[Microbial decomposition of 3,4-dichloroaniline, adsorbed by activated charcoal]

The accessibility of 3,4-dichloroaniline (DCA) sorbed by activated carbon to degradative microorganisms was studied. A Paracoccus denitrificans strain capable of growing on medium with DCA as the only source of energy, carbon, and nitrogen was used in the experiment. The high sorption capacity of all the carbons studied (powdered RS and SKT-6A and granular AG-3) in relation to DCA (350 to 360, 480 to 520, and 540 to 580 mg/g, respectively) was demonstrated. The sorption capacity correlated positively with the specific surface area and the total volume of the sorbent micropores. The bulk of the DCA was reversibly sorbed and amenable to microbial decomposition; however, the decomposition rates significantly differed. When RS, SKT, and Agrosorb preliminarily saturated with DCA were incubated in a culture of P. denitrificans, the bulk of the reversibly sorbed DCA was decomposed (in the absence of the other carbon sources) in 2, 5, and 10 weeks, respectively, after which the process slowed down. At the end of the experiment (29 weeks), 81 to 87% of the DCA underwent full mineralization, which was accompanied by the release of chlorine ions; a small fraction of the xenobiotic (0.8 to 1.9%) remained a reversibly sorbed fraction (extractable with acetone), and 12 to 17% of the initial DCA seemed to have been chemically transformed and bound by carbon. The studied carbons may be used in biological decontamination of chloroaniline-polluted soils to decrease the toxic effect of chloroanilines on microorganisms.