Fate of antibiotics in three distinct sludge treatment wetlands under different operating conditions.

Sludge treatment wetlands (STWs) have recently been used to treat surplus sludge. However, the distribution of antibiotics involved in the process has not been comprehensively investigated. This study aimed to evaluate the fate of two antibiotics, i.e., ciprofloxacin (CIP) and azithromycin (AZM) in STWs during the treatment of surplus sludge. Three pilot-scale STWs units—S1 with aeration tubes, S2 with aeration tubes and reed planting, and S3 with reed planting—were constructed and operated under feeding followed by resting periods. The results showed that antibiotic content in residual sludge decreased over time and unit S2 performed the best in terms of antibiotic removal. Planting reed considerably improved the antibiotic removal performance of the STWs. Biodegradation and absorption resulted in removal of most of the antibiotics in the test units. Less than 2% of the antibiotics was taken up by plants, whereas <5% of the influent antibiotics left the STW units through the drainage discharge. Overall, STW units contributed to effectively decrease CIP and AZM to 41–72% and 49–84%, respectively. Unlabelled Image • Sludge treatment wetlands (STWs) contribute to antibiotic removal from sludge. • Antibiotic removal is mainly due to biodegradation and substrate adsorption. • Plants significantly improved the ability of STWs to remove antibiotics. [ABSTRACT FROM AUTHOR]