Antibiotic contamination control mediated by manganese oxidizing bacteria in a lab-scale biofilter

Antibiotic micro-pollution is usually found at the ng/L-level in drinking water sources or discharge water of wastewater treatment plants. In this study, a novel approach mediated by manganese oxidizing bacteria (MnOB) in a biofilter was developed to control the pollution. The results indicated that the biogenic manganese oxide (MnO_x) produced during the oxidation of the feeding manganese ions could coat the surface of the filtering sand effecting the simultaneous removal of antibiotics. It was found that the removal of antibiotics is insured as long as the feeding manganese was well removed and was not influenced by the hydraulic loading. The growth rate of the MnOB group revealed that the antibiotic concentration at 50 and 100 ng/L promoted their activity, but it was inhibited at 500 and 1000 ng/L. The structure of the bacterial community was stable in the presence of antibiotics (50 ng/L), but their extracellular processes changed. The removal performance of the feeding manganese seemed to relate to the extracellular processes of the dominant bacterial genus. Moreover, the freshly formed MnO_x was a buserite-like material that was rich in Mn(III) and Mn(IV) (94.1%), favoring the degradation. The biofilter did not generate additional antibiotic resistant genes in the presence of antibiotics.