Biodegradability enhancement of real antibiotic metronidazole wastewater by a modified electrochemical Fenton

Abstract

This paper proposes a modified electrochemical Fenton method with a pair of iron electrodes, which Fe anode is electrodisolved supplying stoichiometric Fe2+. Then the electrodisolved Fe2+ reacts with H2O2 to generate hydroxyl radical (· OH). The experiment shows that 62.6% of chemical oxygen demand (COD) is removed and the ratio of the five-day biochemical oxygen demand (BOD5) to COD increases from 0.17 to 0.45 under the optimal experimental conditions (current density of 30 mA/cm2, electrolysis time of 15 min, H2O2 dosage of 75 mmol/L, pH 3.00 and stirring time of 2.5 hours). Meanwhile, the high concentration of metronidazole (1000 mg/L) is dramatically decreased (> 95%). In order to explore the mineralization pathway for metronidazole, the intermediate by-products of the modified electrochemical Fenton process are investigated by GC/MS, FTIR and HPLC. Good results are achieved in treatment of the real metronidazole wastewater by the proposed method, BOD5/COD increases from 0.17 to 0.35. This method has been successfully applied to a large scale industrial treatment of real metronidazole wastewater as a pretreatment process for the biochemical treatment.