Bioaugmentation

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 in a contaminated areas may be already able to break down waste, but ineffeciently and slowly.

Bioaugmentation usually requires studying the indigenous varieties present in the location to determine if biostimulation is possible. If the indigenous variety do not have the metabolic capability to perform the remediation process, exogenous varieties with such sophisticated pathways are introduced.

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, Triphoderma, etc.). Whereas activated sludge systems are generally based on microorganisms like bacteria, protozoa, nematodes, rotifers and fungi capable to degrade biodegradable organic matter. There are many positive outcomes from the use of bioaugmentation like the improvement in efficiency and speed of the process of breaking down substances and the reduction of toxic particles inhibiting an area. [2]

Soil remediation

Bioaugmentation is favored in a contaminated area 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. A potential reason for this can be due to 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. 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. And, availability of certain microorganism types (as used for bioremediation) may also be a problem. Although bioaugmentation may appear to be a perfect solution to contaminated soil, it can have its drawbacks. For example, the wrong type of bacteria can result in potentially clogged aquifers, or the remediation result may be incomplete or unsatisfactory. [3]

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.[4] 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. 'Bioaugmentation Cultures.[3]

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.[5]

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. 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.[6] For restoration of oil-field drill-cuttings contaminated with polycyclic aromatic hydrocarbons (PAH), Bacillus subtilis and Pseudomonas aeruginosa are capable of reducing the PAH below detection limits.[7]

Failures and potential solutions

There have been many instances where bioaugmentation had deficiencies in its process. Examples include Goldstein et al., 1985;[8] Stephenson and Stephenson, 1992;[9] Bouchez et al., 2000; Vogel and Walter, 2001; Wagner-Döbler, 2003. 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. It is better to identify the existing communities before looking at the strains needed to break down pollutants.[10]


See also

References

  1. ↑ Morganwalp, David W. "Scientists Discover Analog for Extraterrestrial Life in Idaho Hot Spring". toxics.usgs.gov. Retrieved 2015-09-11.
  2. ↑ 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.
  3. 1 2 Vogel, Timothy M. (1996). "Bioaugmentation as a soil bioremediation approach". Current Opinion in Biotechnology. 7 (3): 311–316. PMID 8785436.
  4. ↑ 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: 5106–5116. doi:10.1021/es0255711.
  5. ↑ Jianlong, Wang, et al., "Bioaugmentation as a tool to enhance the removal of refractory compound in coke plant wastewater", Process Biochemistry 38.5, (2002): 777-781.
  6. ↑ Barber, T. P., "Bioaugmentation for the treatment of oilfield drilling waste.", PennWell Conferences and Exhibitions, Houston, TX (United States), 1997
  7. ↑ Reuben N. Okparanma, Josiah M. Ayotamuno and Peremelade P. Araka (2009). "Bioremediation of hydrocarbon contaminated-oil field drill-cuttings with bacterial isolates". African Journal of Environmental Science and Technology. 3 (5): 131–140. doi:10.5897/AJEST09.046.
  8. ↑ Goldstein RM, Mallory LM, Alexander M. (1985). "Reasons for possible failure of inoculation to enhance biodegradation". Appl Environ Microbiol. 50 (4): 977–83. PMID 4083891.
  9. ↑ Stephenson D, Stephenson T. (1992). "Bioaugmentation for enhancing biological wastewater treatment". Biotechnol Adv. 10 (4): 549–59. PMID 14543705.
  10. ↑ Thompson, Ian P., et al., "Bioaugmentation for bioremediation: the challenge of strain selection.", Environmental Microbiology 7.7, (2005): 909-915.

Sources

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