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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Several studies were reported on different water or sediment systems as activated sludge, enriched sawage, settled domestic waste water, digester sludge, pure cultures, waters.
The only data of half-life is in aerobic and anaerobic waters, where was reported 68 days and 2.8 days of biodegradation, respectively.
 

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Several studies were reported on different water or sediment systems.

In general, complete or partial biodegradation of 2,4-DNP was observed under aerobic conditions with mixed microorganisms from activated sludge (Kincannon et al. 1983a, 1983b; Patil and Shinde 1989; Pitter 1976), enriched sewage(Brown et al. 1990; Wiggins and Alexander 19SS), adapted sediment from rivers or waste lagoons (Barth and Bunch 1979; Chambers et al. 1963; Tabak et al. 1964).

In a study with activated sludge previously adapted to mineralize low concentrations of dinitrophenols, 95% biodegradation of 10 mg/L of 2,4-dinitrophenol in about 4 hours was obsterved, but when the substrate concentration was increased to 75 mg/L no degradation was observed over 25 hours (Jo KW, Silverstein J, 1998).

In settled domestic waste waterbiodegradation of 2,4-DNP was observed in a static incubation of 5 and 10 mg/L of 2,4-dinitrophenol. Biodegradation resulted at 60 and 68%, respectively, in 7 days (Tabak HH, Quave SA, Mashni CI, et al 1981).

The biodegradation of 2,4-DNP under methanogenic conditions with anaerobic digester sludge was observed with little or no inhibitory effect at concentration ≤20 mg/L. As the concentration of 2,4-DNP increased to >100 mg/L, however, the microorganisms needed an adaptation period of 40-90 days before the commencement of biodegradation (Battersby and Wilson 1989; O’Connor and Young 1989).

The half-life of 2,4-dinitrophenol in an aquifer slurry was about 5 days under both methanogenic and sulfate-reducing conditions, but was not biodegraded under nitrate-reducing conditions (Krumholz LR, Suflita JM).

2,4-DNP is biodegraded by several pure cultures of microorganisms, such as Pseudomonas sp.(Bruhn et al. 1987; Sudhakar-Barik et al. 1976), Scenedesmus obliquus(Klekner and Kosaric 1992), Haloanaerobium praevalens, Sporohalobacter marismortui (Oren et al. 1991),Fusarium oxysporum(Madhosingh 1961) two strains of Rhodococcus sp.(Lenke et al. 1992; Schmidt et al. 1992), Janthinobacterium sp.(Gier et al. 1989; Hess et al. 1990; Schmidt et al. 1992), Corynebacterium simplex (Gundersen and Jensen 1956; Jensen and Gundersen 1955) a gram-positive bacterium (Suwa et el. 1992), and a filamentous bacterium (Schmidt et al. 1992) isolated from soil, water, and sediment.

DNP is also anaerobically biodegraded by Veillonella alkalescensinthe presence of hydrogen (McCormick et al. 1976).

A sulfate-reducing bacterium, Desulfovibrio sp., isolated from a continuous anaerobic digester, used 2,4-DNP as sole source of nitrogen but not of carbon and energy for growth (Boopathy and Kulpa 1993). The biodegradation by anaerobic organisms and under anaerobic conditions proceeded by reduction of nitro groups to amino groups (Madhosingh 1961; McCormick et al. 1976). The bacterium Desulfovibrio sp. reduced the nitro groups in 2,4-DNP to amines and reductively deaminated the amino groups, leaving the aromatic ring intact with the formation of phenol (Boopathy and Kulpa 1993).

Usually, the pure cultures were able to biodegrade 2,4-DNP after a certain adaptation period and as long as the concentration of 2,4-DNP was below a certain toxic level. The degradation pathway depended on the microorganisms and the conditions of aeration. Typically, with aerobic organisms and aerobic conditions, the biodegradation proceeded by replacement of nitro groups by hydroxyl groups and liberation of nitrite, or by hydroxylation of the aromatic ring positions 3, 5, or 6 (Raymond and Alexander 1971).

Although these pure culture studies are important for establishing degradative pathways, they do not reflect real environmental situations where mixed microorganisms and different nutritional conditions are present.

The only data of half-life is in aerobic and anaerobic waters, where was reported as 68 days and 2.8 days of biodegradation, respectively (Capel PD, Larson SJ, 1995).