Pressure of high level acetaminophen on fixed biofilm and aerobic granule-based systems: Insights on nitrification performances, microbial responses and acetaminophen’s bio-degradation pathways

• AGSBR showed more tolerant to 5.0 mg/L acetaminophen (APAP) than FBSBR system. • Higher EPS, ALE and SA in AGSBR might contribute to its tolerance to 5 mg/L APAP. • 90% of microbial functional metabolisms in AGSBR had higher activity than FBSBR. • Pseudolactobacillus might be the potential APAP degrading bacteria. • The P-aminophenol and catechol were the main biological metabolites of APAP. Acetaminophen (APAP), a widely detected medical drug in water environment, which might cause toxic effects to ecological environment, was selected to explore its influence of high level (0.5 and 5.0 mg/L) on fixed biofilm sequencing batch reactor (FBSBR) and aerobic granule-based sequencing batch reactor (AGSBR). The nitrification performance in FBSBR was inhibited under the condition of 5.0 mg/L APAP, but it was not affected in AGSBR. The higher contents of extracellular polymeric substances, alginate like exopoly acids and sialic acid in AGSBR made it more stable than FBSBR system under the influence of 5.0 mg/L APAP. 90% of AGSBR’s functional metabolisms were enhanced after loading 5.0 mg/L APAP and kept high activity. 95.4% of APAP was removed in AGSBR system through adsorption (7.48%) and bio-degradation (87.92%). Furthermore, Pseudoclavibacter , a highly enriched bacteria only in AGSBR system (22%), might be the potential APAP degrading bacteria, which made APAP bio-degrade into P-aminophenol and catechol. AGSBR might have more advantageous than FBSBR system in treating pharmaceutical wastewater containing high level APAP.