Biodegradation of PAHs 9431 PAHs Dissolved in Water

Because of their low solubility in water and the frequently rate-limiting dissolution of crystals, PAH biodegradation can be more easily studied by using solving agents such as dimethylsulfonoxide (DMSO; Cuno 1996). With the help of DMSO, the solubility of acenaphthene can be increased remarkably. Figure 9.5 shows the results of a batch experiment with a mixed culture of PAH-degrading bacteria. The concentration of the culture using acenaphthene as an energy and carbon source could not be measured. Therefore, in the solution of the model:

dX S

assumptions must be made for YX/S and kd. The line in Fig. 9.5 shows the solution which agrees with the experimental data very well. Table 9.8 shows some further kinetic coefficients for the aerobic biodegradation of acenaphthene and other PAHs. The maximum growth rate decreases from naphthalene over phenan-threne, acenaphthene to anthracene. Further results for PAHs with four rings were published by Cuno (1996).

Fig. 9.5 Biodegradation of acenaphthene dissolved in water using a solving agent (5 vol% dimethylsulfonoxide; Cuno 1996), modelled using Eqs. (9.2) to (9.3).

Time t

Fig. 9.5 Biodegradation of acenaphthene dissolved in water using a solving agent (5 vol% dimethylsulfonoxide; Cuno 1996), modelled using Eqs. (9.2) to (9.3).

Table 9.8 Stoichiometric and kinetic coefficients for aerobic degradation of some PAHs.

Reference Bacteria Compound YJ/S ^max KS kd

Wodzinski and

Pseudomonas sp.

Naphthalene

0.5a)

7.2

Johnson (1968)

Guha and

Mixed culture

Phenanthrene

0.3a)

0.026

0.09

Jaffé (1996)

Springfellow

P. stutzeri

Phenanthrene

0.24

and Aitken (1995)

Komatsu et al.

Pseudomonas sp.

Acenaphthene

2.8

(1993)

Cuno (1996)

Mixed culture

Acenaphthene

0.7b)

1.48

0.065 0.0048

Breure et al.

Pseudomonas sp.

Anthracene

0.072

0.048

(1990)

Cuno (1996)

Mixed culture

Anthracene

0.55

0.18

The cometabolism of two PAH by a pure culture was studied by Springfellow and Aitken (1995). Pseudomonas stutzeii is able to use both naphthalene and phe-nanthrene as the only source for carbon and energy. The influence of both substrates on the oxygen consumption rate could be described by using a model for competitive inhibition:

with S as the concentration of phenanthrene and Si as the concentration of naphthalene.

0 0

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