Isolation and Characterization of an Erythromycin-Degrading Strain and Application for Bioaugmentation in a Biological Aerated Filter

Abstract

An erythromycin-degrading bacterium was isolated from the activated sludge of a sewage treatment plant (STP). Based on the morphological and physiological characteristics, the isolated strain was identified and named as Pseudomonas sp. ERY-E. In an inorganic salt medium inoculated at 1 % (v/v) of ERY-E strain containing 50 mg/L of erythromycin (ERY), the removal efficiency of ERY as high as 83.7 % was obtained under the optimum conditions with temperature of 30 °C, pH of 7.0, and 10 mg/L of yeast as the external carbon source. Subsequently, the ERY-E strain was used for bioaugmenting a biological aerated filter (BAF) to treat surface water containing low-concentration ERY. The influence of hydraulic retention time (HRT) and air-liquid ratio (A/L) on the performance of BAF was investigated. The average removal efficiencies of ERY and permanganate index (CODMn) were about 60.6 and 26.1 % in bioaugmented system (BAF2) and 26.9 and 26.0 % in unbioaugmented system (BAF1), respectively, under the optimum conditions with HRT of 4.0 h and A/L of 4:1 at steady state. Due to the stable removal of CODMn in BAF2 as compared with BAF1, it can be concluded that the introduction of ERY-E strain could collaborate with the indigenous microorganisms to attain a better ERY removal efficiency. As a result, the bioaugmented BAF method can be considered as an alternative technology for the treatment of surface water containing low-concentration emerging pollutants.