Vertical up-flow constructed wetlands exhibited efficient antibiotic removal but induced antibiotic resistance genes in effluent

Abstract

The intensive use of antibiotics results in their continuous release into the environment and the subsequent widespread dissemination of antibiotic resistance genes (ARGs), thus posing potential risks for public health. Although vertical up-flow constructed wetlands (VUF-CWs) have been widely used to treat wastewater in remote or rural regions, few studies have assessed the potential risks of ARG dissemination when VUF-CWs are applied to treat wastewaters containing antibiotics. In this study, the removal performance of two typical antibiotics (sulfamethoxazole (SMX) and tetracycline (TC)) and the fate of ARGs were evaluated in three lab-scale VUF-CWs. The results indicated that high removal efficiencies (>98%) could be achieved for both SMX and TC. However, the exposure of antibiotics resulted in harboring abundant ARGs (mainly sul- and tet-related genes), even with increasing abundances with operation time. The abundances of ARGs had a positive correlation with the accumulation of SMX and TC in different layers of VUF-CWs, where the tet and sul genes have the highest abundance in the bottom layer due to the highest antibiotic exposure concentration. Positive correlations were observed between the abundance of tet gene and antibiotic concentration in effluent. Although the effluent had lower abundances of the ARGs than that in the wetland media, the occurrence of ARGs in effluent might still pose risk for public health. Further studies are required to explore effective control strategies to eliminate ARGs from VUF-CWs.

Identification of Selected Antibiotic Resistance Genes in Two Different Wastewater Treatment Plant Systems in Poland: A Preliminary Study

“…The reports available in the literature suggest that, just like conventional WWTPs, CWs could be considered as hotspots for the spread of antibiotic resistance in the environment. Song et al [ 69 ] evaluated the fate of ARGs ( sul and tet ) in three lab-scale vertical flow CWs. They found out a positive correlation between abundances of ARGs and the accumulation of SMX and tetracyclines in different layers of CW substrate.…”

“…Although the effluent had lower abundances of ARGs than that in the wetland media, the occurrence of ARGs in effluent might still pose risk for public health. Moreover, the relative abundances of sul and tet genes showed a significant increase in all samples during the SMX and tetracycline treatment period [ 69 ].…”

Wetlands for wastewater treatment

“…In contrast, the removal of DCF was not affected by aeration (removal 50%) (Sochacki, Felis, Bajkacz, Nowrotek, & Miksch, 2018). On the other hand, vertical up-flow CWs exhibited efficient antibiotic (SMX and tetracycline) removal efficiencies (>98%); however, the exposure of antibiotics resulted in harboring abundant ARGs (Song et al, 2018). Similarly, removal of antibiotics (SMX) from ANNUAL LITERATURE REVIEW saline wastewater in CW mesocosms and CW microcosms was evaluated to test the influences of various salinity levels on SMX removal and it was revealed that high salinity level (EC at 30 mS/cm) significantly (p < .05) suppressed SMX removal in CW microcosms (Liang et al, 2018).…”

“…Moreover, He, Nurul, et al (2018) reported that the removal of ARGs was higher (in the range of 14% [Intl1] to 95% [sul2]) in a CW. In contrast, Song et al (2018) used a VFCW to remove the ARGs, which resulted in a significant increase in sul and tet genes with operating time and with significant correlations between 16S rRNA and ARG copy numbers in the effluent.…”

Treatment Processes for Microbial Resistance Mitigation: The Technological Contribution to Tackle the Problem of Antibiotic Resistance

“…Other considerations are necessary to apply these systems to remove antibiotics to reduce the supports' adsorption process. The long residence time of antibiotics or metals subjected to heterogeneous conditions within the CWs, along with the presence of other stressors, can also promote the microorganism's antibiotic resistance by selective pressure [117,118]. Zhang et al (2020) reported about the increase of sulfonamide resistance genes, as well as the increase of sulfamethoxazole concentration in the lower and the medium layers of the CWs [119].…”