Enhanced removal of antibiotics in wastewater by membrane bioreactor with addition of rice straw

Abstract

Antibiotics have been regarded as new emerging micro-pollutants due to their relatively stable structure and resistance to biodegradation. Rice straw, as a natural environmentally friendly biological carrier and available solid carbon source, was effective in improving the performance of membrane bioreactor (MBR). Parallel experiments of conventional MBR and two composite MBRs with addition of rice straw (unmodified or modified) were conducted to investigate the removal and biodegradation mechanisms of antibiotics. The results showed that the removal efficiency of COD and NH4+-N was both high irrespective of adding rice straw or not, while TN removal increased from 24.55% in conventional MBR to 44.48% in unmodified straw-added MBR and upto 54.47% in modified straw-added MBR. The addition of rice straw also significantly improved the removal of trimethoprim, with the removal of 40.82% in conventional MBR while 82.10% in unmodified straw-added MBR and 87.50% in modified straw-added MBR. However, the removal of sulfamethoxazole in three MBRs was so high that there were no obvious differences among the removal of 91.92%, 95.79% and 95.77%. Trimethoprim removal was achieved by both the nitrification co-metabolism and denitrification co-metabolism, while sulfamethoxazole was mainly biodegraded by nitrification co-metabolism.