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Introduction

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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, 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, 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.

In-situ techniques

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Visual representation showing in-situ bioremediation. This process involves the addition of oxygen, nutrients, or microbes into contaminated soil to remove toxic pollutants.[2] Contamination includes buried waste and underground pipe leakage that infiltrate ground water systems.[9] The addition of oxygen removes the pollutants by producing carbon dioxide and water.[6]

Bioventing (formally Aerobic)

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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.[10] 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.[11] 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.

Biostimulation (formally Additives)

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Bioremediation can be carried out by bacteria that is naturally present in the environment or adding nutrients, this process is called biostimulation.[6]

Bacteria, also known as microbia, are naturally occurring in the environment and are used to degrade hydrocarbons.[13] 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.[14]

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.[15] At this site, microorganisms break down the carcinogenic compound trichloroethylene (TCE), which is a process seen in previous studies.[16]


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.[17] Nutrients are required for the biodegradation of oil pollution and can be used to reduce the negative output on the environment.[18] Specific to marine oil spills, nitrogen and phosphorus have been key nutrients in biodegradation.[19]

Bioattenuation

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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.[20] While there is no anthropogenic involvement in bioattenuation, the contaminated site must still be monitored.[20]

Biosparging

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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.[21] However, biosparging focuses on saturated contaminated zones, specifically related to ground water remediation.[22]

Ex-situ techniques

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Biopiles

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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.[23]

Windrows

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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.[24] The refinery has excavated approximately 115,000m3 of contaminated soil.[25]

Windrow systems are similar to compost techniques where soil is periodically turned in order to enhance aeration.[26] This periodic turning also allows contaminants present in the soil to be uniformly distributed which accelerates the process of bioremediation.[27]

Landfarming

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Landfarming, or land treatment, is a method commonly used for sludge spills. This method disperses contaminated soil and aerates the soil by cyclically rotating.[28] 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.[29]

Heavy metals

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Heavy metals become present in the environment due to anthropogenic activities or natural factors.[6] Anthropogenic activities include industrial emissions, electronic waste, and ore mining. Natural factors include mineral weathering, soil erosion and forest fires.[30] 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.[31] Heavy metals from these factors are predominantly present in water sources due to runoff where it is uptake by marine fauna and flora.[30]

Limitations of bioremediation

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Even though bioventing is an inexpensive method to bioremediate contaminated sites, this process is extensive and can take a few years to decontaminate a site.[32]


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.[33] Altering the pH and temperature of the contaminated soil is a resolution to increase bioavailability which, in turn, increased degradation of harmful compounds.[33]


Acrylonitrile is commonly produced in industrial setting but adversely contaminates soils. Microorganisms containing nitrile hydratases (NHase) degraded harmful acrylonitrile compounds into non-polluting substances.[34]

Since the experience with harmful contaminants are limited, laboratory practices are required to evaluate effectiveness, treatment designs, and estimate treatment times.[7] Bioremediation processes may take several months to several years depending on the size of the contaminated area.[35]

References

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  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)
  2. ^ 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.
  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.
  6. ^ a b c d 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. ^ a b 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
  10. ^ 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.
  11. ^ Norris, Robert (1993). Handbook of Bioremediation. CRC Press. p. 45. ISBN 9781351363457.
  12. ^ Norris, Robert (1993). Handbook of Bioremediation. CRC Press. p. 45. ISBN 9781351363457.
  13. ^ 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.
  14. ^ 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.
  15. ^ 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.
  16. ^ 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.
  17. ^ 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.
  18. ^ 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.
  19. ^ 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.
  20. ^ 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
  21. ^ Vidali, M (2001). "Bioremediation. An overview*". Pure and Applied Chemistry. 73 (7): 1163–1172.
  22. ^ 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.
  23. ^ 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.
  24. ^ 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.
  25. ^ 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.
  26. ^ 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.
  27. ^ 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)
  28. ^ 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
  29. ^ 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
  30. ^ 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.
  31. ^ 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.
  32. ^ 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.
  33. ^ 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.
  34. ^ 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.
  35. ^ 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.
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