Degradação anaeróbia de benzeno na presença de etanol, oxigênio e importantes intermediários

Abstract

The present work aimed to evaluate the interference of the addition of different intermediate compounds of the anaerobic benzene degradation (phenol, benzoate, and toluene) and the co-substrate ethanol in the removal of this monoaromatic hydrocarbon under anaerobic and microaerobic conditions. The experiment was divided into two phases. In Phase 1, the effect of the presence of ethanol (1 g COD·L-1 ) and oxygen (1.77 mg∙L-1 ) on the anaerobic benzene degradation was investigated. In Phase 2, the effect of the presence of important intermediates (phenol, benzoate, and toluene, individually tested at 5 mg∙L-1 ) on anaerobic and microaerobic (1.77 mg O2∙L -1 ) benzene degradation was investigated. All tests were carried out in batch (in duplicate, 150 rpm and 30 °C), with a reaction volume of 70 mL (basal medium + inoculum), in borosilicate glass bottles (115 mL) inoculated with anaerobic sludge (2 g SSV∙L-1 ) adapted to benzene and microaerobic conditions. In general, the presence of co-substrate negatively affected the anaerobic benzene degradation, while the addition of oxygen did not significantly improve the removal of this compouns. At the end of all tests, it was found that the addition of the intermediates negatively influenced the degradation of benzene, with benzoate being the intermediate that presented the greatest interference and toluene the least interfering. In all batch tests with the presence of the intermediates phenol, benzoate, and toluene, the main degradation pathway was hydroxylation, showing that, most likely, benzene was converted, first, to phenol and, subsequently, to benzoate, the key intermediate of anaerobic degradation of aromatics.