Impact of riverbed renaturalization on the ...

Mediterranean streams contain substantial proportions of wastewater treatment plant effluent, occasionally constituting the entire water flow. Here, we analysed the seasonal occurrence of 23 antibiotics (AB) and antimicrobial resistance (AMR) by tracking 3 marker genes and bacterial community dynamics in two wastewater effluent-dominated streams. One stream was renaturalized with meanders and vegetation, while the other was linear and had a low vegetation density. The concentration of ABs in the effluents ranged from 33 to 1,313 ng·L-1 during summer and 4 to 2,337 ng·L-1 during winter. The attenuation of ABs 3.5 km downstream varied depending on the compound, ranging from 42 to 88%. The half-lives of ABs obtained for the streams were 0.2 to 4.1 h in summer and 0.6 to 12.6 h in winter. Most ABs had a half-life of 45%. Overall, the results suggest that vegetation and meanders play an important role in the in-stream attenuation of ABs and AMRs.