Degradation, aerobic

Aerobic, Anaerobic, and Combined Systems. The vast majority of in situ bioremediations ate conducted under aerobic conditions because most organics can be degraded aerobically and more rapidly than under anaerobic conditions. Some synthetic chemicals are highly resistant to aerobic biodegradation, such as highly oxidized, chlorinated hydrocarbons and polynuclear aromatic hydrocarbons (PAHs). Examples of such compounds are tetrachloroethylene, TCE, benzo(a)pyrene [50-32-8] PCBs, and pesticides. 

Megharaj M, S Hartmans, K-H Engesser, H Thiele (1998) Recalcitrance of l,l-dichloro-2,2-bis (p-chlorophenyl)ethylene to degradation by pure cultures of 1,1-diphenylethylene-degrading aerobic bacteria. Appl Microbiol Biotechnol 49 337-342. 

Taurine is degraded aerobically either by a 2-ketoglntarate-dependent dioxygenation to aminoacetaldehyde (Kertesz 1999) (cf. degradation of 2,4-dichlorophenoxyacetate) or by transamination and fission by a lyase that is also nsed anaerobically with the formation of acetate (Cook et al. 1999). 

Since these reactions are relatively rapid, i.e., phenolic acids are rapidly degraded aerobically, their presence in the soil under these conditions appears transitory. It has been difficult to detect unbound phenolic acids in the soil solution and the compounds do not appear to accumulate in appreciable amounts under aerobic conditions. However, the soil is a heterogeneous medium consisting of loci or microenvironments that are at times completely opposite in character, i.e., anerobic microsites in a well-aerated soil (57). The phytotoxicity problem should be viewed in the context of a specially variable environment. 

You are concerned about the fate of 2-nitrophenol (NP) found at a concentration of about 10 ppb (0.07 /iM) in some groundwater. According to the literature (Zeyer and Kocher, 1988), this compound can be degraded aerobically by soil bacteria. The biodegradation pathway begins with an oxygenase that converts NP to catechol ... 

Biological soil treatment by landfarming is a relatively simple and inexpensive method for treating soil contaminated by compounds that are readily degraded aerobically (Table 1.2). Contaminated soil is evacuated and usually treated in pits lined with a high-density synthetic or clay liner (Figure 1.2). Perforated pipes can be placed in a layer of sand between the liner and contaminated soil to collect... 

DMS is degraded aerobically and anaerobically by microorganisms and its catabolism by pure and mixed cultures, or consortia, has recently been studied. 

Anaerobic degradation of PCB can occur with congeners containing up to seven chlorine atoms. It generally results in orf/io-substituted congeners, which can be further degraded aerobically. 

Methane Methane is readily degraded aerobically by methanotrophs, which are members of the domain Bacteria that form CO2 and H2O from the methane, using it as a source of energy and carbon. Methane may also be anaerobically degraded in some marine environments by a microbial consortium consisting of an archaeon (e.g. a member of the Methanosarcinales) and a eubacterium (e.g. a member of the Desulfosarcinales) (e.g. Orphan et al., 2001). The archaeon forms H2 and CO2 from the methane, and the eubacterium uses the H2 to reduce seawater sulphate to H2S. The overall reaction brought about by this consortium is ... 

Highly chlorinated PCBs and pesticides (e.g., mirex and DDT) may be dechlorinated anaerobically by functioning as an electron acceptor. DDT is dechlorinated to DDD by many facultative anaerobic microorganisms under anoxic conditions. DDD can be further dechlorinated or degraded aerobically. 

In Figure 23.1.7, a source releases VC and 1,2-DCA into the groundwater at a Type 3 site (an unlikely occurrence as more highly chlorinated solvents are typically released at sites). Because the VC and 1,2-DCA can be degraded aerobically, these constituents decline in concentration at a significant rate. Chloride is produced, and a depression in dissolved oxygen concentration similar to that occurring at fuel sites, is observed. 

Keywords biodegradation behavior, biodegradation standard, composting, abiotic degradation, biotic degradation, anoxic degradation, aerobic degradation... 

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