Degradation of macrolide antibiotic erythromycin and reduction of antimicrobial activity using persulfate activated by gamma radiation in different water matrices

Abstract

The degradation of macrolide antibiotic erythromycin (ERY) and the reduction of antimicrobial activity was performed using persulfate activated by gamma radiation in different water matrices. The results showed that the rate constant kobs of ERY degradation in γ ray-activated S2O82− (Gamma/PS) system increased by 6.5 times in deionized water, 5.0 times in groundwater and 1.4 times in treated wastewater, respectively. A significant improvement in mineralization rate was observed in Gamma/PS system, with 3.4–52% TOC reduction, compared to 0.9–25% in γ ray system. The results of antimicrobial activity of ERY against E. coli and S. aureus in the three kinds of waters showed that no antimicrobial activity to E. coli was observed at 1 kGy in Gamma/PS system, which required 6 kGy by γ ray alone. The inhibition to S. aureus was still observed at 10 kGy using gamma radiation in groundwater and treated wastewater, which disappeared in Gamma/PS system. The presence of organic substances inhibited ERY degradation more significantly than inorganic anions. In such cases, the ERY degradation rate was promoted by around 2 times and 12 times, respectively in the presence of peptone and glucose in Gamma/PS system. The 14-membered ring of ERY was destroyed by gamma radiation. Formic acid and acetic acid were detected and their yield was higher in Gamma/PS system. The γ ray-activated persulfate process is promising to treat ERY-containing water and wastewater.