Effect of adding low-concentration of rhamnolipid on reactor performances and microbial community evolution in MBBRs for low C/N ratio and antibiotic wastewater treatment

This study aims to explore the potential of low-concentration of rhamnolipid in efficient treatment of wastewater with poor biodegradability. Six lab-scale moving bed biofilm reactors (MBBRs) were applied to investigate the effect of rhamnolipid concentration (0, 20, 50 mg/L) on pollutants removal, biomass accumulation, microbial morphology and community evolution in synthetic low C/N ratio (3:1) and antibiotic (50 μg/L tetracycline) wastewater. 20 mg/L rhamnolipid treated groups exhibited significant increase (p < 0.05) of chemical oxygen demand (COD) removal and volatile solid (VS) content in both synthetic wastewater. Hydrogenophaga and Aeromonas were dominant in all reactors in which Aeromonas was positively correlated with the removal of COD and ammonia nitrogen (NH4+-N). Besides, Methyloversatilis became dominant only in 20 mg/L rhamnolipid treated groups and was positively correlated with VS. This study provides a novel and feasible strategy for treating poorly biodegradable wastewater by biofilm process with moderate amount of rhamnolipid.