Estudo da biorremediação Ex situ de águas doces e salobras contaminadas com hidrocarbonetos aromáticos por meio de reatores microaeróbios

Abstract

The present work had the general objective to deepen the knowledge on the application of microaerobic bioreactors in the removal of BTEX for the development of an alternative ex situ bioremediation technology of fresh and brackish water contaminated with these compounds. For this purpose, the effect of different microaeration flows (0.5-2.0 mL ∙ min-1 air), injection points (feed and headspace) and effluent recirculation (0.7 L ∙ h -1) in microaerobic degradation of BTEX (~ 4.2 mg · L-1 of each compound) in a methanogenic bioreactor (TDH = 24 h). The influence of increasing concentrations of NaCl (0.15-3.64 g · L-1) on the microaerobic degradation of these compounds was investigated, and the effect of the presence of intermediates (phenol, benzoate and toluene) was evaluated. removal efficiency of benzene under anaerobic and microaerobic conditions. Finally, the effect of the presence of the cossubstrate ethanol (1 g COD · L-1), of different concentrations of dissolved oxygen (0.88-2.65 mg · L-1) and of the acclimatization of the inoculum sludge in the anaerobic degradation of BTEX. The microaeration ensured high removal efficiencies (> 83%) for all compounds, and the best results were obtained with 1.0 mL ar ∙ min-1, particularly for benzene, with a 30% increase in removal efficiency, at microaeration condition in the feed line. Effluent recirculation proved to be an important factor in improving mass transfer and, consequently, the removal of BTEX. The volatilization of these compounds was insignificant even under microaerobic conditions, suggesting that microbial activity was the main removal mechanism. When subjected to increasing concentrations of NaCl (0.15-3.64 g · L-1), the BTEX removal efficiency decreased, reaching a decrease of 18% for benzene when the highest concentration of NaCl (3, 64 g · L-1) was added. The study with the intermediates revealed that benzene degradation was negatively impacted by the presence of benzene, even under microaerobic conditions. Finally, the presence of cossubstrate negatively affected the anaerobic degradation of BTEX only for non-acclimatized sludge, while the addition of oxygen had a positive effect only for acclimatized sludge, the best results of which were obtained at the concentration of 1.77 mg ∙ L-1 , evidencing the importance of acclimatization of the microbiota to microaerobic conditions.