Degradation of chlorotetracycline and bacterial disinfection in livestock wastewater by ozone-based advanced oxidation

The simultaneous removal of antibiotics and antibiotic-resistant bacteria by ozone-based advanced oxidation technology (AOT) was investigated for the treatment of anaerobic digestion effluent of piggery wastewater. Chlorotetracycline (CTC) and CTC-resistant bacteria were selected as targets since CTC has been the most used antibiotics in livestock industries in Korea. The performance of four different combinations of oxidation agents was investigated, showing the order of removal rate as O3 < O3/H2O2 < O3/UV < O3/UV/H2O2 for wastewater. Applications of O3/UV/H2O2 and O3/UV degraded almost all CTC within 15 and 20 min, respectively. Only 30% of CTC was degraded even in 40 min by O3 alone and O3/H2O2 degraded 65% of CTC in 40 min. The combination of ozone/H2O2 did not contribute significantly to CTC degradation, but the influence of UV was substantial when coupled with ozone. CTC was partially degraded during oxidation although main HPLC peak was completely vanished. The resulting intermediates of partially oxidized CTC possessed no more antibiotic capability, suggesting that CTC transformed into nontoxic organic constituents. For disinfection, ozone alone was not effective for disinfection; less than 2-log reduction was achieved in 1 h. UV was more superior in reducing bacterial population, showing more than 4-log reduction in 20 min and 5-log reduction in 40 min. UV was also effective in reducing both total and CTC-resistant bacterial population, and the contribution ratio of UV to ozone was about 3:1 in logarithmic scale. The application of O3/UV together further enhanced the disinfection performance compared to UV alone.