Synergetic effect of nano zero-valent iron and activated carbon on high-level ciprofloxacin removal in hydrolysis-acidogenesis of anaerobic digestion

Ciprofloxacin is the most commonly prescribed antibiotic, and its widespread use poses threat to environmental safety. The removal of ciprofloxacin from contaminated water has remained a major challenge. The present study investigated adding nanoscale zero-valent iron (NZVI) and activated carbon (AC) on high-level ciprofloxacin removal in hydrolysis-acidogenesis stage of anaerobic digestion. The results showed that the degradation rate of ciprofloxacin increased from 22.61% (Blank group) to 72.41% after adding NZVI/AC with concentration of ciprofloxacin in effluent decreasing from 8.25 mg L−1 to 3.48 mg L−1. The volatile fatty acids (VFAs) yield increased by 173.7% compared with the Blank group. In addition, the NZVI/AC group achieved the highest chemical oxygen demand (COD) removal rate and acidogenesis rate. The microbial community analysis presented that hydrolytic and acidogenic bacteria and microorganisms related to degrading ciprofloxacin were obviously improved in the NZVI/AC group. Moreover, eleven transformation products and the main degradation pathways were proposed based on mass spectrometry information. In summary, the NZVI/AC addition supplied promising approach for ciprofloxacin wastewater treatment.