Remoção de etanol e benzeno em reator anaeróbio horizontal de leito fixo na presença de sulfato / Ethanol and benzene removal in a horizontal-flow anaerobic immobilized biomass reactor in the presence of sulfate

Reator anaeróbio horizontal de leito fixo (RAHLF), preenchido com espumas de poliuretano, foi usado para tratar benzeno em solução etanólica, sob condições sulfetogênicas. Benzeno foi adicionado em concentração inicial de 2,0 mg.l-1, seguido de aumentos que variaram até 10 mg.l-1. O etanol foi adicionado em concentrações de 170 mg.l-1 a 980 mg.l-1. Soluções de sulfato ferroso e sulfato de sódio foram usadas, nas concentrações de 91 e 550 mg.l-1, respectivamente. O reator foi operado a 30 (± 2) ºC com tempo de detenção hidráulica de 12 h. A remoção da matéria orgânica foi próxima a 90 por cento com taxa máxima de degradação de benzeno de 0,07 mg benzeno.mg-1SSV.d-1. O presente trabalho corrobora os dados obtidos por Cattony et al (2005), na medida em que torna mais consistente a proposta do uso de unidades compactas de RAHLF, para a biorremediação in situ de compostos aromáticos.

In this study it is reported the operation of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor under sulfate-reducing condition which was also exposed to different amounts of ethanol and benzene. The HAIB reactor comprised of an immobilized biomass on polyurethane foam and ferrous and sodium sulfate solutions were used (91 and 550 mg.l-1, respectively), to promote a sulfate-reducing environment. Benzene was added at an initial concentration of 2.0 mg.l-1 followed by an increased to 9 e 10 mg.l-1, respectively. Ethanol was added at an initial concentration of 170 mg.l-1 followed by an increased range of 960 mg.l-1. The reactor was operated at 30 (± 2) ºC with hydraulic detention time of 12 h. Organic matter removal efficiency of 90 percent with a maximum benzene degradation rate of 0.07 mg benzene.mg-1VSS.d-1. Thus, this work corroborate the data obtained for Cattony et al (2005) and also demonstrate that compact units of HAIB reactors, under sulfate reducing conditions, are a potential alternative for in situ aromatic compounds bioremediation.

Metabolic responses of the teleost Hoplias malabaricus to high levels of environmental nitrite

The metabolic responses of Hoplias malabaricus to hypoxia caused by nitrite exposure was studied and compared to previous data of hypoxia caused by low environmental oxygen concentrations. These metabolic responses were analyzed from the contents of glycogen, glucose, lactate and pyruvate in liver, red and white muscle, heart and plasma. Glycogen mobilization provided clues to explain the metabolic behavior of the organism against internal hypoxia. The ratio of closely related metabolic intermediates was used to analyze its reaction displacement. The results permit us to conclude that H. malabaricus responds to nitrite hypoxia in the same way as when exposed to low oxygen external levels. That means hydrolyxis of hepatic glycogen followed by its synthesis in white muscle. Metabolism in the heart muscle seems to be more intense than in red muscle. Although internal and external hypoxia presented similar metabolic responses, the signiificance of this strategy remains uncertain.