Biological Processes at Elevated Temperatures

McNab and Narasimhan (1994) presented a framework that describes the reactions occurring in the fate and transport of the organic compounds in groundwater 

For dehalo-elimination reactions, it is helpful to simplify the reactions that are occurring as involving terminal electron acceptors (TEAs) and terminal electron donors (TEDs). This is also helpful, for in environmental remediation, there are two broad classes of organic compounds that are commonly dealt with (a) halogenated organic compounds (TEAs) and (b) fuels and residue from fuel production (TEDs). 

TEAs can be both natural and man-made. Natural TEAs include oxygen, nitrate, sulfate, ferric iron compounds, and manganese minerals such as pyrolusite (Mn02), carbohydrates, and carbon dioxide. In the biodegradation process, halogenated compounds can also be considered to be TEAs. 

TEDs include hydrogen, natural organic carbon, humic material, and nonhalo-genated fuel compounds. For reductive dehalogenation to occur, there must be both a TEA and a TED. For the biotic pathway, organisms must derive energy from the reaction. 

TABLE 24.5. Some Redox Processes That Consume Organic Matter and Reduce Inorganic Compounds in Groundwater 

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Several different processes have been proposed for the conversion of solid organic wastes to a more usable liquid or gaseous form to be utilized as fuel or petrochemical feedstocks. Principally the commonly discussed processes involve the biological conversion to alcohols, the catalytic chemical conversion to methanol or Fischer-Tropsch liquids via a carbon monoxide and hydrogen synthesis gas, or the thermochemical formation of gases or oxygenated liquids by pyrolysis. Pyrolysis is defined as the decomposition of organic material at elevated temperatures. The process to be described uses a very special case of pyrolysis. 

In water, PAHs may either evaporate, disperse into the water column, become incorporated into bottom sediments, concentrate in aquatic biota, or experience chemical oxidation and biodegradation. The most important degradation processes for PAHs in aquatic systems are photooxidation, chemical oxidation, and biological transformation by bacteria and animals. Most PAHs in aquatic environments are associated with particulate materials only about 33% are present in dissolved form. PAHs dissolved in the water column will probably degrade rapidly through photooxidation and degrade most rapidly at higher concentrations, at elevated temperatures, at... 

Both blocky and random poly(p-dioxanone-co-c-caprolactone) copol mers were prepared and extruded into monofilaments to study their physical and biological properties (Bezwada, Shalaby, and Erneta, 1991). Random copolymers were prepared by pol)Tnerizing the desired proportions of p-dioxanone and c-caprolactone in a single step process in the presence of an organometallic catah st and an initiator at elevated temperatures as described above for p-dioxanone. 

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