Impact of norfloxacin on microbial dynamics and methane production in anaerobic digestion of pig farming wastewater

Effects of norfloxacin (NOR) on the anaerobic digestion of swine wastewater were investigated. The results revealed that at concentrations of up to 0.5 mg L-1, there was an increase in methane production, probably due to the adapted microorganisms from sludge. From 1.0 mg L-1, an accumulation of volatile fatty acids (VFAs) was observed. However, only at 150 mg L-1 there was inhibition (similar to 13 %) of methane production. NOR decay kinetics experiments confirmed that adsorption was the main NOR removal mechanism, while biodegradation appears to be a secondary mechanism. At a dose of 0.1 mg L-1, the methanogenic archaea community was not inhibited by the presence of the antibiotic. Already at 10 mg L-1, Methanosarcinaceae family was reduced in the first hours, which limited methane production and led to VFA accumulation, followed by a recovery phase. These experiments indicate that only high doses of NOR were harmful to the microbial consortium.