Mitigation of Pharmaceutical Wastewater Toxicity in Anaerobic Reactors Using Metal-Modified Biochar

Anaerobic sequencing batch reactors (ASBRs) treating wastewater rich in ciprofloxacin (CIP) were supplemented with an Fe/Zn@biochar catalyst to improve their performance. ASBR4, with 100 mg Fe/Zn@biochar/g_VS, showed substantial increased efficiencies in removing COD and CIP, reaching 86.9 ± 5.8 and 80.9 ± 8.6%, respectively, compared to no biochar addition (25.2% and 51.1% higher, respectively). Likewise, biogas yield augmented from 0.17 ± 0.06 to 0.34 ± 0.02 L/g COD_removed owing to the boosted abundance of acetolactic methanogens, i.e., Methanosaeta and Methanosarcina, which increased from 0.4 and 1.6% in the control ASBR1 to 1.6 and 2.2% in ASBR4, respectively. Microbial enzymatic activities, including dehydrogenase and extracellular polymeric substances (EPSs), highly increased by 38% and >100%, respectively, aiding in biochar adsorption and microbial biodegradation synergy. Fe/Zn@biochar contributed to both CIP adsorption and biodegradation with percentages of 59.5 ± 4.9 and 34.7 ± 2.6%, respectively. The synergistic effect between the biotic and abiotic impacts of Fe/Zn@biochar reached 94.2 ± 7.2%, suggesting that the addition of Fe/Zn@biochar is a promising approach to enhance the CIP-remediation process.