Biodegradation in water

Ultimate biodegradation of the halogenated aliphatic acids, aldehydes, etc. such as mono-, di- and tri-chloroacetic which result from the metabolism of chlorocarbons by mammals, and from some atmospheric chemical reactions, is well established [43]. 

Both the rate and the extent of biodegradation of contaminants reported in the literature depends on the experimental conditions under which the measurement was made, and the results may not be applicable to other scenarios. Some results, for example, were derived from aerobic waste-water treatment facilities that have been optimized in terms of nutrient content, microbial acclimation, mechanical mixing of the reactants, and temperature. Hence, the results of such studies may under-predict the persistence of chemicals in a major spill onto soil or in groundwater beneath a waste site. 

Of the 23 plasticizers in Table 18.1, it appears that seven of the compounds can be biodegraded in surface water at rates that yield estimated half-lives of one to 56 days, and in groundwater with half hves from less than one day to about one year (Table 18.11). Although the wide range in half-lives reflects, in part, the variability of the conditions imder which the data were collected, it appears that butyl benzyl, di-n-butyl, and dimethyl 

Diallyl, dihexyl, diisobutyl, diisodecyl, diisononyl, diisooctyl phthalates, and acetyl tributyl citrate Expected based on limited studies (5,14)  

Diundecyl phthalate Half-life in surface water about 2.5 weeks (17)  

Tricresyl phosphate Half-life of several days in surface water (5)  

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Wang, P., Woodward, C.A., and Kaufman, E.N., Polyethylene glycol)-modified ligninase enhances pentachlorophenol biodegradation in water-solvent mixtures, Biotechnol. Bioeng., 64, 290-297, 1999. 

Finally, degradation processes which are usually assumed to be first order are not. Degradation in soil has been shown by Hamaker (27) to often behave in a biphasic manner. Biodegradation in water has been shown to more closely follow second order kinet-ics(28). Photolysis in solution is highly dependent on antenua-tion of light in the water body which will depend on water quality... 

Further biodegradation in water, sediment and soil covering degradation rate and identification of relevant degradants... 

Hexanone is a ketone, and ketones are generally not degraded by hydrolysis (Lande et al. 1976 Morrison and Boyd 1974). Based on its reactions in air, it seems likely that 2-hexanone will undergo photolysis in water, however no information was located. Based on studies with microorganisms (see Section 5.3.2.3), it is probable that 2-hexanone will be biodegraded in water. 

Data regarding the transformation and degradation of hexachlorobutadiene in soil were not located. However, based on the observation that hexachlorobutadiene was completely biodegraded in water under aerobic conditions (Tabak et al. 1981), biodegradation probably occurs in nonarid soils as well. 

Insufficient data are available to predict the relative importance of biodegradation in water. 

Surface water biodegradation ty, = 2.21 d in an acclimated shake flask COj evolution test (Sugatt et al. 1984) G 2 d to > 2 wk for aerobic biodegradation in water ty, = 3 d when incubated in dirty river water (Howard 1989) ... 

Bromotrichloromethane is expected to adsorb to suspended solids and sediment in water. Volatilization from water surfaces is expected. The potential for bioconcentration in aquatic organisms is moderate. Based upon the highly halogenated structure of bromotrichloromethane, biodegradation in water is expected to be slow. 

Emitted ethene is distributed primarily into the atmosphere and reacts with photochemically reactive hydroxyl radicals, ozone, and nitrate radicals, with half-lives ranging from 1.9, 6.5, and 190 days, respectively. Biodegradation in water occurs with half-lives in the range of 1-28 days, or under anaerobic conditions, 3-112 days. Bioaccumulation in aquatic organisms is not expected to occur, based on ethene s high vapor pressure and log octanol/wa-ter partition coefficient. 

MIBK has a short half-life in the atmosphere and is also biodegraded in water. It is not expected to bioaccumulate. Based on an experimental vapor pressure of 19.9 mmHg at 25°C, MIBK is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase MIBK is degraded in the atmosphere by reaction with photochemically produced hydroxyl radicals with an estimated atmospheric half-life of 27h. Methyl isobutyl ketone is expected to have high mobility in soils based upon an estimated Kqc value of 123. Volatilization from dry soil surfaces is expected based upon the vapor pressure of this compound. 

Limited data indicate that caffeine has the potential to biodegrade in soil. If released into water, caffeine will not volatilize from water to the atmosphere. It will not bioconcentrate in fish nor will it adsorb to sediment. Limited data indicate that caffeine has the potential to biodegrade in water. 

The rate of PCB biodegradation in water is dependent on both individual congener structure and environmental eonditions, as is explained in more detail in Section 6.3.2.3. Biodegradation in surface waters is primarily an aerobic process in some, partieularly oligotrophic waters, a substantial percentage of the total PCB eoncentration can be found in the dissolved phase (see Section 6.3.1 Eisenreich et al. 

RDX undergoes biodegradation in water and soil under anaerobic conditions. Its biodegradation products include hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX) hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) hydrazine ... 

PROBABLE FATE photolysis-, aqueous photolysis is not expected to be important, reaction with photochemically produced hydroxyl radicals has a half-life of 13.44 hr, direct photolysis is not expected to be important since it should not adsorb wavelengths >290 nm oxidation photooxidation is not expected to be important, photooxidation only in atmosphere, photooxidation half-life in air 9.65 hrs-4.02 days hydrolysis very slow, maybe significant, hydrolysis of carbon-chloride bonds, release to water results in hydrolysis with a half-life of 40 days when released to soil, it may hydrolyze hydrolyzed slowly in aqueous dimethylformamide at pH 7, first-order hydrolytic half-life 22yrs volatilization expected to volatilize if released to water, volatilization half-lives from lakes, rivers, and streams 3.5, 4.4, and 180.5 days respectively sorption not an important process biological processes biodegrades in water after several weeks of acclimation, biodegradation not important under natural conditions, no bioaccumulation noted... 

Toxic to sewage organisms. Biochemical oxygen demand (BOD 5) 0.0 g 02/g. The substance shows no evidence for biodegradability in water. 

As the polyvinyl chloride (PVC) and PET, PHB exhibits good barrier properties and can be used for packaging application and in the medical field as a biodegradable plastic that could solve euviromneu-tal problems due to their biodegradability in water and in carbon dioxide [2,4],... 

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