The role of zero valent iron on the fate of tetracycline resistance genes and class 1 integrons during thermophilic anaerobic co-digestion of waste sludge and kitchen waste
2017
Gao, Pin | Gu, Chaochao | Wei, Xin | Li, Xiang | Chen, Hong | Jia, Hanzhong | Liu, Zhenhong | Xue, Gang | Ma, Chunyan
Activated sludge has been identified as a potential significant source of antibiotic resistance genes (ARGs) to the environment. Anaerobic digestion is extensively used for sludge stabilization and resource recovery, and represents a crucial process for controlling the dissemination of ARGs prior to land application of digested sludge. The objective of this study is to investigate the effect of zero valent iron (Fe⁰) on the attenuation of seven representative tetracycline resistance genes (tet, tet(A), tet(C), tet(G), tet(M), tet(O), tet(W), and tet(X)), and the integrase gene intI1 during thermophilic anaerobic co-digestion of waste sludge and kitchen waste. Significant decrease (P < 0.05) in the quantities of tet (except tet(W)) and intI1 genes was observed at Fe⁰ dosage of 5 g/L, whereas no significant differences (P > 0.05) were found for all gene targets between digesters with Fe⁰ dosages of 5 and 60 g/L. A first-order kinetic model favorably described the trends in concentrations of tet and intI1 gene targets during thermophilic anaerobic digestion with or without Fe⁰. Notably, tet genes encoding different resistance mechanisms behaved distinctly in anaerobic digesters, although addition of Fe⁰ could enhance their reduction. The overall results of this research suggest that thermophilic anaerobic digestion with Fe⁰ can be a potential alternative technology for the attenuation of tet and intI1 genes in waste sludge.
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