ABSTRACT
Benzene represents an environmental and health risk because it has high solubility and mobility in water and also has carcinogenic properties. It is considered one of the most recalcitrant compounds among the aromatic hydrocarbons in anaerobic environments. Despite the investigations already conducted, the effect of important intermediates using mixed cultures as anaerobic sludge is still quite controversial. From this perspective, the objective of this research was to evaluate the influence of ethanol as a co-substrate and the addition of anaerobic benzene degradation by-products (i.e., phenol, benzoate, and toluene). The experiments were carried out in borosilicate glass bottles (115 mL) with a reaction volume of 70 mL (basal medium + microorganisms) inoculated with acclimatized anaerobic sludge (2 g VSS·L−1). Benzene removal was accelerated when ethanol was used as a co-substrate, with the consumption rate increasing from 0.0445 mg·L−1·day−1 (without ethanol) to 0.0563 mg·L−1·day−1 (with ethanol), suggesting the participation of cometabolic processes. Benzene was removed with the subsequent formation of phenol and benzoate, consumed later, with no accumulation of by-products in the medium. Finally, intermediate addition negatively influenced benzene removal, with benzoate showing the greatest interference (~55% reduction), as it is a key intermediate in the anaerobic benzene removal.
Keywords:
anaerobic digestion; benzene; benzoate; phenol; intermediates
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