Methanogenic conditions

Degradation of trichloroethylene by anaerobes via reductive dehalogenation can be problematic because a common product is vinyl chloride, a known carcinogen (Ensley 1991). In an anaerobic colunm operated under methanogenic conditions, 100% transformation of injected tetrachloroethylene and trichloroethylene to... 

Freedman DL, Gossett JM. 1989. Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions. Appl Environ Microbiol 55 2144-2151. 

Vogel TM, McCarty PL. 1985. Biotransformation of tetrachloroethylene to trichloroethylene, dichloroethylene, vinyl chloride and carbon dioxide imder methanogenic conditions. Appl Environ Microbiol 49 1080-1083. 

Under methanogenic conditions, a strain of Methanosarcina sp. transformed tetrachloroethene to trichloroethene (Fathepnre and Boyd 1988). In the presence of suitable electron donors snch as methanol, complete rednction of tetrachloroethene to ethene may be achieved in spite of the fact that the dechlorination of vinyl chloride appeared to be the rate-limiting step (Freedman and Gossett 1989). 

Middeldorp PJM, M Jaspers, AJB Zehnder, G Schraa (1996) Biotransformation of a,[5,y, and 5-hexachloro-cyclohexane under methanogenic conditions. Environ Sci Technol 30 2345-2349. 

In anaerobic microcosms, l,l,2-trichloro-l,2,2-trifiuoroethane (CFC-113) was transformed by successive reductive dechlorination to l,2-dichloro-l,2,2-trifiuoroethane (HCFC-123a), and under methanogenic conditions to l-chloro-l,2,2-trifiuoroethane (HCFC-133) and l-chloro-l,l,2-triflnoroethane (HCFC-133b) without evidence for the reductive replacement of fluorine (Fignre 7.70b) (Lesage et al. 1992). 

Bisaillon J-G, F Lepine, R Beaudet, M Sylvestre (1991) Carboxylation of o-cresol by an anaerobic consortium under methanogenic conditions. Appl Environ Microbiol 57 2131-2134. 

Somsamak P, HH Richnow, MM Haggblom (2006) Carbon isotope fractionation during anaerobic degradation of methyl tert-butyl ether under sulfate-reducing and methanogenic conditions. Appl Environ Microbiol 72 1157-1163. 

At many sites, the subsurface environment will be anoxic or even anaerobic due to the activity of aerobic and facultatively anaerobic bacteria in the surface layers of the soil. It is therefore essential to take into consideration the extent to which anaerobic degradation may be expected to be significant. Reactions may take place under sulfidogenic or methanogenic conditions, and the occurrence of sulfate at sites containing building material waste and the metabolic versatility of sulfate-reducing bacteria makes them particularly attractive. 

Details of the anaerobic degradation of chloroalkanes and chloroalkenes have been discussed in detail in Chapter 7, Part 3, and the application of reductive processes to bioremediation has been examined under denitrifying, sulfidogenic, and methanogenic conditions. An important observation... 

Bouwer, EJ. and McCarty, P.L., Transformations of 1- and 2-carbon halogenated aliphatic organic compounds under methanogenic conditions, Appl. Environ. Microbiol., 45, 1286-1294, 1983. 

The fate of hormones during sludge treatment has been also poorly documented. Two surveys based on full-scale anaerobic reactors treating sludge concluded that hormones were poorly eliminated or not at all in methanogenic conditions [85, 111]. These results are in accordance with laboratory experiments performed in... 

Ejlertsson J, Alnervik M, Jonsson S, Svensson BH (1997) Influence of water solubility, side-chain structure on the degradation of phthalic acid esters under methanogenic conditions. Environ Sci Technol 31 2761-2764... 

Gu J, Fan Y, Gu J-D (2003a) Biodegradability of atrazine, cyanzine and dicamba under methanogenic conditions in three soils of China. Chemosphere 52 1515-1521... 

Mixed, mesophilic methanogenic culture Reactive red 1 Bottles Batch Methanogenic conditions F 50-2,000 35 7... 

Anaerobic sludge from a full- scale UASB Acid orange 7 direct red 254 UASB Continuous Methanogenic conditions B Sludge granules 60-1,800 37 n.a. 

Beydilli MI, Pavlostathis SG (2005) Decolorization kinetics of the azo dye Reactive Red 2 under methanogenic conditions. Effect of long-term culture acclimation. Biodegradation... 

Razo-Flores E, Luijten M, Donlon B, Lettinga G, Field J (1997) Biodegradation of selected azo dyes under methanogenic conditions. Water Sci Technol 36 65-72... 

Methanesulfonyl chloride, 23 653, 681-683 Methano[60]fullerenes, 12 242 Methanogenic conditions, defined, 3 757t Methanoic acid, physical properties, 5 29t Methanol, 16 299-316. See also Methanol synthesis... 

Reductive dechlorination or reductive hydrogenolysis is a common transformation of 1- and 2-carbon chlorinated aliphatics under methanogenic conditions [373,374]. 1,1,1-Trichloroethane (l,l,l-TCA),for example,is converted to 1,1-dichloroethane (1,1-DCA) [375], and Perchloroethylene (PCE) is successively converted to TCE, cDCE, VC, and ethane [274]. Each reductive dechlorination is a two-electron transfer reaction. 

Bouwer and McCarty [374] suggested 1,1,2-TCA is an intermediate of TeCA transformation in continuous-flow column experiments and TCE as an intermediate in a batch experiment under methanogenic conditions. Those transformations are reductive dechlorination and dehydro chlorination, respectively. 

Mineralization of Dicamba was demonstrated under methanogenic conditions and the degradation pathway elucidated. 

Bedard et al. [245] reported that PCB dechlorination was stimulated by adding 2,5,3, 4 -tetrachlorobiphenyl (25-3 4 -CB) to slurries (incubated under methanogenic conditions) of sediments contaminated with Aroclor 1260 from Woods Pond (MA). The 25-3 4 -CB was converted stoichio-metrically to 25 - 3 -CB and stimulated a selective para-dechlorination which decreased the penta- through heptachlorobiphenyls containing 234-, 245-, or 2345-chlorophenyl groups by up to 83% in 12 weeks. 

---