The cometabolic biodegradation of 4-chlorophenol by Stenotrophomas maltophilia KB2 strain in the presence of phenol as the growth substrate was studied. First, the ability of KB2 strain to biodegrade phenol as the only source of carbon and energy was tested for different initial concentrations of phenol changed in the range of 25–500 g·m-3. Haldane’s growth kinetic model was found to be the best to fit the experimental data so constants of the kinetic equation as well as the biomass yield coefficient were estimated (µ_m = 0,9h^-1, Ks = 48,97 g·m^-3, K = 256,12 g·m^-3, Y_x/s = 0,5715 g_x, g_g^-1). Next, a series of tests were carried out in dual-substrate system changing in a wide range the initial concentrations of phenol (50–300 g·m^-3) and 4-CP (25–100 g·m^-3); (S_g/S_c = 1–6). Total biodegradation was achieved for the whole range of changes of concentrations of both substrates and biodegradation time did not exceed 6 hours. The values of growth substrate transformation yield (T_c^g) and the (f) term, which means the fraction of reductant generated by phenol oxidation for 4-CP transformation were also estimated. The experimental database will be used to verify the mathematical model of the process.

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