Citric acid chelated Fe(II) catalyzed peroxidation for simultaneously improving sludge dewaterability and antibiotic resistance genes (ARGs) removal

Abstract Sludge contains large amounts of antibiotic resistance genes (ARGs), that reduce the efficacy of antibiotic therapies when transmitted to humans. However, conventional sludge treatment often fails to remove ARGs. Herein, critic acid chelated Fe(II) catalyzed peroxidation (CA-Fenton) was conducted to simultaneously improve sludge dewaterability and ARGs removal. As results, the CA-Fenton process exhibited significantly improved sludge dewatering performance and ARGs removal, in which the capillary suction time (CST), specific resistance to filtration (SRF) and cake moisture of sludge were reduced from 8.8 s·L/g, 5.8 × 1013 m/kg and 93.2% to 2.3 s·L/g, 5.8 × 1012 m/kg and 79.1%, respectively, and the removal efficiencies of 7 types-ARGs in sludge achieved over 90%. In addition, synergistic sludge dewatering and ARGs degradation mechanisms were elucidated with a suit of macro and spectroscopic evidence (high performance liquid chromatography-size exclusion chromatography (HPLC-SEC) and two-dimensional fourier-transform infrared correlation spectroscopy (2D-FTIR)). During CA-Fenton treatment, CA acidification enhanced permeability of the cell barrier in EPS, releasing intracellular ARGs into sludge bulk solution, which accelerated the ARGs degradation via CA chelated Fe(II) catalyzed H2O2 process. Meanwhile, destruction of secondary structure represented β-turn in proteins enhanced the hydrophobicity of EPS, which contributed the improvement of sludge dewaterability. The study not only proposed an efficient method to improve traditional Fenton oxidation for sludge treatment, but also provided a mechanistic basis for better understanding of the CA-Fenton process, and enable the harmless disposal for sludge.