Removal of Chlortetracycline and Morphological Changes in Heavy Metals in Swine Manure Using the Composting Process

The widespread use of antibiotics and heavy metals in livestock farms results in large residues of antibiotics and heavy metals in the livestock manure. Composting technology can biodegrade residual antibiotics and solidify heavy metals. A pilot composting reactor was used to analyze the characteristics of chlortetracycline (CTC) removal at different antibiotic concentrations [0 mg·kg^-1 (CK), 10 mg·kg^-1 (T1), and 50 mg·kg^-1 (T2)]. Moreover, the morphological changes in heavy metals during the composting process were analyzed. After composting, no chlortetracycline was detected in the CK group and the antibiotics degradation rates of T1 and T2 groups reached 96.31% and 97.32%, respectively. The chlortetracycline degradation fits the pseudo-first-order kinetics model. Heavy metals can be solidified during the composting; thus, the bioavailable state of Cu and Zn (exchangeable state, reducible state) changed into the oxidation state and residues with apparent passivation formed. The correlation analysis showed that the removal of CTC showed strong positive correlations with the biological available Cu and Zn.