Fate and Removal of Antibiotics and Antibiotic Resistance Genes in a Rural Wastewater Treatment Plant: A Microbial Perspective of Nature-Based Versus Advanced Technologies

Antibiotics (ATBs), antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) present an increasing threat/challenge to our environment and human health, resulting in increasingly strict wastewater management regulations through the revised Urban Wastewater Treatment Directive (UWWTD, 2024/3019/EU). This study evaluates a vertical-flow constructed wetland (CW) as a nature-based solution for removing ATBs, ARB, and ARGs from urban wastewater. The CW operated alongside two conventional quaternary treatments: granular activated carbon (GAC) and ozonation combined with GAC (O3 + GAC). Hydraulic conditions were kept stable across seasonal variations. Three antibiotics were quantified (through LC-MS/MS) in parallel to ARGs (through qPCR and metagenomics) and bacterial profiling (metabarcoding and plate counts). Results indicate that under the conditions tested (rural environment; UWWTP 13.000 p.e.), the CW achieves effective and stable removal of ATBs and ARGs. This study highlights the potential of nature-based solutions to match advanced quaternary treatments in removal performance and operational reliability, offering a sustainable and cost-effective means to reduce the spread of ATBs and ARGs via wastewater.