Resumo

In recent decades, environmental problems caused by accidents with fossil fuels become more frequent. Remediation of sites polluted by petroleum hydrocarbons with microbial preparations is of special importance because it is simple to maintain, applicable over large areas, cost-effective and leads to the complete destruction of the contaminant. This study aimed to compare the biostimulation (BE) and bioaugmentation (BA) on the degradation of total petroleum hydrocarbons (TPH) in soils contaminated with 5% of diesel B5. All experiments were conducted in duplicate with the following treatments: control (C) (contaminated soil); biostimulation (contaminated soil with nutrients (NH4)2SO4 and K2HPO4, C: N: P ratio of 100:10:1); bioaugmentation (contaminated soil with nutrients and inoculation of indigenous microorganisms cultivated in BH medium with 1% of diesel B5). Contaminated soils (300 g samples) were placed in a set of polystyrene pan, and aerated by mixing. The microcosms was kept at room temperature, moistened every week and were sampled at 0, 34 and 62 days for chemical and microbiological analyses. Total petroleum hydrocarbon (TPH) was extracted from soil in Soxhlet extractor (USEPA 3540C) and was analyzed by gas chromatography with GC-MSD detector (USEPA 8015). Dilutions of the soil suspension were spread-plated (three replicates/dilution) on the PCA media for total aerobic heterotrophs. In relation to soil microorganisms was found for all microcosms an increase in the heterotrophics population, reaching 2.6 x10⁷ UFC.g^-1 soil (BE) and 4.2 x10⁷ UFC.g^-1 soil (BA). In both experiments, a higher proportion of the hydrocarbon component of diesel B5 was degraded compared to control. On average, 43,6% and 56,0% of TPH were degraded respectively for biostimulation and biaogmentation experiments. Indigenous microorganisms are well adjusted to their own environment. An immediate increase in the population density of these microbes could ensure rapid degradation of the pollutant. We conclude that the techniques employed (BE and BA) are intended to be used in bioremediation of soil contaminated with diesel B5, being significantly better than natural attenuation (control).