Improving antibiotic resistance removal from piggery wastewater by involving zero-valent iron within an integrated anoxic-aerobic biofilm reactor

This study introduces zero-valent iron (ZVI) to enhance the removal of antibiotic resistance in piggery wastewater. Two integrated anoxic -aerobic biofilm reactors (IAOBRs) were operated simultaneously for 120 days, with one serving as a control reactor and the other as experimental reactor supplemented with ZVI. The experimental reactor demonstrated superior antibiotic removal efficiencies (89.8 +/- 4.5 %), eliminating 99.7 +/- 0.7 % of sulfonamides, 91.6 +/- 4.5 % of tetracyclines and 81.1 +/- 8.4 % of quinolones. The antibiotic resistance bacteria, antibiotic resistance genes (ARGs) and mobile genetic elements removal efficiency reached 0.69 - 1.74, 2.06 and 2.15 logs, respectively. In comparison to the control reactor, the activated sludge in the experimental reactor also experienced a reduction in total antibiotic concentrations by 57.58 +/- 19.99 %. The enhanced performance of the iron -mediated process in antibiotic resistance removal is attributed to the augmentation of enzymatic activity, biodegradation ability, and enrichment of specific microorganisms. The introduction of ZVI also modified the microbial community composition and decreased the potential hosts of ARGs. The proposed iron -mediated process greatly enhances antibiotic resistance removal from wastewater and mitigates antibiotic accumulation in activated sludge, offering new insights into wastewater biological treatment for eliminating antibiotic resistance.