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A biorremediação é uma alternativa atraente para o tratamento de solos contaminados com hidrocarbonetos de petróleo. No entanto, a efetividade do processo pode ser limitada não só pelas características do contaminante, mas também pela sua biodisponibilidade. Este trabalho tem como meta o estabelecimento de procedimento preliminar para identificar o fator principal (recalcitrância ou biodisponibilidade) que interfere negativamente na biodegradação, resultando em baixas eficiên-cias. Foram realizados testes em microcosmos contendo solo aplicando as técnicas de bioestímulo e bioaumento. Experimentos semelhantes foram conduzidos em meio líquido contendo óleo cru e microorganismos extraídos do solo contaminado, nutrientes e inóculo microbiano (Rhodoturula glutinis e Nocardia nova). Após 30 dias, o maior nível de biodegradação (98.8%) foi obtido na condição com bioaumento em meio líquido, indicando que o problema principal de biodegradação de hidrocarbonetos de petróleo pode estar associado à baixa biodisponibilidade destes no solo e não apenas a recalcitrância intrínseca do poluente residual.Bioremediation is an attractive alternative to treat soils contaminated with petroleum hydrocarbons. However, the effectiveness of biodegradation process can be limited by both contaminant characteristics and its bioavailability in soil. This work aims at establishing a preliminary procedure to identify the main factor (hydrocarbon recalcitrance or its bioavailability) that impairs the biodegradation, possibly resulting in low remediation efficiencies. Tests in soil microcosms were carried out applying biostimulation and bioaugmentation techniques. Similar experiments were conducted using liquid medium containing crude oil and microorganisms, both of them extracted from a weathered contaminated soil sample, nutrients and microbial inoculum constituted of Rhodoturula glutinis and Nocardia nova. After 30 days, highest microcosms biodegradation levels (98.8%) were obtained with bioaugmentation in liquid medium, pointing out that the main problem of petroleum hydrocarbon utilization by microorganisms was associated to its availability and not only to the intrinsic recalcitrancy of remaining pollutants.

BACKGROUND: Oil spills are a frequent source of environmental contamination. As a consequence, remediation of soils, waters and sediments is a great challenge in this area of research. This study aims at using a new type of soil bioreactor (13 L bench-scale and 800 L pilot-scale) to treat tropical soil contaminated with petroleum. Additionally, it includes the evaluation of the effectiveness of two auxiliary techniques: bulking agent addition (sawdust) and biostimulation using two different nitrogen sources (sodium nitrate and urea).

Reticulated vitreous carbon 45 pores per inch is adopted to deposit copper(II) from dilute solutions of 10-20 ppm to below 1 ppm. Three working potential values are tested: E ) -0.4 V and E ) -0.5 V, at which metal deposition is under diffusion control, and E ) -0.25 V, at which the effect of O 2 reduction is limited, but deposition does not occur at its maximum rate. A theoretical model, which takes into account the reabsorption of O 2 from air, is proposed to interpret the trend of faradic yield as the metal concentration in the solution becomes lower. The behavior of the system is correctly interpreted from the model when electrolyses are performed at E ) -0.4 V.