Hydrogen peroxide-based wet oxidation to eliminate contraceptive hormone residues from pharmaceutical wastewater

Wet oxidation using hydrogen peroxide (1, 3, and 5% H₂O₂) at raised temperatures has been used to oxidize pharmaceutical wastewater derived from contraceptive pill production. Model wastewater containing ethinyl estradiol (40 μg/ml), levonorgestrel (25 μg/ml), cyproterone (25 μg/ml), gestodene (10 μg/ml), and desogestrel (50 μg/ml) was formulated based on the average concentration of hormones measured in the first wash of an equipment cleaning process. Higher temperatures for wet oxidation ranging from 100 to 150°C were anticipated to enhance the oxidizing capability of this hydroxyl-radical-mediated advanced oxidation. At mild oxidation treatments (1% H₂O₂ at 100°C), only sensitive species showed minor degradation by HPLC chromatogram. Desogestrel was easily removed even with this mild oxidizing, but the other hormones were more stable. Fortunately, higher temperatures generated much higher hormone degradation rates. For instance, 5% H₂O₂ at 150°C destroyed all the hormones in the model wastewater within 5 min. We assume highly reactive hydroxyl radicals produced the rapid mineralization of the spiked hormones.