Sorption and biodegradation of selected antibiotics in biosolids

Laboratory experiments were conducted to investigate the sorption and degradation of six antibiotics including Ciprofloxacin (CIP), Tetracycline (TC), Doxycycline (DTC), Sulfamethazine (SMZ), Sulfamethoxazole (SMX) and Clindamycin (CLD) in an aerobically digested biosolid. In the sorption experiment, CIP, TC, and DTC sorbed strongly, followed by CLD, while SMZ and SMX were only weakly sorbed to particles. An adsorption/desorption hysteresis was observed for nearly all the antibiotics to some extent. In the degradation experiment, the elimination of antibiotics, except CIP for which no degradation was observed, was found primarily attributed to biological degradation. For the degradation of TC, DTC, and CLD, a stable phase was achieved after preliminary degradation. We hypothesize that the nondegradable residuals are nondesorbable portions of sorbed antibiotics. From the results, other than SMX, all tested antibiotics can potentially survive biosolids storage periods and can be introduced into the environment following biosolids land application.