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Cometabolic Aerobic and Anaerobic Oxidation
Cometabloic oxidation, aerobic and anaerobic, is essentially the same thing as direct aerobic and anaerobic respiration except for the fact that the organism doing the oxidation does not gain energy and cannot grow from the oxidized products after the process, in contrary to Direct. There is one major difference between "regular" and Cometabolic Oxidation. The major difference in the two are that in Cometabolic oxidation when the CAHs (Chlorinated aliphatic hydrocarbons) accept an electron from oxygen, There is less chlorine to work with in the environment so then there is less energy to use. This results in different products such as, carbon dioxide, water, and escaped energy based on thermodynamics. There is no Chlorine as a product based on the lack there of, prior to the redox reaction. In Cometabolic Anaerobic Oxidation, as Cometabolic Aerobic Oxidation, there is no growth to the cell when being chlorinated. When naturally occurring it is nearly indistinguishable, as the products are so similar. In a lab controlled environment the two can be distinguished from one another. (Environmental Protection Agency. July 2010.)''' '''

Major Events using Bioremediation
Bioremediation has been used in lots of major events in our history. In 1986, The chernobyl nuclear disaster was too extreme for bioremediation to be positively effected by it. Mass amounts of bioremediation treatment was used to help control and reduce the effects of the Exxon Valdez oil spill in 1989 and BP’s Deepwater Horizon oil spill in 2010. More common and everyday uses include things such as composting. Bioremediation is such an effective tool in degrading pollutants that it has been used in over 100 superfund sites in America alone.

Additives
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.

Many biological processes are sensitive to pH and function most efficiently in near neutral conditions. The pH level affects the different aspects of bioremediation such as; the solubility of the nutrients and other additives that the microorganisms need to grow and break down pollutants which ultimately slow the process of doing so. 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. The optimal pH level for Microorganisms is about 6-8 on the pH scale.

Limitations
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. In some cases, microbes do not fully mineralize the pollutant, potentially producing a more toxic compound. For example, under anaerobic conditions, the reductive dehalogenation of TCE may produce dichloroethylene (DCE) and vinyl chloride (VC), which are suspected or known carcinogens. However, the microorganism Dehalococcoides can further reduce DCE and VC to the non-toxic product ethene. Additional research is required to develop methods to ensure that the products from biodegradation are less persistent and less toxic than the original contaminant. When microorganisms degrade contaminants, it is important to account for the concentration of the contaminants and the contaminant bioavailability, meaning how much of the contaminants is biodegraded, which is dependent on the concentration of the contaminants itself. Thus, the metabolic and chemical pathways of the microorganisms of interest must be known. In addition, knowing these pathways will help develop new technologies that can deal with sites that have uneven distributions of a mixture of contaminants.

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. The biological processes used by these microbes are highly specific, therefore, many environmental factors, such as; temperature, pH, water content, nutrient availability, and redox potential must be taken into account and regulated as well. Thus, bioremediation processes must be specifically made in accordance to the conditions at the contaminated site. Also, because many factors are interdependent, small-scale tests are usually performed before carrying out the procedure at the contaminated site. However, it can be difficult to extrapolate the results from the small-scale test studies into big field operations as in such a large scale it is hard to control so many variables and keep them optimal so that biodegradation can be fully effective. In many cases, bioremediation takes more time than other alternatives such as land filling and incineration.