Degradation, microbiological

Goldstein etal. (1961) exposed acetylated ponderosa pine for 12 weeks to six basidio-mycete fungi, according to ASTM D1413-56T, with a WPG of 18 % reported to be sufficient to provide decay resistance. Peterson and Thomas (1978) acetylated loblolly pine (Pinus taeda), green ash (Fraxinus americana) and yellow poplar Liriodendron tulipfera), also 

Fungus (brown rot) Wood species Threshold [WPG (%)] Virulence (%) Reference 

Coniophora puteana (BAM 15) Beech (Tagus sylvatica) 17 27 Beckers eta/. (1 994) 

Coniophora puteana (FPRL 11 F) Corsican pine (Pinus nigra) 24 58 Forster eta/. (1997) 

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Many tracer chemicals are inherently unstable even as the unlabeled forms. Susceptibility of a chemical to hydrolysis, oxidation, photolysis, and microbiological degradation needs to be evaluated when designing suitable storage conditions for the labeled compound. Eactors that reduce radiolytic degradation, such as dispersal in solution, are apt to increase chemical degradation or instability. 

Since the microbiological degradation is a rather specialized reaction, no experimental details are given in this chapter. The success of such a reaction depends not only on the proper choice of substrate and proper duplication of the fermentation medium, but also on obtaining the proper strain of microorganism reported to perform a particular transformation. 

BSI recommends in the table of water treatment for hot water systems that chromate inhibitors should not be used because of their undesirable impact on the environment. It should also be noted that some treatment chemicals are microbiologically degraded in storage. 

It is not usual for unopened drums of nitrite-based chemical to degrade, and the product should remain in good condition for several years. However, it is possible for tannin-based corrosion inhibitors to degrade, even in unopened drums. Under warm conditions (such as storage in a boil-erhouse) and in the absence of a small amount of suitable microbiocide in the formulation, plastic drums containing tannin products may swell considerably because of microbiological degradation and gas formation. Care is needed to avoid accidents. 

Possible exposure to pesticide-derived N,-nitroso compounds depends on environmental processes that influence formation, movement, and degradation of the compounds. Although laboratory studies have shown the feasibility of environmental nitrosamine formation, there has been little evidence that it is an important process. Nitrosamines vary greatly in their environmental stabilities, but all seem to be susceptible to one or more modes of decomposition including photolysis, microbiological degradation, and plant metabolism. 

Gas may be formed by microbiological degradation of organics, evaporation and volatilization of volatile materials, or chemical reactions. The high combustibility of methane—a major component of landfill-generated gas—is a potential hazard. The emission of gas can be accelerated by elevated temperatures and venting conditions. Air pollution, which may result from gaseous... 

Environmental conditions determine in large part the chemical reactions that will occur when waste is injected. For example, precipitation-dissolution reactions are strongly controlled by pH. Thus, iron oxides, which may be dissolved in acidic wastes, may precipitate when injection-zone mixing increases the pH of the waste. Similarly, redox potential (Eh) exerts a strong control on the type of microbiological degradation of wastes. 

Shukla, O. P., Microbiological Degradation of Quinoline by Pseudomonas-Stutzeri - the Coumarin Pathway of Quinoline Catabolism. Microbios, 1989. 59(238) pp. 47-63. 

Each type of technique can be applied in several modifications. Microbiological degradation processes offer the possibility to purify wastewater streams which contain a wide range of organic pollutants. In contrast, physical/chemical techniques are much more specific. The quality of the purified water regarding residual amounts of soluble organic pollutants, and colloidal and suspended particle pollutants, strongly depends on the type of treatment process and the applied treatment conditions. Very often a combination of different types of treatment techniques is necessary to satisfy the effluent quality required (for example a combination of anaerobic and aerobic treatment). 

The presence of free anilines or other metabolites in soils and plants has been reported [123, 139-143]. Some work has suggested that they are very strongly bound to soil components and the findings of Caverly and Denney [138] are in agreement with these conclusions. The presence in soils of metabolites of Linuron that possess the urea structure have been reported [123, 142] these are produced mainly by microbiological degradation. The dimethyl derivative is considered to be inactive whereas the monomethyl metabolite has phytotoxicity approaching that of the parent herbicide [142], It is probable that the procedure reported by... 

Various soil remediation techniques such as incineration, soil washing, or biological soil treatment were applied in the past, but the microbiological degradation of TNT-contaminated soils is considered to be the most favorable technique as far as costs are concerned [414]. The following is a summary of these TNT remediation technologies ... 

Smith, A.E. and Cullimore, D.R. Microbiological degradation of the herbicide dicamba in moist soils at different temperatnres. 

Walker, W.W. Chemical and microbiological degradation of malathion and parathion in an estuarine environment, J. Environ. 

Evidence for the microbiological degradation of 2,4-D ester in soils was based on the stimulation by warm, moist conditions and organic matter (19) a correlation between degradation rate and the numbers of aerobic soil bacteria (20) and inhibition when the soils were air-dried and autoclaved (iTT. Little information is available, however, on the nature of the degradation products. 

The process can be used as a pretreatment for bioremediation, breaking apart complex organic compounds to facilitate microbiological degradation. 

In landfarming, a layer of contaminated soil is spread out on a specifically constructed site. Microbiological degradation is stimulated by soil tilling, irrigation, and addition of nutrients (nitrogen, phosphorus) and a specialized inoculum, if necessary. When the pollutant concentration is reduced to the target level, a new layer of polluted soil is spread and treated. 

The process produces no air emissions. Because this is an aqueous-based technology, neither NO, nor SO is produced. The delivery system is closed so no volatilization of toxic organic compounds occurs. The electron beam can be used efficiently and effectively as pretreatment for biological remediation. The electron beam can break complex organic compounds, making them suitable for microbiological degradation. 

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