Biodegradation of phenol, 2,4,6-trichlorophenol and pentachlorophenol was investigated using Dichomitus squalens cultivation media filtrates with initial laccase and manganese peroxidase activities of 1000 U L-1 and 300 U L-1, respectively. Decomposition of all three biocides was studied at T = 28 °C, pH = 4.5 and initial concentrations around 6 mg L-1 and the kinetics evaluated on the basis of the time course of the biocide concentration data. Integral analysis revealed 1st order reaction for

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... ll three pollutants and the corresponding reaction rate constants and initial concentrations for phenol, 2,4,6-TCP and PCP were estimated from linearized experimental data. The rate equations obtained allow estimation of the times necessary for a particular biocide conversion. The toxicity of reactants and products to the bacterium Vibrio fischeri before and after 48-hours degradation showed that the products were less toxic than the reactants in all three cases. The initial solutions of the three toxic substances caused 54 - 62 % inhibition of the bacterium Vibrio fischeri, while after 48 hours of degradation, 57 % reduction in the toxicity of phenol, 50 % reduction of 2,4,6-TCP and 29 % reduction of PCP was achieved.