In situ bioremediation

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In Situ Bioremediation In Situ Bioremediation.png
In Situ Bioremediation

Bioremediation is the process of decontaminating polluted sites through the usage of either endogenous or external microorganism. [1] In situ is a term utilized within a variety of fields meaning "on site" and refers to the location of an event. [2] Within the context of bioremediation, in situ indicates that the location of the bioremediation has occurred at the site of contamination without the translocation of the polluted materials. Bioremediation is used to neutralize pollutants including Hydrocarbons, chlorinated compounds, nitrates, toxic metals and other pollutants through a variety of chemical mechanisms. [1] Microorganism used in the process of bioremediation can either be implanted or cultivated within the site through the application of fertilizers and other nutrients. Common polluted sites targeted by bioremediation are groundwater/aquifers and polluted soils. Aquatic ecosystems affected by oil spills have also shown improvement through the application of bioremediation. [3] The most notable cases being the Deepwater Horizon oil spill in 2010 [4] and the Exxon Valdez oil spill in 1989. [5] Two variations of bioremediation exist defined by the location where the process occurs. Ex situ bioremediation occurs at a location separate from the contaminated site and involves the translocation of the contaminated material. In situ occurs within the site of contamination [1] In situ bioremediation can further be categorized by the metabolism occurring, aerobic and anaerobic, and by the level of human involvement.

Contents

History

The Sun Oil pipeline spill in Ambler, Pennsylvania spurred the first commercial usage of in situ bioremediation in 1972 to remove hydrocarbons from contaminated sites. [6] A patent was filed in 1974 by Richard Raymond, Reclamation of Hydrocarbon Contaminated Ground Waters, which provided the basis for the commercialization of in situ bioremediation. [6]

Classifications of In situ Bioremediation

Accelerated

Accelerated in situ bioremediation is defined when a specified microorganism is targeted for growth through the application of either nutrients or an electron donor to the contaminated site. Within aerobic metabolism the nutrient added to the soil can be solely Oxygen. Anaerobic in situ bioremediation often requires a variety of electron donors or acceptors such as benzoate and lactate. [7] Besides nutrients, microorganisms can also be introduced directly to the site within accelerated in situ bioremediation. [8] The addition of extraneous microorganisms to a site is termed bioaugmentation and is used when a particular microorganism is effective at degrading the pollutant at the site and is not found either naturally or at a high enough population to be effective. [7] Accelerated in situ bioremediation is utilized when the desired population of microorganisms within a site is not naturally present at a sufficient level to effectively degrade the pollutants. It also is used when the required nutrients within the site are either not at a concentration sufficient to support growth or are unavailable. [7]

Raymond Process

The Raymond Process is a type of accelerated in situ bioremediation that was developed by Richard Raymond and involves the introduction of nutrients and electron acceptors to a contaminated site. [9] This process is primarily used to treat polluted groundwater. In the Raymond process a loop system is created. Contaminated Groundwater from downstream of the groundwater flow is pumped to the surface and infused with nutrients and an electron donor, often oxygen. This treated water is then pumped back down below the water table upstream of where it was originally taken. This process introduces nutrients and electron donors into the site allowing for the growth of a determined microbial population. [9]

Oxygen Injection

In contaminated sites where the desired microbial metabolism is aerobic the introduction of oxygen to the site can be used to increase the population of targeted microorganisms. [10] The injection of Oxygen can occur through a variety of processes. Oxygen can be injected into the subsurface through injection wells. It can also be introduced through an injection gallery. The presence of oxygen within a site is often the limiting factor when determining the time frame and efficacy of a proposed in situ bioremediation process.

Ozone Injection

Ozone injected into the subsurface can also be a means of introducing oxygen into a contaminated site. [10] Despite being a strong oxidizing agent and potentially having a toxic effect on subsurface microbial populations, ozone can be an efficient means of spreading oxygen throughout a site due to its high solubility. [10] Within twenty minutes after being injected into the subsurface, fifty percent of the ozone will have decomposed to Oxygen. [10] Ozone is commonly introduced to the soil in either a dissolved or gaseous state. [10]

Accelerated Anaerobic In situ Bioremediation

Within accelerated anaerobic in situ bioremediation electron donors and acceptors are introduced into a contaminated site in order to increase the population of anaerobic microorganisms. [9]

Monitored Natural Attenuation (MNA)

Monitored Natural Attenuation is in situ bioremediation that occurs with little to no human intervention. [11] This process relies on the natural microbial populations sustained within the contaminated sites to over time reduce the contaminants to a desired level. [11] During monitored natural attenuation the site is monitored in order to track the progress of the bioremediation. [11] Monitored natural attenuation is used in sites where the source of contamination is no longer present, often after other more active types of in situ bioremediation have been conducted. [11]

Uses of In situ bioremediation

Hydrocarbon Degradation

Naturally occurring within the soil are microbial populations that utilize hydrocarbons as a source of energy and carbon. [9] Upwards to twenty percent of microbial soil populations have the ability to metabolize hydrocarbons. [9] These populations can through either accelerated or natural monitored attenuation be utilized to neutralize within the soil hydrocarbon pollutants. The metabolic mode of hydrocarbon remediation is primarily aerobic. [9] The end products of the remediation for hydrocarbons are Carbon Dioxide and water. [9] Hydrocarbons vary in ease of degradation based on their structure. Long chain aliphatic carbons are the most effectively degraded. Short chained, branched, and quaternary aliphatic hydrocarbons are less effectively degraded. [9] Alkene degradation is dependent on the saturation of the chain with saturated alkenes being more readily degraded. [9] Large numbers of microbes with the ability to metabolize aromatic hydrocarbons are present within the soil. Aromatic hydrocarbons are also susceptible to being degraded through anaerobic metabolism. [9] Hydrocarbon metabolism is an important facet of in situ bioremediation due to the severity of petroleum spills around the world. Polynuclear aromatic carbons susceptibility to degradation is related to the number of aromatic rings within the compound. [9] Compounds with two or three rings are degraded at an effective rate, but compounds possessing four or more rings can be more resilient to bioremediation efforts. [9] Degradation of polynuclear aromatic carbons with less than four rings is accomplished by various aerobic microbes present in the soil. Meanwhile, for larger-molecular-sized compounds, the only metabolic mode that has shown to be effective is cometabolism. [9] The fungus genus Phanerochaete under anaerobic conditions has species with the ability to metabolize some polynuclear aromatic carbons utilizing a peroxidase enzyme. [9] [12]

Chlorinated Compounds

Chlorinated Aliphatic Compounds

A variety of metabolic modes exist capable of degrading chlorinated aliphatic compounds. Anaerobic reduction, oxidation of the compound, and cometabolism under aerobic conditions are the three main metabolic modes utilized by microorganisms to degrade chlorinated aliphatic compounds. [9] Organisms that can readily metabolize chlorinated aliphatic compounds are not common in the environment. [9] One and two carbons that have little chlorination are the compounds most effectively metabolized by soil microbial populations. [9] The degradation of chlorinated aliphatic compounds is most often performed through cometabolism. [9]

Synthesis and general structure of polychlorinated byphenyls. Reacciotriclorur.png
Synthesis and general structure of polychlorinated byphenyls.

Chlorinated Aromatic Hydrocarbons

Chlorinated aromatic hydrocarbons are resistant to bioremediation and many microorganisms lack the ability to degrade the compounds. Chlorinated aromatic hydrocarbons are most often degraded through a process of reductive dechlorination under anaerobic conditions. [9] Polychlorinated biphenyls (PCBs) are primarily degraded through cometabolism. There are also some fungi that can degrade these compounds as well. Studies show an increase in PCB degradation when biphenyl is added to the site due to cometabolic effects that the enzymes used to degrade biphenyl have on PCBs. [9]

Benefits

Due to in situ bioremediation taking place at the site of contamination there is a lessened risk of cross contamination as opposed to ex situ bioremediation where the polluted material is transported to other sites. In situ bioremediation can also have lower costs and a higher rate of decontamination than ex situ bioremediation.

Related Research Articles

<span class="mw-page-title-main">Hydrocarbon</span> Organic compound consisting entirely of hydrogen and carbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may be similar to that of gasoline or lighter fluid. They occur in a diverse range of molecular structures and phases: they can be gases, liquids, low melting solids or polymers.

<span class="mw-page-title-main">Environmental remediation</span> Removal of pollution from soil, groundwater etc.

Environmental remediation is the cleanup of hazardous substances dealing with the removal, treatment and containment of pollution or contaminants from environmental media such as soil, groundwater, sediment. Remediation may be required by regulations before development of land revitalization projects. Developers who agree to voluntary cleanup may be offered incentives under state or municipal programs like New York State's Brownfield Cleanup Program. If remediation is done by removal the waste materials are simply transported off-site for disposal at another location. The waste material can also be contained by physical barriers like slurry walls. The use of slurry walls is well-established in the construction industry. The application of (low) pressure grouting, used to mitigate soil liquefaction risks in San Francisco and other earthquake zones, has achieved mixed results in field tests to create barriers, and site-specific results depend upon many variable conditions that can greatly impact outcomes.

<span class="mw-page-title-main">Bioremediation</span> Process used to treat contaminated media such as water and soil

Bioremediation broadly refers to any process wherein a biological system, living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluents etc., in natural or artificial settings. The natural ability of organisms to adsorb, accumulate, and degrade common and emerging pollutants has attracted the use of biological resources in treatment of contaminated environment. In comparison to conventional physicochemical treatment methods bioremediation may offer considerable advantages as it aims to be sustainable, eco-friendly, cheap, and scalable.

Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain.

<span class="mw-page-title-main">Phytoremediation</span> Decontamination technique using living plants

Phytoremediation technologies use living plants to clean up soil, air and water contaminated with hazardous contaminants. It is defined as "the use of green plants and the associated microorganisms, along with proper soil amendments and agronomic techniques to either contain, remove or render toxic environmental contaminants harmless". The term is an amalgam of the Greek phyto (plant) and Latin remedium. Although attractive for its cost, phytoremediation has not been demonstrated to redress any significant environmental challenge to the extent that contaminated space has been reclaimed.

Biological augmentation is the addition of archaea or bacterial cultures required to speed up the rate of degradation of a contaminant. Organisms that originate from contaminated areas may already be able to break down waste, but perhaps inefficiently and slowly.

Biostimulation involves the modification of the environment to stimulate existing bacteria capable of bioremediation. This can be done by addition of various forms of rate limiting nutrients and electron acceptors, such as phosphorus, nitrogen, oxygen, or carbon. Alternatively, remediation of halogenated contaminants in anaerobic environments may be stimulated by adding electron donors, thus allowing indigenous microorganisms to use the halogenated contaminants as electron acceptors. EPA Anaerobic Bioremediation Technologies Additives are usually added to the subsurface through injection wells, although injection well technology for biostimulation purposes is still emerging. Removal of the contaminated material is also an option, albeit an expensive one. Biostimulation can be enhanced by bioaugmentation. This process, overall, is referred to as bioremediation and is an EPA-approved method for reversing the presence of oil or gas spills. While biostimulation is usually associated with remediation of hydrocarbon or high production volume chemical spills, it is also potentially useful for treatment of less frequently encountered contaminant spills, such as pesticides, particularly herbicides.

<span class="mw-page-title-main">Mycoremediation</span> Process of using fungi to degrade or sequester contaminants in the environment

Mycoremediation is a form of bioremediation in which fungi-based remediation methods are used to decontaminate the environment. Fungi have been proven to be a cheap, effective and environmentally sound way for removing a wide array of contaminants from damaged environments or wastewater. These contaminants include heavy metals, organic pollutants, textile dyes, leather tanning chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbons, pharmaceuticals and personal care products, pesticides and herbicides in land, fresh water, and marine environments.

Cometabolism is defined as the simultaneous degradation of two compounds, in which the degradation of the second compound depends on the presence of the first compound. This is in contrast to simultaneous catabolism, where each substrate is catabolized concomitantly by different enzymes. Cometabolism occurs when an enzyme produced by an organism to catalyze the degradation of its growth-substrate to derive energy and carbon from it is also capable of degrading additional compounds. The fortuitous degradation of these additional compounds does not support the growth of the bacteria, and some of these compounds can even be toxic in certain concentrations to the bacteria.

Organohalide respiration (OHR) (previously named halorespiration or dehalorespiration) is the use of halogenated compounds as terminal electron acceptors in anaerobic respiration. Organohalide respiration can play a part in microbial biodegradation. The most common substrates are chlorinated aliphatics (PCE, TCE, chloroform) and chlorinated phenols. Organohalide-respiring bacteria are highly diverse. This trait is found in some Campylobacterota, Thermodesulfobacteriota, Chloroflexota (green nonsulfur bacteria), low G+C gram positive Clostridia, and ultramicrobacteria.

Richard Bartha is an American microbiologist. He is best known professionally for his seminal discoveries in the field of bacterial pollution control ("bioremediation").

Dehalococcoides is a genus of bacteria within class Dehalococcoidia that obtain energy via the oxidation of hydrogen and subsequent reductive dehalogenation of halogenated organic compounds in a mode of anaerobic respiration called organohalide respiration. They are well known for their great potential to remediate halogenated ethenes and aromatics. They are the only bacteria known to transform highly chlorinated dioxins, PCBs. In addition, they are the only known bacteria to transform tetrachloroethene to ethene.

Microbial biodegradation is the use of bioremediation and biotransformation methods to harness the naturally occurring ability of microbial xenobiotic metabolism to degrade, transform or accumulate environmental pollutants, including hydrocarbons, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), heterocyclic compounds, pharmaceutical substances, radionuclides and metals.

<span class="mw-page-title-main">Phototrophic biofilm</span> Microbial communities including microorganisms which use light as their energy source

Phototrophic biofilms are microbial communities generally comprising both phototrophic microorganisms, which use light as their energy source, and chemoheterotrophs. Thick laminated multilayered phototrophic biofilms are usually referred to as microbial mats or phototrophic mats. These organisms, which can be prokaryotic or eukaryotic organisms like bacteria, cyanobacteria, fungi, and microalgae, make up diverse microbial communities that are affixed in a mucous matrix, or film. These biofilms occur on contact surfaces in a range of terrestrial and aquatic environments. The formation of biofilms is a complex process and is dependent upon the availability of light as well as the relationships between the microorganisms. Biofilms serve a variety of roles in aquatic, terrestrial, and extreme environments; these roles include functions which are both beneficial and detrimental to the environment. In addition to these natural roles, phototrophic biofilms have also been adapted for applications such as crop production and protection, bioremediation, and wastewater treatment.

Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the subsurface. Globally, between 25 per cent and 40 per cent of the world's drinking water is drawn from boreholes and dug wells. Groundwater is also used by farmers to irrigate crops and by industries to produce everyday goods. Most groundwater is clean, but groundwater can become polluted, or contaminated as a result of human activities or as a result of natural conditions.

Petroleum microbiology is a branch of microbiology that deals with the study of microorganisms that can metabolize or alter crude or refined petroleum products. These microorganisms, also called hydrocarbonoclastic microorganisms, can degrade hydrocarbons and, include a wide distribution of bacteria, methanogenic archaea, and some fungi. Not all hydrocarbonoclasic microbes depend on hydrocarbons to survive, but instead may use petroleum products as alternative carbon and energy sources. Interest in this field is growing due to the increasing use of bioremediation of oil spills.

Adsorbable organic halides (AOX) is a measure of the organic halogen load at a sampling site such as soil from a land fill, water, or sewage waste. The procedure measures chlorine, bromine, and iodine as equivalent halogens, but does not measure fluorine levels in the sample.

Bioremediation of petroleum contaminated environments is a process in which the biological pathways within microorganisms or plants are used to degrade or sequester toxic hydrocarbons, heavy metals, and other volatile organic compounds found within fossil fuels. Oil spills happen frequently at varying degrees along with all aspects of the petroleum supply chain, presenting a complex array of issues for both environmental and public health. While traditional cleanup methods such as chemical or manual containment and removal often result in rapid results, bioremediation is less labor-intensive, expensive, and averts chemical or mechanical damage. The efficiency and effectiveness of bioremediation efforts are based on maintaining ideal conditions, such as pH, RED-OX potential, temperature, moisture, oxygen abundance, nutrient availability, soil composition, and pollutant structure, for the desired organism or biological pathway to facilitate reactions. Three main types of bioremediation used for petroleum spills include microbial remediation, phytoremediation, and mycoremediation. Bioremediation has been implemented in various notable oil spills including the 1989 Exxon Valdez incident where the application of fertilizer on affected shoreline increased rates of biodegradation.

Polychorinated biphenyls, or PCBs, are a type of chemical that was widely used in the 1960s and 1970s, and which are a contamination source of soil and water. They are fairly stable and therefore persistent in the environment. Bioremediation of PCBs is the use of microorganisms to degrade PCBs from contaminated sites, relying on multiple microorganisms' co-metabolism. Anaerobic microorganisms dechlorinate PCBs first, and other microorganisms that are capable of doing BH pathway can break down the dechlorinated PCBs to usable intermediates like acyl-CoA or carbon dioxide. If no BH pathway-capable microorganisms are present, dechlorinated PCBs can be mineralized with help of fungi and plants. However, there are multiple limiting factors for this co-metabolism.

Hydrocarbonoclastic bacteria are a heterogeneous group of prokaryotes which can degrade and utilize hydrocarbon compounds as source of carbon and energy. Despite being present in most of environments around the world, several of these specialized bacteria live in the sea and have been isolated from polluted seawater.

References

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  2. ↑ "Charlton T. Lewis, Charles Short, A Latin Dictionary, sĭtus". www.perseus.tufts.edu. Retrieved 4 April 2017.
  3. ↑ Perelo, Louisa Wessels (15 May 2010). "Review: In situ and bioremediation of organic pollutants in aquatic sediments". Journal of Hazardous Materials. 177 (1–3): 81–89. doi:10.1016/j.jhazmat.2009.12.090. PMID   20138425.
  4. ↑ Biello, David. "Slick Solution: How Microbes Will Clean Up the Deepwater Horizon Oil Spill". Scientific American. Retrieved 17 March 2017.
  5. ↑ Atlas, Ronald M.; Hazen, Terry C. (15 August 2011). "Oil Biodegradation and Bioremediation: A Tale of the Two Worst Spills in U.S. History". Environmental Science & Technology. 45 (16): 6709–6715. Bibcode:2011EnST...45.6709A. doi:10.1021/es2013227. ISSN   0013-936X. PMC   3155281 . PMID   21699212.
  6. 1 2 "Lecture 12 Bioremediation" (PDF). Online Course Work Massachusetts Institute of Technology. Retrieved 17 March 2017.
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  8. ↑ Ellis, David E.; Lutz, Edward J.; Odom, J. Martin; Buchanan, Ronald J.; Bartlett, Craig L.; Lee, Michael D.; Harkness, Mark R.; DeWeerd, Kim A. (1 June 2000). "Bioaugmentation for Accelerated In Situ Anaerobic Bioremediation". Environmental Science & Technology. 34 (11): 2254–2260. Bibcode:2000EnST...34.2254E. doi:10.1021/es990638e. ISSN   0013-936X.
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  12. ↑ Syed, Khajamohiddin; Yadav, Jagjit S. (1 November 2012). "P450 monooxygenases (P450ome) of the model white rot fungus Phanerochaete chrysosporium". Critical Reviews in Microbiology. 38 (4): 339–363. doi:10.3109/1040841X.2012.682050. ISSN   1040-841X. PMC   3567848 . PMID   22624627.
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