Inhibition of Methane Fermentation by Antibiotics Introduced to Municipal Anaerobic Sludge

Annually, a few thousand tons of antibiotics and their transformation products (metabolites and degradation products) are introduced to wastewater treatment plants (WWTPs) as a result of human and animal excretion, or dispose of expired or unused medications. Antibiotics present in wastes might inhibit their treatment processes for instance during methane fermentation. In this study, β-lactams, tetracycline’s, fluoroquinolones, sulphonamides and metronidazole were selected as inhibitors of methane fermentation of sewage sludge collected from municipal WWTP. The experiments were performed in two series with different concentrations of antibiotics. The biogas production did not significantly differ between series, and was from 151.7 ± 18.9 mL/g VS (in the bioreactor with metronidazole addition—II series) to 208.3 ± 11.9 mL/g VS (in the bioreactor with amoxicillin addition—I series). In the control sample biogas production was 203.7 ± 21.1 mL/g VS. The methane content in all experiments was from 61.3 ± 2.1% to 66.4 ± 3.1%. The results indicated that microorganisms in anaerobic sludge from municipal wastewater are highly resistant to antibiotics in the tested concentrations. Antibiotic present in wastewater probably caused of antibiotic resistance in bacteria