Biodegradation Results

The concentrations of CO2 vary during the experiment and demonstrated a cyclic nature of biodegradation. The concentration of CO2 was higher at the beginning of the test and then slowly decays over the course of the experiment. 

The concentration of carbon dioxide gas in ppm can be converted to percentage biodegradation by calculating the mass of carbon produced and then dividing by the initial mass of carbon in the sample. Equation D. 1 lists the conversion factor from carbon dioxide gas concentration to grams of carbon produced. The ppm concentration is divided by 10,000 to convert the ppm to volume fraction of carbon dioxide gas. The volume fraction of carbon dioxide gas is multiplied by the liters of free air of gas and then by the density of carbon dioxide to yield the mass of carbon dioxide. The mass of carbon dioxide is multiplied by the ratio of the atomic mass of carbon and the molecular mass of carbon dioxide. 

The biodegradation rate can be determined from the amount of CO2 measured during the 180-day experiment and the amount of initial carbon present in the sample with the use of Equation A.I. The CO2 was measured according to the procedure outlined previously. 

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Biodegradation results from the pH drop such a detergent polymer experiences as it leaves the alkaline laundry environment (pH ca 10) and enters the sewage or ground water environment (pH close to neutral) the polymer (now a polyacid rather than a salt) is unstable and hydrolyzes to monomer which rapidly biodegrades. The chemistry has been reported ia many patents (186) and several pubHcations (187,188). 

Schoberl et al. reported the data compiled in Germany for the most important industrial surfactants [383]. Natural and oxoalcohol sulfates have primary biodegradation results of 99% and 98-99%, respectively, by the confirmatory test. Natural and oxoalcohol ether sulfates biodegrade 98-99% and 96%, respectively, in the confirmatory test. Reported values of total biodegradation are shown in Table 35A and Table 35B. 

Substance Biodegradation results Biodegradation category Reference... 

Biodegradation. Under aerobic conditions, biodegradation results in the mineralization of an organic compound to carbon dioxide and water and—if the compound contains nitrogen, sulfur, phosphorus, or chlorine—with the release of ammonium (or nitrite), sulfate, phosphate, or chloride. These inorganic products may then enter well-established geochemical cycles. Under anaerobic conditions, methane may be formed in addition to carbon dioxide, and sulfate may be reduced to sulhde. 

Much of the testing involves looking at real-time biodegradation results on physical properties. There is an effort to develop standardized tests that can be done outside a patient with this effort now being done by comparing the tests done outside the patient with results found with the patient. 

Gibson, S. A. Suflita,J. M. (1986). Extrapolation of biodegradation results to groundwater aquifers reductive dehalogenation of aromatic compounds. Applied and Environmental Microbiology, 52, 681-8. 

Although plastic wastes in refuse are highly visible to the public, and thus have caused considerable consumer pressures on plastics manufacturers to take anti-pollution measures, disposal of plastics creates special problems in municipal incinerators because of the formation of some toxic gases, hi terms of dumpsite disposal, the absence of biodegradability results in long-term solids buildup. Actually, on a weight basis, however, plastics only comprise 7% of municipal wastes, as shown in Table 4. 

In pure cultures of microorganisms, the products of cometabolism tend to accumulate and often do not undergo further degradation. However, in mixed cultures, which are the norm for environmental systems, they may serve as substrates for other organisms so that complete biodegradation results. Therefore, studies of biodegradation in pure cultures are usually of limited utility in predicting what happens in the environment. 

In the ambient atmosphere, chlorobenzene will exist as a vapor, and will be degraded by reaction with photochemically produced hydroxyl radicals, with an estimated half-life of 21 days. Photolysis half-lives of 4-18 h were measured in aqueous media. Chlorobenzene is expected to volatilize from soil, and is predicted to have high mobility based on the Kqc values. Biodegradation results are variable based on soil type and bacteria type. In river water, the biodegradation half-life was reported to be 150 days, and 75 days in the sediment. Volatilization is expected to occur from water surfaces. Hydrolysis is not predicted to occur. 

The low concentrations of the pollutants in the feed phase start to be biodegraded, resulting in a decrease of the pollutant concentration in the feed phase. Thus the partitioning equilibrium of the pollutant, between the diluent and the feed phase, is disturbed. The pollutant is transported back into the feed phase at finite rates determined by the rate of biodegradation there [8], as well as the respective value of PDiiuent/Peed phase [1], as defined in Eq. (1). 

BiodegradabOity of polymers means limited durability of the products made thereof especially in humid environments For most applications biodegradability results in less durable, lower performance products. In order to make a... 

The sodium alkylbenzenesulfonates are an important class of detergents. The original ones made by alkylating benzene with propylene tetramer did not biodegrade, resulting in foaming rivers, and such.268 The current linear alkylbenzenesulfonates (8.46) made from a-oleflns are biodegradable. 

Figure 1. Different patterns of biodegradation resulting from microbial adaptation. (A) Adaptation to p-nitrophenol in Lulu aquifer samples at 529 ng/mL, but not at 14 ng/mL (41). (B) Adaptation to the triazinone-ring of metribuzin, evidenced by an increasing mineralization rate over time in the surface soil, but not in the subsurface soils (351. (C) Adaptation to EPTC after long-term EPTC use (12). (Reproduced with permission from Ref. 12. 15, 43. Copyrights 1988, 1989, 1987 Weed Science Society of America, American Society of Agronomy, and American Society for Microbiology, respectively)...

Our work on biodegradation supports that of Yu et al. (2002). In particular, our models suggest that biodegradation is not necessarily limited to temperatures less than 65 °C that not all lower temperature reservoirs contain biodegraded oil and that the dynamic nature of biodegradation results in poor to very poor correlations between API gravity and reservoir depth or temperature. 

When the solid waste crisis hit the United States in the 1980s, plastics were often attacked as particular problems because they are nonbiodegradable. There was a perception that biodegradation resulted in recovery of valuable landflll space. Some states even passed laws requiring that certain types of plastics (usually merchandise bags) be degradable. 

Biodegradation. Current studies have shown that wet systems, or landfills that use leachate recirculation, are becoming the favored option when considering solid waste stabilization as a priority for the landfill. Since most biodegradation results from... 

Table 6.8. Biodegradation results of compostable polymer materials [159]...

The product is classified as not easily biodegradable (result of the closed bootle test duration 28 days). Fish toxicity LCq for Brachydanio rerio 0.26 mg/1 (96 h)... 

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