The contamination of soil with polychlorinated biphenyl-containing industrial fluids is a worldwide environmental problem due to their high persistence. The present study aimed to elaborate a new strategy of process integration by the joint application of biosurfactant and combined chemical-biological treatment for soil decontamination. The addition of a microbial surfactant from Pseudomonas sp. PS-17 to the combined chemical-biological treatment, utilizing liquid hydrogen peroxide or calcium peroxide and a natural consortium of microorganisms-destructors, resulted in process modification that increased the treatment efficacy of soil contaminated with polychlorinated biphenyl-containing electrical insulating oil. A 42-d combined chemical-biological treatment supplemented by biosurfactant addition resulted in an average 47-50% of polychlorinated biphenyls removal - independent of the hydrogen peroxide carrier used. Changes in the soil pH during the combined treatment application with oxidizing chemicals in moderate dosages were unsubstantial. joint application of the biosurfactant, microorganisms and oxidizing chemicals in moderate dosages increased soil respiration and dehydrogenase activity compared to that obtained by application of the microbial consortium alone, indicating stimulation of microflora by the process integration. The application of the higher calcium peroxide doses (soil/CaO2 = 1/0.005, g/g) substantially increased the soil pH and diminished soil microbial respiration compared to that for untreated incubated soil. Ethylenediaminetetraacetic acid addition in the experiments with the solid hydrogen peroxide did not affect the treatment efficacy even after the prolongation of the treatment time from 1 to 42 d. Joint addition of both the biosurfactant and the chelating agent to the combined chemical-biological treatment was not effective. (C) 2013 Elsevier B.V. All rights reserved.