauthors=Tripathi M, Munot HP, Shouche Y, Meyer JM, Goel R|date=May 2005|title=Isolation and functional characterization of siderophore-producing lead- and cadmium-resistant Pseudomonas putida KNP9|journal=Current Microbiology|volume=50|issue=5|pages=233–7|doi=10.1007/s00284-004-4459-4|pmid=15886913|s2cid=21061197}}</ref>  [[Phytoextraction process]]es concentrate contaminants in the biomass for subsequent removal.
+Bioremediation utilizing microbes works through the use of a [[microbial consortium]]. In this context, a microbial consortium is a symbiotically associated population of microbes that survive by utilizing the secondary metabolites of the species around them. An individual species of microbes is generally incapable of fully breaking down complex molecules, but may be able to partially degrade a compound. Another part of that partially digested molecule may be broken down by another species in the consortia, a pattern that can be repeated until the environmental contaminant is broken down into harmless byproducts.<ref>{{Citation|last1=Paniagua-Michel|first1=J.|title=Microbial Consortia and Biodegradation of Petroleum Hydrocarbons in Marine Environments|date=2018|url=http://link.springer.com/10.1007/978-981-13-1840-5_1|work=Microbial Action on Hydrocarbons|pages=1–20|editor-last=Kumar|editor-first=Vivek|place=Singapore|publisher=Springer Singapore|language=en|doi=10.1007/978-981-13-1840-5_1|isbn=978-981-13-1839-9|access-date=2021-03-03|last2=Fathepure|first2=Babu Z.|editor2-last=Kumar|editor2-first=Manoj|editor3-last=Prasad|editor3-first=Ram}}</ref>
-== Additives ==
+[[File:Bioremediation at INL.jpg|thumb|An example of biostimulation at the Snake River Plain Aquifer in Idaho. This process involves the addition of whey powder to promote the utilization of naturally present bacteria. Whey powder acts as a substrate to aid in the growth of bacteria.<ref>{{Cite journal|last=Mora|first=Rebecca H.|last2=Macbeth|first2=Tamzen W.|last3=MacHarg|first3=Tara|last4=Gundarlahalli|first4=Jagadish|last5=Holbrook|first5=Holly|last6=Schiff|first6=Paul|date=2008|title=Enhanced bioremediation using whey powder for a trichloroethene plume in a high-sulfate, fractured granitic aquifer|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/rem.20168|journal=Remediation Journal|language=en|volume=18|issue=3|pages=7–30|doi=10.1002/rem.20168|issn=1520-6831}}</ref> At this site, microorganisms break down the carcinogenic compound [[trichloroethylene]] (TCE), which is a process seen in previous studies.<ref>{{Cite journal|last=Mora|first=Rebecca H.|last2=Macbeth|first2=Tamzen W.|last3=MacHarg|first3=Tara|last4=Gundarlahalli|first4=Jagadish|last5=Holbrook|first5=Holly|last6=Schiff|first6=Paul|date=2008|title=Enhanced bioremediation using whey powder for a trichloroethene plume in a high-sulfate, fractured granitic aquifer|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/rem.20168|journal=Remediation Journal|language=en|volume=18|issue=3|pages=7–30|doi=10.1002/rem.20168|issn=1520-6831}}</ref>]]
-In the event of biostimulation, adding nutrients that are limited to make the environment more suitable for bioremediation, nutrients such as nitrogen, phosphorus, oxygen, and carbon may be added to the system to improve effectiveness of the treatment.{{cn|date=March 2021}}
+In the event of biostimulation, adding nutrients that are limited to make the environment more suitable for bioremediation, nutrients such as nitrogen, phosphorus, oxygen, and carbon may be added to the system to improve effectiveness of the treatment.<ref>{{Cite journal|last=Adams|first=Omokhagbor|date=February 28, 2015|title=Bioremediation, Biostimulation and Bioaugmentation: A Review|url=https://www.researchgate.net/publication/277216237|journal=International Journal of Environmental Bioremediation and Biodegredation|volume=3|issue=1|pages=28–39|via=Research Gate}}</ref> Nutrients are required for the biodegradation of oil pollution and can be used to reduce the negative output on the environment.<ref>{{Cite journal|last=Chen|first=Qingguo|last2=Bao|first2=Bo|last3=Li|first3=Yijing|last4=Liu|first4=Mei|last5=Zhu|first5=Baikang|last6=Mu|first6=Jun|last7=Chen|first7=Zhi|date=2020|title=Effects of marine oil pollution on microbial diversity in coastal waters and stimulating indigenous microorganism bioremediation with nutrients|url=https://www.sciencedirect.com/science/article/pii/S2352485520305235|journal=Regional Studies in Marine Science|language=en|volume=39|pages=101395|doi=10.1016/j.rsma.2020.101395|issn=2352-4855}}</ref> Specific to marine oil spills, nitrogen and phosphorus have been key nutrients in biodegradation.<ref>{{Cite journal|last=Varjani|first=Sunita J.|last2=Upasani|first2=Vivek N.|date=2017|title=A new look on factors affecting microbial degradation of petroleum hydrocarbon pollutants|url=https://www.sciencedirect.com/science/article/pii/S0964830516308113|journal=International Biodeterioration & Biodegradation|language=en|volume=120|pages=71–83|doi=10.1016/j.ibiod.2017.02.006|issn=0964-8305}}</ref>
-Many biological processes are sensitive to pH and function most efficiently in near neutral conditions.  Low pH can interfere with pH homeostasis or increase the solubility of toxic metals. Microorganisms can expend cellular energy to maintain homeostasis or cytoplasmic conditions may change in response to external changes in pH.  Some anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis.<ref>{{cite book|last1=Slonczewski|first1=J.L.|editor1-last=Schaechter|editor1-first=Moselio|title=Encyclopedia of microbiology|date=2009|publisher=Elsevier|isbn=978-0-12-373944-5|pages=477–484|edition=3rd|chapter=Stress Responses: pH|doi=10.1016/B978-012373944-5.00100-0}}</ref>
+Many biological processes are sensitive to pH and function most efficiently in near neutral conditions. Low pH can interfere with pH homeostasis or increase the solubility of toxic metals. Microorganisms can expend cellular energy to maintain homeostasis or cytoplasmic conditions may change in response to external changes in pH.  Some anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis.<ref>{{cite book|last1=Slonczewski|first1=J.L.|title=Encyclopedia of microbiology|date=2009|publisher=Elsevier|isbn=978-0-12-373944-5|editor1-last=Schaechter|editor1-first=Moselio|edition=3rd|pages=477–484|chapter=Stress Responses: pH|doi=10.1016/B978-012373944-5.00100-0}}</ref>
+Anaerobic bioremediation can be employed to treat a broad range of oxidized contaminants including chlorinated ethenes ([[Tetrachloroethylene|PCE]], [[Trichloroethylene|TCE]], [[Dichloroethene|DCE]], [[Vinyl chloride|VC)]], chlorinated ethanes ([[Trichloroethane|TCA]], [[Dichloroethane|DCA]]), chloromethanes ([[Carbon tetrachloride|CT]], [[Chloroform|CF]]), chlorinated cyclic hydrocarbons, various energetics (e.g., [[perchlorate]],<ref>{{cite book|last1=Coates|first1=J.D.|title=In situ bioremediation of perchlorate in groundwater|last2=Jackson|first2=W.A.|date=2008|publisher=Springer|isbn=978-0-387-84921-8|editor1-last=Stroo|editor1-first=Hans|location=New York|pages=29–53|chapter=Principles of perchlorate treatment|doi=10.1007/978-0-387-84921-8_3|editor2-last=Ward|editor2-first=C. Herb|name-list-style=vanc}}</ref> [[RDX]], [[TNT]]), and [[nitrate]].<ref name=":4" /> This process involves the addition of an electron donor to: 1) deplete background electron acceptors including oxygen, nitrate, oxidized iron and manganese and sulfate; and 2) stimulate the biological and/or chemical reduction of the oxidized pollutants.  [[Hexavalent chromium]] (Cr[VI]) and uranium (U[VI]) can be reduced to less mobile and/or less toxic forms (e.g., Cr[III], U[IV]). Similarly, reduction of sulfate to sulfide (sulfidogenesis) can be used to precipitate certain metals (e.g., [[zinc]], [[cadmium]]). The choice of substrate and the method of injection depend on the contaminant type and distribution in the aquifer, hydrogeology, and remediation objectives. Substrate can be added using conventional well installations, by direct-push technology, or by excavation and backfill such as [[permeable reactive barrier]]s (PRB) or biowalls. Slow-release products composed of edible oils or solid substrates tend to stay in place for an extended treatment period. Soluble substrates or soluble fermentation products of slow-release substrates can potentially migrate via advection and diffusion, providing broader but shorter-lived treatment zones. The added organic substrates are first fermented to hydrogen (H<sub>2</sub>) and volatile fatty acids (VFAs). The VFAs, including acetate, lactate, propionate and butyrate, provide carbon and energy for bacterial metabolism.<ref name=":4" /><ref name=":2" />
+==== Bioattenuation ====
+During bioattenuation, biodegradation occurs naturally with the addition of nutrients or bacteria. The indigenous microbes present will determine the metabolic activity and act as a natural attenuation.<ref name=":5">{{Citation|last=Ying|first=Guang-Guo|title=Chapter 14 - Remediation and Mitigation Strategies|date=2018|url=https://www.sciencedirect.com/science/article/pii/B9780128161555000142|work=Integrated Analytical Approaches for Pesticide Management|pages=207–217|publisher=Academic Press|language=en|doi=10.1016/b978-0-12-816155-5.00014-2|isbn=978-0-12-816155-5}}</ref> While there is no anthropogenic involvement in bioattenuation, the contaminated site must still be monitored.<ref name=":5" />
+==== Biosparging ====
+Biosparging is the process of groundwater remediation as oxygen, and possible nutrients, is injected. When oxygen is injected, indigenous bacteria are stimulated to increase rate of degradation.<ref>{{Cite journal|last=Vidali|first=M|date=2001|title=Bioremediation. An overview*|url=https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.1073.5610&rep=rep1&type=pdf|journal=Pure and Applied Chemistry|volume=73|issue=7|pages=1163-1172}}</ref> However, biosparging focuses on saturated contaminated zones, specifically related to ground water remediation.<ref>{{Cite journal|last=Johnson|first=Paul C.|last2=Johnson|first2=Richard L.|last3=Bruce|first3=Cristin L.|last4=Leeson|first4=Andrea|date=2001|title=Advances in In Situ Air Sparging/Biosparging|url=https://doi.org/10.1080/20018891079311|journal=Bioremediation Journal|volume=5|issue=4|pages=251–266|doi=10.1080/20018891079311|issn=1088-9868}}</ref>
+== ''Ex-situ'' techniques ==
+==== Biopiles ====
+Biopiles, similar to bioventing, are used to reduce petroleum pollutants by introducing aerobic hydrocarbons to contaminated soils. However, the soil is excavated and piled with an aeration system. This aeration system enhances microbial activity by introducing oxygen under positive pressure or removes oxygen under negative pressure.<ref>{{Cite journal|last=Emami|first=Somayeh|last2=Pourbabaee|first2=Ahmad Ali|last3=Alikhani|first3=Hossein Ali|date=2012|title=Bioremediation Principles and Techniques on Petroleum Hydrocarbon Contaminated Soil|journal=Technical Journal of Engineering and Applied Sciences|volume=2|issue=10|pages=320-323|issn=2051-0853}}</ref>
+==== Windrows ====
+[[File:Shell Haven East Site - geograph.org.uk - 591937.jpg|thumb|The former Shell Haven Refinery in Standford-le-Hope which underwent bioremediation to reduce the oil contaminated site. Bioremediation techniques, such as windrows, were used to promote oxygen transfer.<ref>{{Cite book|last=Waters|first=J.M|title=Redevelopment of the former Shell Haven refinery|last2=Lambert|first2=C|last3=Reid|first3=D|last4=Shaw|first4=R|publisher=WIT Press|year=2002|isbn=1-85312-918-6|location=Southampton, UK|pages=77-85}}</ref> The refinery has excavated approximately 115,000m<sup>3</sup> of contaminated soil.<ref>{{Cite book|last=Waters|first=J.M|title=Redevelopment of the former Shell Haven refinery|last2=Lambert|first2=C|last3=Reid|first3=D|last4=Shaw|first4=R|publisher=WIT Press|year=2002|isbn=1-85312-918-6|location=Southampton, UK|pages=77-85}}</ref>]]
+Windrow systems are similar to compost techniques where soil is periodically turned in order to enhance aeration.<ref>{{Cite book|last=Rakshit|first=Amitava|url=https://books.google.ca/books?hl=en&lr=&id=H-IaEAAAQBAJ&oi=fnd&pg=PA37&dq=bioremediation+windrow&ots=BwI_isWIRU&sig=QygTqYkkcuILmvfWt3PzcMNepFA&redir_esc=y#v=onepage&q=bioremediation%20windrow&f=false|title=Bioremediation Science: From Theory to Practice|last2=Parihar|first2=Manoj|last3=Sarkar|first3=Binoy|last4=Singh|first4=Harikesh B.|last5=Fraceto|first5=Leonardo Fernandes|date=2021|publisher=CRC Press|isbn=978-1-000-28046-3|language=en}}</ref> This periodic turning also allows contaminants present in the soil to be uniformly distributed which accelerates the process of bioremediation.<ref>{{Cite journal|last=Azubuike|first=Christopher Chibueze|last2=Chikere|first2=Chioma Blaise|last3=Okpokwasili|first3=Gideon Chijioke|date=2016|title=Bioremediation techniques–classification based on site of application: principles, advantages, limitations and prospects|url=https://doi.org/10.1007/s11274-016-2137-x|journal=World Journal of Microbiology and Biotechnology|language=en|volume=32|issue=11|pages=180|doi=10.1007/s11274-016-2137-x|issn=1573-0972|pmc=PMC5026719|pmid=27638318}}</ref>
+==== Landfarming ====
+Landfarming, or land treatment, is a method commonly used for sludge spills. This method disperses contaminated soil and aerates the soil by cyclically rotating.<ref>{{Citation|last=Kumar|first=Vineet|title=Bioremediation: An Eco-sustainable Approach for Restoration of Contaminated Sites|date=2018|url=https://doi.org/10.1007/978-981-13-0053-0_6|work=Microbial Bioprospecting for Sustainable Development|pages=115–136|place=Singapore|publisher=Springer|language=en|doi=10.1007/978-981-13-0053-0_6|isbn=978-981-13-0053-0|access-date=|last2=Shahi|first2=S. K.|last3=Singh|first3=Simranjeet}}</ref> This process is an above land application and contaminated soils are required to be shallow in order for microbial activity to be stimulated. However, if the contamination is deeper than 5 feet, then the soil is required to be excavated to above ground.<ref>United States Environmental Protection Agency (USEPA) (2017) How To Evaluate Alternative Cleanup Technologies For Underground Storage Tank Sites. A Guide For Corrective Action Plan Reviewers. EPA 510-B-17-003. https://www.epa.gov/sites/production/files/2014-03/documents/tum_ch5.pdf</ref>
+==Heavy metals==
+Heavy metals become present in the environment due to anthropogenic activities or natural factors.<ref name=":44">{{Cite journal|last=Kapahi|first=Meena|last2=Sachdeva|first2=Sarita|date=2019|title=Bioremediation Options for Heavy Metal Pollution|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6905138/|journal=Journal of Health & Pollution|volume=9|issue=24|doi=10.5696/2156-9614-9.24.191203|issn=2156-9614|pmc=6905138|pmid=31893164}}</ref> Anthropogenic activities include industrial emissions, electronic waste, and ore mining. Natural factors include mineral weathering, soil erosion and forest fires.<ref name=":6">{{Cite journal|last=Kapahi|first=Meena|last2=Sachdeva|first2=Sarita|date=2019|title=Bioremediation Options for Heavy Metal Pollution|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6905138/|journal=Journal of Health & Pollution|volume=9|issue=24|doi=10.5696/2156-9614-9.24.191203|issn=2156-9614|pmc=6905138|pmid=31893164}}</ref> Heavy metals including cadmium, chromium, lead and uranium are unlike organic compounds and cannot be biodegraded. However, bioremediation processes can potentially be used to reduce the mobility of these material in the subsurface, reducing the potential for human and environmental exposure.<ref>{{Cite journal|last=Ghosh|first=M|last2=Singh|first2=S.P|date=2005|title=A Review on Phytoremediation of Heavy Metals and Utilization of It’s by Products|url=https://d1wqtxts1xzle7.cloudfront.net/37997269/A_review_on_phytoremediation_of_heavy_metals_and_utilisation_of_it_s_by_products.pdf?1435205854=&response-content-disposition=inline%3B+filename%3DA_review_on_phytoremediation_of_heavy_me.pdf&Expires=1616733323&Signature=IGzeN-9bz6rkSIrIGMA7eGC3O~a3DM82eVreO2YN-5R8mjG~72O7GgfWyQlzEj-XlB3~ELh15h7-llj-bzAP1vzgCX~uzInEdiRql23JHvAALbVcVZKR4QE9MWC78Gj3IY5KOr~wj1RoXjdT0g3G6wohnNpFb62DqZOsbeHmBZphjFTjh3If738NFgH1gKbcbXr0r6KczoFkU2I7EhogUSd0Oigykguw4Ia34Uc790m6Q1m3LVJd7lWFeZ0q64Uy8lqP-mlZuOgy7Sy~OKE7MZzlvRa6Yp5SUuMOF9iSHGeOIo4bIinQJZw0KuU1~XFSEdq9P1PYoH5eMoy2tH5x~g__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA|journal=Asian Journal on Energy and Environment|volume=6|issue=4|pages=214-231|issn=}}</ref> Heavy metals from these factors are predominantly present in water sources due to runoff where it is uptake by marine fauna and flora.<ref name=":6" />
+The mobility of certain metals including chromium (Cr) and uranium (U) varies depending on the oxidation state of the material.<ref>{{Cite book|url=https://enviro.wiki/images/c/c1/USEPA-2007-MNA_of_Inorganic_Contaminants_in_GW%2C_Vol_1_Technical_Basis_for_Assessment.pdf|title=Monitored natural attenuation of inorganic contaminants in groundwater, Volume 1 Technical basis for assessment|last=R.G. Ford, R.T. Wilkin, and R.W. Puls|publisher=U.S. Environmental Protection Agency, EPA/600/R-07/139|year=2007|oclc=191800707}}</ref> Microorganisms can be used to reduce the toxicity and mobility of chromium by reducing hexavalent chromium, Cr(VI) to trivalent Cr (III).<ref>{{Cite book|url=https://enviro.wiki/images/3/3a/USEPA-2007-MNA_of_Inorganic_Contaminants_in_GW%2C_Vol_2.pdf|title=Monitored Natural Attenuation of Inorganic Contaminants in Groundwater, Volume 2 - Assessment for Non-Radionulcides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium|last=R.G. Ford, R.T. Wilkin, and R.W. Puls|publisher=USEPA|year=2007}}</ref> Uranium can be reduced from the more mobile U(VI) oxidation state to the less mobile U(IV) oxidation state.<ref>{{cite journal|vauthors=Williams KH, Bargar JR, Lloyd JR, Lovley DR|date=June 2013|title=Bioremediation of uranium-contaminated groundwater: a systems approach to subsurface biogeochemistry|journal=Current Opinion in Biotechnology|volume=24|issue=3|pages=489–97|doi=10.1016/j.copbio.2012.10.008|pmid=23159488}}</ref><ref>{{Cite book|url=https://enviro.wiki/images/0/05/USEPA-2010-MNA_of_Inorganic_Contaminants_in_GW%2C_Vol_3.pdf|title=Monitored natural attenuation of inorganic contaminants in groundwater, Volume 3 Assessment for Radionuclides Including Tritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium|last=R.G. Ford and R.T. Wilkin|publisher=U.S. Environmental Protection Agency, EPA/600/R-10/093|year=2007}}</ref>  Microorganisms are used in this process because the reduction rate of these metals is often slow unless catalyzed by microbial interactions<ref name=":0">{{Cite book|title=Bioremediation of Metals and Radionuclides : What It Is and How It Works (2nd Edition).|last=Anna.|first=Hazen, Terry. Palmisano|date=2003|publisher=Lawrence Berkeley National Laboratory|oclc=316485842}}</ref>  Research is also underway to develop methods to remove metals from water by enhancing the sorption of the metal to cell walls.<ref name=":0" />  This approach has been evaluated for treatment of cadmium,<ref name="source 3">{{cite journal|vauthors=Ansari MI, Malik A|date=November 2007|title=Biosorption of nickel and cadmium by metal resistant bacterial isolates from agricultural soil irrigated with industrial wastewater|journal=Bioresource Technology|volume=98|issue=16|pages=3149–53|doi=10.1016/j.biortech.2006.10.008|pmid=17166714}}</ref> chromium,<ref name=":1">{{cite journal|vauthors=Durán U, Coronado-Apodaca KG, Meza-Escalante ER, Ulloa-Mercado G, Serrano D|date=May 2018|title=Two combined mechanisms responsible to hexavalent chromium removal on active anaerobic granular consortium|journal=Chemosphere|volume=198|pages=191–197|bibcode=2018Chmsp.198..191D|doi=10.1016/j.chemosphere.2018.01.024|pmid=29421729}}</ref> and lead.<ref name="source 1">{{cite journal|vauthors=Tripathi M, Munot HP, Shouche Y, Meyer JM, Goel R|date=May 2005|title=Isolation and functional characterization of siderophore-producing lead- and cadmium-resistant Pseudomonas putida KNP9|journal=Current Microbiology|volume=50|issue=5|pages=233–7|doi=10.1007/s00284-004-4459-4|pmid=15886913|s2cid=21061197}}</ref> [[Phytoextraction process]]es concentrate contaminants in the biomass for subsequent removal.
 == Limitations of bioremediation ==
-Bioremediation can be used to completely mineralize organic pollutants, to partially transform the pollutants, or alter their mobility.  [[Heavy metals]] and [[Agricultural pollution#Radioactive elements|radionuclides]] are elements that cannot be biodegraded, but can be bio-transformed to less mobile forms.<ref name="Disadv-Comprehensive">{{cite journal|last1=Juwarkar|first1=Asha A|last2=Singh|first2=Sanjeev K|last3=Mudhoo|first3=Ackmez|year=2010|title=A comprehensive overview of elements in bioremediation|journal=Reviews in Environmental Science and Bio/Technology|volume=9|issue=3|pages=215–88|name-list-style=vanc|doi=10.1007/s11157-010-9215-6|s2cid=85268562}}</ref><ref name="Disadv-Factors">{{cite journal |doi=10.1016/S0960-8524(99)00144-3 |title=Factors limiting bioremediation technologies |journal=Bioresource Technology |volume=74 |pages=63–7 |year=2000 |last1=Boopathy |first1=R }}</ref><ref name="Disadv-EncTox">{{cite book|title=Encyclopedia of toxicology|last1=Wexler|first1=editor-in-chief, Philip|date=2014|publisher=Academic Press Inc|isbn=9780123864543|edition=3rd|location=San Diego, Ca|page=489}}</ref> In some cases, microbes do not fully mineralize the pollutant, potentially producing a more toxic compound.<ref name="Disadv-EncTox" /> For example, under anaerobic conditions, the [[Reductive dechlorination|reductive dehalogenation]] of [[Trichloroethylene|TCE]] may produce [[Dichloroethene|dichloroethylene]] (DCE) and [[vinyl chloride]] (VC), which are suspected or known [[carcinogen]]s.<ref name="Disadv-Comprehensive" /> However, the microorganism ''[[Dehalococcoides]]'' can further reduce DCE and VC to the non-toxic product ethene.<ref>{{Cite journal|last1=Maymó-Gatell|first1=Xavier|last2=Chien|first2=Yueh-tyng|last3=Gossett|first3=James M.|last4=Zinder|first4=Stephen H.|date=1997-06-06|title=Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene|journal=Science|volume=276|issue=5318|pages=1568–1571|doi=10.1126/science.276.5318.1568|issn=0036-8075|pmid=9171062}}</ref>  Additional research is required to develop methods to ensure that the products from biodegradation are less persistent and less toxic than the original contaminant.<ref name="Disadv-EncTox" /> Thus, the metabolic and chemical pathways of the microorganisms of interest must be known.<ref name="Disadv-Comprehensive" /> In addition, knowing these pathways will help develop new technologies that can deal with sites that have uneven distributions of a mixture of contaminants.<ref name="Disadv-Overview">{{cite journal|last1=Vidali|first1=M.|year=2001|title=Bioremediation. An overview|url=https://www.iupac.org/publications/pac/pdf/2001/pdf/7307x1163.pdf|journal=Pure and Applied Chemistry|volume=73|issue=7|pages=1163–72|doi=10.1351/pac200173071163|s2cid=18507182}}</ref>
+Bioremediation can be used to completely mineralize organic pollutants, to partially transform the pollutants, or alter their mobility.  [[Heavy metals]] and [[Agricultural pollution#Radioactive elements|radionuclides]] are elements that cannot be biodegraded, but can be bio-transformed to less mobile forms.<ref name="Disadv-Comprehensive">{{cite journal|last1=Juwarkar|first1=Asha A|last2=Singh|first2=Sanjeev K|last3=Mudhoo|first3=Ackmez|year=2010|title=A comprehensive overview of elements in bioremediation|journal=Reviews in Environmental Science and Bio/Technology|volume=9|issue=3|pages=215–88|name-list-style=vanc|doi=10.1007/s11157-010-9215-6|s2cid=85268562}}</ref><ref name="Disadv-Factors">{{cite journal |doi=10.1016/S0960-8524(99)00144-3 |title=Factors limiting bioremediation technologies |journal=Bioresource Technology |volume=74 |pages=63–7 |year=2000 |last1=Boopathy |first1=R }}</ref><ref name="Disadv-EncTox">{{cite book|title=Encyclopedia of toxicology|last1=Wexler|first1=editor-in-chief, Philip|date=2014|publisher=Academic Press Inc|isbn=9780123864543|edition=3rd|location=San Diego, Ca|page=489}}</ref> In some cases, microbes do not fully mineralize the pollutant, potentially producing a more toxic compound.<ref name="Disadv-EncTox" /> For example, under anaerobic conditions, the [[Reductive dechlorination|reductive dehalogenation]] of [[Trichloroethylene|TCE]] may produce [[Dichloroethene|dichloroethylene]] (DCE) and [[vinyl chloride]] (VC), which are suspected or known [[carcinogen]]s.<ref name="Disadv-Comprehensive" /> However, the microorganism ''[[Dehalococcoides]]'' can further reduce DCE and VC to the non-toxic product ethene.<ref>{{Cite journal|last1=Maymó-Gatell|first1=Xavier|last2=Chien|first2=Yueh-tyng|last3=Gossett|first3=James M.|last4=Zinder|first4=Stephen H.|date=1997-06-06|title=Isolation of a Bacterium That Reductively Dechlorinates Tetrachloroethene to Ethene|journal=Science|volume=276|issue=5318|pages=1568–1571|doi=10.1126/science.276.5318.1568|issn=0036-8075|pmid=9171062}}</ref> Additional research is required to develop methods to ensure that the products from biodegradation are less persistent and less toxic than the original contaminant.<ref name="Disadv-EncTox" /> Thus, the metabolic and chemical pathways of the microorganisms of interest must be known.<ref name="Disadv-Comprehensive" /> In addition, knowing these pathways will help develop new technologies that can deal with sites that have uneven distributions of a mixture of contaminants.<ref name="Disadv-Overview">{{cite journal|last1=Vidali|first1=M.|year=2001|title=Bioremediation. An overview|url=https://www.iupac.org/publications/pac/pdf/2001/pdf/7307x1163.pdf|journal=Pure and Applied Chemistry|volume=73|issue=7|pages=1163–72|doi=10.1351/pac200173071163|s2cid=18507182}}</ref>
+Also, for biodegradation to occur, there must be a microbial population with the metabolic capacity to degrade the pollutant, an environment with the right growing conditions for the microbes, and the right amount of nutrients and contaminants.<ref name="Disadv-Overview" /><ref name="Disadv-Factors" /> The biological processes used by these microbes are highly specific, therefore, many environmental factors must be taken into account and regulated as well.<ref name="Disadv-Overview" /><ref name="Disadv-Comprehensive" /> Thus, bioremediation processes must be specifically made in accordance to the conditions at the contaminated site.<ref name="Disadv-Comprehensive" /> Also, because many factors are interdependent, small-scale tests are usually performed before carrying out the procedure at the contaminated site.<ref name="Disadv-Factors" /> However, it can be difficult to extrapolate the results from the small-scale test studies into big field operations.<ref name="Disadv-Overview" /> In many cases, bioremediation takes more time than other alternatives such as [[Landfill|land filling]] and [[incineration]].<ref name="Disadv-Overview" /><ref name="Disadv-Comprehensive" /> Another example is bioventing, this method is inexpensive to bioremediate contaminated sites, however this process is extensive and can take a few years to decontaminate a site.<ref>{{Cite journal|last=Sharma|first=Jot|date=2019|title=Advantages and Limitations of In Situ Methods of Bioremediation|url=https://rabm.scholasticahq.com/article/10941-advantages-and-limitations-of-in-situ-methods-of-bioremediation|journal=Recent Adv Biol Med|language=en|volume=5|issue=2019|pages=10941|doi=10.18639/RABM.2019.955923}}</ref>
+ In agricultural industries, the use of pesticides is a top factor in direct soil contamination and runoff water contamination. The limitation or remediation of pesticides is the low bioavailability.<ref name=":12">{{Cite journal|last=Odukkathil|first=Greeshma|last2=Vasudevan|first2=Namasivayam|date=2013|title=Toxicity and bioremediation of pesticides in agricultural soil|url=http://link.springer.com/10.1007/s11157-013-9320-4|journal=Reviews in Environmental Science and Bio/Technology|language=en|volume=12|issue=4|pages=421–444|doi=10.1007/s11157-013-9320-4|issn=1569-1705|via=}}</ref> Altering the pH and temperature of the contaminated soil is a resolution to increase bioavailability which, in turn, increased degradation of harmful compounds.<ref name=":12" /> The compound[[acrylonitrile]] is commonly produced in industrial setting but adversely contaminates soils. Microorganisms containing nitrile hydratases (NHase) degraded harmful acrylonitrile compounds into non-polluting substances.<ref>{{Cite journal|last=Supreetha|first=K.|last2=Rao|first2=Saroja Narsing|last3=Srividya|first3=D.|last4=Anil|first4=H. S.|last5=Kiran|first5=S.|date=2019|title=Advances in cloning, structural and bioremediation aspects of nitrile hydratases|url=https://doi.org/10.1007/s11033-019-04811-w|journal=Molecular Biology Reports|language=en|volume=46|issue=4|pages=4661–4673|doi=10.1007/s11033-019-04811-w|issn=1573-4978|via=}}</ref>
+Since the experience with harmful contaminants are limited, laboratory practices are required to evaluate effectiveness, treatment designs, and estimate treatment times.<ref name=":72">{{Cite journal|last=Sharma|first=Jot|date=2019|title=Advantages and Limitations of In Situ Methods of Bioremediation|url=https://rabm.scholasticahq.com/article/10941-advantages-and-limitations-of-in-situ-methods-of-bioremediation|journal=Recent Adv Biol Med|language=en|volume=5|issue=2019|pages=10941|doi=10.18639/RABM.2019.955923}}</ref> Bioremediation processes may take several months to several years depending on the size of the contaminated area.<ref>National Service Center for Environmental Publications (2012) A Citizen's Guide to Bioremediation. https://www.epa.gov/remedytech/citizens-guide-bioremediation#:~:text=The%20Citizen's%20Guide%20series%20is,up%20contaminated%20soil%20and%20groundwater.</ref>
-Also, for biodegradation to occur, there must be a microbial population with the metabolic capacity to degrade the pollutant, an environment with the right growing conditions for the microbes, and the right amount of nutrients and contaminants.<ref name="Disadv-Overview" /><ref name="Disadv-Factors" /> The biological processes used by these microbes are highly specific, therefore, many environmental factors must be taken into account and regulated as well.<ref name="Disadv-Overview" /><ref name="Disadv-Comprehensive" /> Thus, bioremediation processes must be specifically made in accordance to the conditions at the contaminated site.<ref name="Disadv-Comprehensive" />  Also, because many factors are interdependent, small-scale tests are usually performed before carrying out the procedure at the contaminated site.<ref name="Disadv-Factors" /> However, it can be difficult to extrapolate the results from the small-scale test studies into big field operations.<ref name="Disadv-Overview" /> In many cases, bioremediation takes more time than other alternatives such as [[Landfill|land filling]] and [[incineration]].<ref name="Disadv-Overview" /><ref name="Disadv-Comprehensive" />
 == Genetic engineering ==

v t e Pollution
History
Air	Acid rain Air quality index Atmospheric dispersion modeling Chlorofluorocarbon Combustion Biofuel Biomass Joss paper Open burning of waste Construction Renovation Demolition Exhaust gas Diesel exhaust Haze Smoke Indoor air quality Internal combustion engine Global dimming Global distillation Mining Ozone depletion Particulates Asbestos Metal working Oil refining Wood dust Welding Persistent organic pollutant Smelting Smog Soot Black carbon Volatile organic compound Waste
Biological	Biological hazard Genetic pollution Introduced species Invasive species
Digital	Information pollution
Electromagnetic	Light Ecological light pollution Overillumination Radio spectrum pollution
Natural	Ozone Radium and radon in the environment Volcanic ash Wildfire
Noise	Transportation Land Water Air Rail Sustainable transport Urban Sonar Marine mammals and sonar Industrial Military Abstract Noise control
Radiation	Actinides Bioremediation Nuclear fission Nuclear fallout Plutonium Poisoning Radioactivity Uranium Electromagnetic radiation and health Radioactive waste
Soil	Agricultural pollution Herbicides Manure waste Pesticides Land degradation Bioremediation Open defecation Electrical resistance heating Soil guideline values Phytoremediation
Solid waste	Advertising mail Biodegradable waste Brown waste Electronic waste Battery recycling Foam food container Food waste Green waste Hazardous waste Biomedical waste Chemical waste Construction waste Lead poisoning Mercury poisoning Toxic waste Industrial waste Lead smelting Litter Mining Coal mining Gold mining Surface mining Deep sea mining Mining waste Uranium mining Municipal solid waste Garbage Nanomaterials Plastic pollution Microplastics Packaging waste Post-consumer waste Waste management Landfill Thermal treatment
Space	Satellite
Visual	Air travel Clutter (advertising) Traffic signs Overhead power lines Vandalism
War	Chemical warfare Herbicidal warfare (Agent Orange) Nuclear holocaust (Nuclear fallout - nuclear famine - nuclear winter) Scorched earth Unexploded ordnance War and environmental law
Water	Agricultural wastewater Biological pollution Diseases Eutrophication Firewater Freshwater Groundwater Hypoxia Industrial wastewater Marine debris Monitoring Nonpoint source pollution Nutrient pollution Ocean acidification Oil exploitation Oil exploration Oil spill Pharmaceuticals Sewage Septic tanks Pit latrine Shipping Stagnation Sulfur water Surface runoff Thermal Turbidity Urban runoff Water quality
Topics	Pollutants Heavy metals Paint Brain health and pollution
Misc	Area source Debris Dust Garbology Legacy pollution Midden Point source Waste
Responses	Cleaner production Industrial ecology Pollution haven hypothesis Pollutant release and transfer register Polluter pays principle Pollution control Waste minimisation Zero waste
Lists	Diseases Law by country Most polluted cities Least polluted cities by PM_2.5 Most polluted countries Treaties
Categories (by country) Commons WikiProject Environment WikiProject Ecology Environment portal Ecology portal