Efficient carbon source recovery by ultrasound/sponge iron/persulfate system: implications for antibiotic resistance gene mitigation and transmission risk.

Highly transmissible antibiotic resistance genes (ARGs) constituted a major biosafety challenge in sludge resource recovery processes. This study provided a comprehensive evaluation of the mitigation and dissemination of ARGs throughout the continuum from carbon source recovery to utilization. The soluble chemical oxygen demand (SCOD = 556.07 mg/L) was 3.52 folds higher than raw sludge in US/sponge iron (Fe1)/PDS system, demonstrating excellent potential for carbon source recovery. The lysis efficiency of sewage sludge was extremely high (21.67%), accompanied by the release of propionic acid (15.7 mg/L), isobutyric acid (70.69 mg/L), n-Butyric acid (59.01 mg/L) and n-Pentanoic acid (51.71 mg/L). The oxygen-active substances dominated by sulfate radicals (SO4-) attacking large molecules with abundant electrons, improving the van der Waals free energy of the flocs, and releasing a large amount of organic carbon sources. Therefore, vanW-gene(vanl), adeF, qacG, sul2, vanY-gene(vanM) and LnuH decreased by 35%, 15.99%, 40.62%, 38.20%, 36.51% and 26.71%, respectively, with decreasing the relative strength of mobile genetic elements (MGEs). Furthermore, the carbon-utilization bioprocess exhibited a centralized functional architecture linking ARGs and MGEs with core microbial taxa (Thauera). This pattern suggested that carbon supplementation primarily reshaped host distribution rather than disrupting community structure, while potentially constraining indiscriminate ARG dissemination. Collectively, these findings provided mechanistic insight and risk-oriented support for the recovery and reuse of sludge-derived carbon sources.