Performance of a coupled micro-electrolysis, anaerobic and aerobic system for oxytetracycline (OTC) production wastewater treatment

BACKGROUND: The environmental and health effects caused by oxytetracycline (OTC) contamination of aquatic systems are a serious problem throughout the world. The OTC-contaminated wastewater cannot be treated effectively by conventional anaerobic and aerobic biological treatments. Few studies have investigated the systematic treatment of OTC-contaminated wastewater. RESULTS: A system including micro-electrolysis (ME), an expanded granular sludge bed (EGSB) and an anoxic/oxic activated sludge process (A/O) could treat OTC production wastewater effectively. First, a ME reactor packed with new ceramic-corrosion-cell fillers, serving as a pretreatment step, was effective in removing residual OTC and enhancing biodegradability of the wastewater. Second, EGSB and A/O reactors played the main role in removing chemical oxygen demand (COD), ammonium nitrogen (NH₃-N) and chroma (color of the wastewater). After reaching steady state, the coupled ME-EGSB-A/O system removed more than 95.0% of COD, 90.0% of NH₃-N and 80.0% of color, and the final effluent met the requirements of the national discharge standard (COD ≤ 500 mg L^-1, NH₃-N ≤ 45 mg L^-1 and chroma ≤ 70; CJ 343-2010, China). CONCLUSION: The coupled ME-EGSB-A/O system could treat the OTC production wastewater effectively. These findings have significant implications for a cost-efficient system in OTC production systematic treatment.