As the presence of emergent contaminants in wastewater, such as antibiotics, has become a threat for public health, the evaluation of strategies to treat them has been gaining importance. A critical example of this situation can be found in wastewaters coming from the pharmaceutical industry, where high concentrations of antibiotics are sometimes accompanied by high organic contents. Even the agroindustry can be affected by a similar problem when cattle infections are treated with antibiotics and part of the antibiotic-contaminated milk has to be wasted. With these situations in mind, in the present study we evaluated a progressive acclimation strategy for a granular sludge in a UASB reactor treating a high organic-content synthetic wastewater contaminated with azithromycin. In parallel, we tested a previously reported low-cost method for azithromycin determination by spectrophotometry, obtaining results comparable with liquid chromatography coupled to mass spectrometry. Although azithromycin has been reported as recalcitrant and resistant to biological degradation, the antibiotic was removed with efficiencies over 50% for wastewater with 10 mg L-1 of azithromycin and a COD of more than 4000 mgO2 L-1. Furthermore, efficiencies over 40% were achieved for wastewater with higher azithromycin concentrations (80 mg L-1) and a COD of 20,000 mgO2 L-1. A careful acclimation strategy permitted the partial removal of azithromycin from wastewater when treating concentrations comparable and higher than what would be expected for domestic and hospital wastewaters, even when its chemical oxygen demand is considerably higher than the average maximum of around 1000 mgO2 L-1.
Keywords: Anaerobic digestion; Antibiotics; Emergent contaminants; High organic load; Spectrophotometry.
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