Bioaugmentation

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Biological augmentation is the addition of archaea or bacterial cultures required to speed up the rate of degradation of a contaminant. [1] Organisms that originate from contaminated areas may already be able to break down waste, but perhaps inefficiently and slowly.

Contents

Bioaugmentation is a type of bioremediation in which it requires studying the indigenous varieties present in the location to determine if biostimulation is possible. After discovering the indigenous bacteria found in the location, if the indigenous bacteria can metabolize the contaminants, more of the indigenous bacterial cultures will be implemented into the location to boost the degradation of the contaminants. Bioaugmentation is the introduction of more archaea or bacterial cultures to enhance the contaminant degradation whereas biostimulation is the addition of nutritional supplements for the indigenous bacteria to promote the bacterial metabolism. If the indigenous variety do not have the metabolic capability to perform the remediation process, exogenous varieties with such sophisticated pathways are introduced. The utilization of bioaugmentation provides advancement in the fields of microbial ecology and biology, immobilization, and bioreactor design. [2]

Bioaugmentation is commonly used in municipal wastewater treatment to restart activated sludge bioreactors. Most cultures available contain microbial cultures, already containing all necessary microorganisms ( B. licheniformis , B. thuringiensis , P. polymyxa , B. stearothermophilus , Penicillium sp., Aspergillus sp., Flavobacterium , Arthrobacter , Pseudomonas , Streptomyces , Saccharomyces , etc.). Activated sludge systems are generally based on microorganisms like bacteria, protozoa, nematodes, rotifers, and fungi, which are capable of degrading biodegradable organic matter. There are many positive outcomes from the use of bioaugmentation, such as the improvement in efficiency and speed of the process of breaking down substances and the reduction of toxic particles in an area. [3]

Applications

Soil remediation

Bioaugmentation is favorable in contaminated soils that have undergone bioremediation, but still pose an environmental risk. This is because microorganisms that were originally in the environment did not accomplish their task during bioremediation when it came to breaking down chemicals in the contaminated soil. The failure of original bacteria can be caused by environmental stresses, as well as changes in the microbial population due to mutation rates. When microorganisms are added, they are potentially more suited to the nature of the new contaminant, meanwhile the older microorganisms are similar to the older pollution and contamination. [4] However, this is merely one of many factors; site size is also a very important determinant. In order to see whether bioaugmentation should be implemented, the overall setting must be considered. Also, some highly specialized microorganisms are not capable of adapting to certain site settings. Availability of certain microorganism types (as used for bioremediation) may also be a problem. Although bioaugmentation may appear to be a perfect solution for contaminated soil, it can have drawbacks. For example, the wrong type of bacteria can result in potentially clogged aquifers, or the remediation result may be incomplete or unsatisfactory. [4]

Bioaugmentation of chlorinated solvents

At sites where soil and groundwater are contaminated with chlorinated ethenes, such as tetrachloroethylene and trichloroethylene, bioaugmentation can be used to ensure that the in situ microorganisms can completely degrade these contaminants to ethylene and chloride, which are non-toxic. Bioaugmentation is typically only applicable to bioremediation of chlorinated ethenes, although there are emerging cultures with the potential to biodegrade other compounds including BTEX, chloroethanes, chloromethanes, and MTBE. The first reported application of bioaugmentation for chlorinated ethenes was at Kelly Air Force Base, TX. [5] Bioaugmentation is typically performed in conjunction with the addition of electron donor (biostimulation) to achieve geochemical conditions in groundwater that favor the growth of the dechlorinating microorganisms in the bioaugmentation culture.

Niche fitness

Including more microbes into an environment is beneficial to the speed of the cleanup duration. The interaction and competitions of two compounds influence the performance that a microorganism, original or new, could have. This can be tested by placing a soil that favors the new microbes into the area and then looking at the performance. The results will show if the new microorganism can perform well enough in that soil with other microorganisms. This helps to determine the correct amount of microbes and indigenous substances that are needed in order to optimize performance and create a co-metabolism. [4]

Coke plant wastewater in China

An example of how bioaugmentation has improved an environment, is in the coke plant wastewater in China. Coal in China is used as a main energy source and the contaminated water contains harmful toxic contaminants like ammonia, thiocyanate, phenols and other organic compounds, such as mono- and polycyclic nitrogen-containing aromatics, oxygen and sulfur-containing heterocyclics and polynuclear aromatic hydrocarbons. Previous measures to treat this problem was an aerobic-anoxic-oxic system, solvent extractions, stream stripping, and biological treatment. Bioaugmentation has been reported to remove 3-chlorobenzoate, 4-methyl benzoate, toluene, phenol, and chlorinated solvents.

The anaerobic reactor was packed with semi-soft media, which were constructed by plastic ring and synthetic fiber string. The anoxic reactor is a completely mixed reactor while the oxic reactor is a hybrid bioreactor in which polyurethane foam carriers were added. Water from anoxic reactor, odic reactor and sedimentation tank were used and had mix-ins of different amount of old and developed microbes with .75 concentration and 28 degree Celsius. The rate of contaminant degradation depended on the amount of microbe concentration. In the enhanced microbial community indigenous microorganisms broke down the contaminants in the coke plant wastewater, such as pyridines, and phenolic compounds. When indigenous heterotrophic microorganisms were added, they converted many large molecular compounds into smaller and simpler compounds, which could be taken from more biodegradable organic compounds. This proves that bioaugmentation could be used as a tool for the removal of unwanted compounds that are not properly removed by conventional biological treatment system. When bioaugmentation is combined with A1–A2–O system for the treatment of coke plant wastewater it is very powerful. [6]

Petroleum cleanup

In the petroleum industry, there is a large problem with how oilfield drilling pit is disposed of. Many used to simply place dirt over the pit, but it is far more productive and economically beneficial to use bioaugmentation. With the use of advanced microbes, drilling companies can actually treat the problem in the oilfield pit instead of transferring the waste around. Specifically, polycyclic aromatic hydrocarbons can be metabolized by some bacteria, which significantly reduces environmental damage from drilling activities. [7] Given suitable environmental conditions, microbes are placed in the oilpit to break down hydrocarbons and alongside are other nutrients. Before treatment there was a total petroleum hydrocarbon (TPH) level of 44,880 ppm, which within just 47 days the TPH was lowered to a level of 10,000 ppm to 6,486 ppm. [8]

Failures and potential solutions

There have been many instances where bioaugmentation had deficiencies in its process, including the use of the wrong organism. [9] The implementation of bioaugmentation on the environment can pose problems of predation, nutritional competition between indigenous and inoculated bacteria, insufficient inoculations, and disturbing the ecological balance due to large inoculations. [10] Each problem can be solved using different techniques to limit the possibilities of these problems occurring. Predation can be prevented by high initial doses of the inoculated bacteria or heat treatment prior to inoculation whereas nutritional competition can be settled with biostimulation. Insufficient inoculations can be treated by repeated or continual inoculations and large inoculations are resolved with highly monitored dosages of the bacteria.

Examples include the introduced bacteria fail to enhance the degradation within the soil, [11] and the bioaugmentation trials fail on the laboratory scale, but succeed on the large scale. [12] Many of these problems occurred because the microbial ecology issues were not taken into consideration in order to map the performance of the bioaugmentation. It is crucial to consider the microbes' ability to withstand the conditions in the microbial community to be placed in. In many of the cases that have failed, only the microbes' ability to break down compounds was considered and less their fitness in existing communities and the resulting competitive stress. [13] It is better to identify the existing communities before looking at the strains needed to break down pollutants. [14]


See also

Related Research Articles

Environmental remediation Removal of pollution from soil, groundwater etc.

Environmental remediation deals with the removal of pollution or contaminants from environmental media such as soil, groundwater, sediment, or surface water. Remedial action is generally subject to an array of regulatory requirements, and may also be based on assessments of human health and ecological risks where no legislative standards exist, or where standards are advisory.

Bioremediation 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 physiochemical treatment methods which suffer serious drawbacks, bioremediation is sustainable, eco-friendly, cheap, and scalable. Most bioremediation is inadvertent, involving native organisms. Research on bioremediation is heavily focused on stimulating the process by inoculation of a polluted site with organisms or supplying nutrients to promote the growth. In principle, bioremediation could be used to reduce the impact of byproducts created from anthropogenic activities, such as industrialization and agricultural processes. Bioremediation could prove less expensive and more sustainable than other remediation alternatives.

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.

Reductive dechlorination is Chemical reaction of chlorinated organic compounds with reductants. The reaction breaks C-Cl bonds, and releases chloride ions. Many modalities have been implemented, depending on the application. Reductive dechlorination is often applied to remediation of chlorinated pesticides or dry cleaning solvents. It is also used occasionally in the synthesis of organic compounds, e.g. as pharmaceuticals.

Phytoremediation 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.

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.

Mycoremediation 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.

Halorespiration or dehalorespiration or organohalide respiration is the use of halogenated compounds as terminal electron acceptors in anaerobic respiration. Halorespiration can play a part in microbial biodegradation. The most common substrates are chlorinated aliphatics, chlorinated phenols and chloroform. Dehalorespiring bacteria are highly diverse. This trait is found in some Campylobacterota, Thermodesulfobacteriota, Chloroflexota, low G+C gram positive Clostridia, and ultramicrobacteria.

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.

Biomining Technique of extracting metals from ores using prokaryotes or fungi

Biomining is the technique of extracting metals from ores and other solid materials typically using prokaryotes, fungi or plants. These organisms secrete different organic compounds that chelate metals from the environment and bring it back to the cell where they are typically used to coordinate electrons. It was discovered in the mid 1900s that microorganisms use metals in the cell. Some microbes can use stable metals such as iron, copper, zinc, and gold as well as unstable atoms such as uranium and thorium. Companies can now grow large chemostats of microbes that are leaching metals from their media, these vats of culture can then be transformed into many marketable metal compounds. Biomining is an environmentally friendly technique compared to typical mining. Mining releases many pollutants while the only chemicals released from biomining is any metabolites or gasses that the bacteria secrete. The same concept can be used for bioremediation models. Bacteria can be inoculated into environments contaminated with metals, oils, or other toxic compounds. The bacteria can clean the environment by absorbing these toxic compounds to create energy in the cell. Microbes can achieve things at a chemical level that could never be done by humans. Bacteria can mine for metals, clean oil spills, purify gold, and use radioactive elements for energy.

Phototrophic biofilm 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.

Many microorganisms can naturally grow together on surfaces to form complex aggregations called biofilms. Much research has been done on methods to remove biofilms in clinical and food manufacturing processes, but biofilms are also used for constructive purposes in a variety of industries. One distinctive characteristic of biofilm formation is that microorganisms within biofilms are often much tougher and more resistant to environmental stress compared to individual microorganisms. The cells are stationary and are able to adapt to adverse environments. This phenomenon of enhanced resistance can be beneficial in industrial chemical production where microorganisms within biofilms may tolerate higher chemical concentration and act as robust biorefineries for various products. These microbes have also been used in bioremediation to remove contaminants from freshwater and wastewater. More novel uses of biofilms include generating electricity using microbial fuel cells. Challenges to scaling up this technology include cost, controlling the growth of biofilms, and membrane fouling.

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.

A Bioelectrochemical reactor is a type of bioreactor where bioelectrochemical processes are used to degrade/produce organic materials using microorganisms. This bioreactor has two compartments: The anode, where the oxidation reaction takes place; And the cathode, where the reduction occurs. At these sites, electrons are passed to and from microbes to power reduction of protons, breakdown of organic waste, or other desired processes. They are used in microbial electrosynthesis, environmental remediation, and electrochemical energy conversion. Examples of bioelectrochemical reactors include microbial electrolysis cells, microbial fuel cells, enzymatic biofuel cells, electrolysis cells, microbial electrosynthesis cells, and biobatteries.

Biodegradable additives are additives that enhance the biodegradation of polymers by allowing microorganisms to utilize the carbon within the polymer chain as a source of energy. Biodegradable additives attract microorganisms to the polymer through quorum sensing after biofilm creation on the plastic product. Additives are generally in masterbatch formation that use carrier resins such as polyethylene (PE), polypropylene (PP), polystyrene (PS) or polyethylene terephthalate (PET).

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.

Bioremediation of radioactive waste

Bioremediation of radioactive waste or bioremediation of radionuclides is an application of bioremediation based on the use of biological agents bacteria, plants and fungi to catalyze chemical reactions that allow the decontamination of sites affected by radionuclides. These radioactive particles are by-products generated as a result of activities related to nuclear energy and constitute a pollution and a radiotoxicity problem due to its unstable nature of ionizing radiation emissions.

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.

<i>In situ</i> bioremediation

Bioremediation is the process of decontaminating polluted sites through the usage of either endogenous or external microorganism. In situ is a term utilized within a variety of fields meaning "on site" and refers to the location of an event. 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. 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. The most notable cases being the Deepwater Horizon oil spill in 2010 and the Exxon Valdez oil spill in 1989. 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 In situ bioremediation can further be categorized by the metabolism occurring, aerobic and anaerobic, and by the level of human involvement.

References

  1. ↑ Morganwalp, David W. "Scientists Discover Analog for Extraterrestrial Life in Idaho Hot Spring". toxics.usgs.gov. Retrieved 2015-09-11.
  2. ↑ Herrero, M; Stuckey, D.C. (2015). "Bioaugmentation and its application in wastewater treatment: A review". Chemosphere. 140: 119–128. Bibcode:2015Chmsp.140..119H. doi:10.1016/j.chemosphere.2014.10.033. hdl: 10044/1/19478 . PMID   25454204 – via Elsevier Science Direct.
  3. ↑ Huban, C.M. [Betz-Dearborn Inc., and R.D. [Sybron Chemicals Plowman, "Bioaugmentation: Put Microbes to Work.” Chemical Engineering 104.3", (1997): n. pag. Print.
  4. 1 2 3 Vogel, Timothy M. (1996). "Bioaugmentation as a soil bioremediation approach". Current Opinion in Biotechnology. 7 (3): 311–316. doi:10.1016/s0958-1669(96)80036-x. PMID   8785436.
  5. ↑ Major, D.W., M.L. McMaster, E.E. Cox, E.A. Edwards, S.M. Dworatzek, E.R. Hendrickson, M.G. Starr, J.A. Payne, and L.W. Buonamici (2002). "Field Demonstration of Successful Bioaugmentation to Achieve Dechlorination of Tetrachloroethene to Ethene". Environmental Science and Technology. 36 (23): 5106–5116. Bibcode:2002EnST...36.5106M. doi:10.1021/es0255711. PMID   12523427.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ↑ Jianlong Wang; et al. (2002). "Bioaugmentation as a tool to enhance the removal of refractory compound in coke plant wastewater". Process Biochemistry. 38 (5): 777–781. doi:10.1016/S0032-9592(02)00227-3.
  7. ↑ Fanelli, Alex (2016). "Bioaugmentation". Soil Bioremediation. Retrieved 26 December 2017.
  8. ↑ Barber, T. P., "Bioaugmentation for the treatment of oilfield drilling waste.", PennWell Conferences and Exhibitions, Houston, TX (United States), 1997
  9. ↑ Oerther DB, Danalewich J, Dulekgurgen E, Leveque E, Freedman D, Raskin L (1998). "Bioaugmentation of sequencing batch reactors for biological phosphorus removal: comparative rRNA sequence analysis and hybridization with oligonucleotide probes". Water Science and Technology. 37 (4–5): 469–473. doi: 10.1016/S0273-1223(98)00148-6 .
  10. ↑ Raper, E; Stephenson, T; Anderson, D.R. (2018). "Industrial Wastewater Treatment through Bioaugmentation". Process Safety and Environmental Protection. 118: 178–187. doi:10.1016/j.psep.2018.06.035 – via Elsevier Science Direct.
  11. ↑ Goldstein RM, Mallory LM, Alexander M (1985). "Reasons for possible failure of inoculation to enhance biodegradation". Appl Environ Microbiol. 50 (4): 977–83. doi:10.1128/AEM.50.4.977-983.1985. PMC   291779 . PMID   4083891.
  12. ↑ Stephenson D, Stephenson T (1992). "Bioaugmentation for enhancing biological wastewater treatment". Biotechnol. Adv. 10 (4): 549–59. doi:10.1016/0734-9750(92)91452-k. PMID   14543705.
  13. ↑ Smith RC, Saikaly PE, Zhang K, Thomas S, Oerther DB (2008). "Ecological engineering of bioaugmentation from side-stream nitrification". Water Science and Technology. 57 (12): 1927–1933. doi: 10.1016/S0273-1223(98)00148-6 . PMID   18587180.
  14. ↑ Thompson Ian P.; et al. (2005). "Bioaugmentation for bioremediation: the challenge of strain selection". Environmental Microbiology. 7 (7): 909–915. doi: 10.1111/j.1462-2920.2005.00804.x . PMID   15946288.
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